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[Display omitted] • New metal deposition method by EBID was used to grow thin films of W-based contacts. • Ohmic behavior was observed after thermal treatment at 800 K with a specific contact resistance of 2.74 × 10−4 Ω·cm2. • The Z-related contrast in HAADF microscopy allows to identify the W(C), Pt, and diamond layers. • STEM-EELS microscopy revealed WC formation on the W-diamond interface after annealing. The fabrication of ohmic contacts is a fundamental technological step toward the development and manufacture of reliable electronic devices. However, in the case of diamond-based devices, there is a lack of knowledge related to the formation of these types of contacts. While the role of interface carbide formation on refractory–metal/diamond contacts has been reported as a key mechanism for the thermal stabilization and optimization of ohmic behaviour; there is still a lack of knowledge, at the diamond/tungsten (W) interface, related to the structural and chemical characteristics versus electrical performance. To fulfil this lack, W onto boron-doped diamond contacts were fabricated on a p+ diamond layer by Electron-Beam Induced Deposition and followed by an annealing process. Then, W-diamond contacts were chemically, electrically, and structurally characterized at room temperature before and after thermal treatment. Once annealed, the Transfer Length Method (TLM) analysis revealed ohmic behaviour with specific contact resistance of 2.74 × 10−4 Ω·cm2. Electron Energy Loss Spectroscopy in Scanning Transmission Electron Microscopy (STEM-EELS) revealed tungsten carbide (WC) formation at the interface after annealing. So, a relation between WC formation and ohmic contact characteristics is demonstrated. [ABSTRACT FROM AUTHOR]

[Display omitted] • A model for energy-dependent XPS for depth profiling of chemical bonding. • N-Terminated diamonds obtained by Microwave Plasma show no sp2 defects. • A ∼5 % coverage of graphene-like islands is present atop the diamond surface. • The energy level of N surface states is determined within the diamond bandgap. • The high energy of the unoccupied surface states could help to stabilize NV- centers. Nitrogen-terminated diamonds hold promise for stabilizing near-surface NV− centers, which is essential for reliable quantum sensing. Among various surface preparation methods, microwave (MW) nitrogen plasma, known for its minimal surface damage, appears as the most effective choice. In this investigation, we explore the nature of nitrogen bonding of polycrystalline diamond (PCD) surfaces exposed to MW nitrogen plasma using X-ray Photoelectron Spectroscopy (XPS) depth profiling and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy at the C K - and N K -edges. XPS depth profiling with atomic resolution, achieved by varying the probing photon energy using synchrotron radiation and supported by a physical model considering the associated inelastic mean free path, suggests a surface of almost fully saturated nitrogen in two main bonding configurations of similar contribution and a low coverage of ∼5 % of graphene-like islands residing atop the nitrogen-terminated diamond surface. The thermal stability of these surface groups is monitored by in situ annealing up to 700 °C. The depth profiles reveal that nitrogen atoms do not diffuse in the diamond crystal, resulting in excellent diamond crystallinity in the first atomic planes below the surface. C K -edge NEXAFS analysis reveals the position of unoccupied surface states within the diamond bandgap, opening new perspective on the stabilization of near-surface NV− centers. [ABSTRACT FROM AUTHOR]

[Display omitted] • MeV Phosphorus ion implantation (1015 ions/cm2) induced moderate damage to diamond lattice without graphitization. • The simulated vacancy concentration in SRIM is significantly below the graphitization threshold, consistent with experimental observations. • Validation of simulated internal defects via Raman and PLspectra post-annealing at 400 °C: PL spectra confirmed GR1 centers' presence. • Significantly recovers damage after 900 °C annealing, as evidenced by GR1 center disappearance and enhanced NV center characteristics. The purpose of this work is to provide a novel perspective for investigating the damage of diamond surfaces implanted by MeV phosphorus (P) ions and recovery of the surfaces after high-temperature annealing. SRIM simulation and low-temperature luminescence spectroscopy were performed to analyze the properties of the samples comprehensively. The results revealed that a certain degree of diamond lattice damage was caused without graphitization by the irradiation of 1 MeV P ions with a fluence value of 1015 ions/cm2. The SRIM simulation revealed that the ions that were implanted into the lattice collided with carbon atoms. These ions stopped at a depth of approximately 0.55 μm and generated intrinsic diamond defects on the diamond near the surface. The simulated defects were confirmed by the appearance of neutral single vacancy (GR1) centers in the photoluminescence (PL) spectrum after annealing at 400 °C. In addition, the annealing behavior of optical centers at 900 °C indicated significant damage recovery, including the disappearance of GR1 centers, combined with the increased intensity, slightly blue-shifted peak position, and narrowed FWHM of the nitrogen-vacancy (NV) center. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effects of annealing and cooling on the growth of graphene were systematically characterized. • The multi-layered graphene on diamond substrate are flatness and have high electron mobility. • The ohmic contact of graphene/Au on BDD was better than Ti/Au. In this paper, graphene with good uniformity was successfully grown on (1 0 0)-orientation single crystal diamond substrate directly by regulating the annealing and cooling temperature. A medium annealing temperature of 1000 °C and duration of 20 s can trade-off the thickness and uniformity. In addition, the stress condition and thickness of graphene also present a dependence on cooling temperature. Under the cooling temperature of 500 °C, the multi-layered graphene (30 nm thickness) with high electron mobility (737 cm2/Vs at room temperature) was obtained. The surface roughness was 2.36 nm for the graphene layer and 0.85 nm for the etched diamond substrate, indicating a good surface flatness. By comparing with the Ti/Au electrode, it was found that the graphene directly synthesized on diamond presented improved ohmic contact with the diamond substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface oxidation of a single-crystal diamond (100) was conducted using four different oxidation methods. • The oxidised samples underwent a systematic study utilising state-of-the-art surface-science techniques. • Experimental findings demonstrated notable variations in the electronic structure of O-terminated diamond (100) surfaces, dependent on the specific oxidation technique employed for surface treatment. • The variations in work function values observed in the oxidised samples were significantly influenced by the presence of oxygen-containing functional groups. The surface modification of diamond holds crucial significance in various applications, such as electron emission devices, Schottky diodes and field-effect transistors. Oxygen termination is one of the most common termination types, where three distinct carbon-oxygen bonded configurations (i.e. ether, ketone and hydroxyl) are typically found concurrently on the surface. An unanswered question in this context is whether each oxygen-containing functional group influences the tuning of the surface electronic properties of diamond. Here, we systematically explore the surface oxidation of (100)-oriented single-crystal diamond using four different oxidation methods: oxygen plasma exposure, UV-ozone irradiation, acid treatment and oxygen-gas thermal cracking. The relative concentration of the oxygen functional groups varies significantly depending upon the oxidation technique used. Specifically, O 2 -plasma and thermal-cracking methods result in higher percentages of ether configurations (52.1% and 71.5%, respectively), whereas UV-ozone and acid-oxidation treatments preferentially yield ketone (47.9%) and hydroxyl (51.3%) groups. Additionally, employing state-of-the-art surface-science techniques, the surface electronic structure of each oxygenated sample is revealed. These experimental findings show that specific oxidation methods significantly alter the work function of all four oxidised surfaces, being measured in the range of 4.65 eV and 5.79 eV. This study paves the way towards selective tuning of the oxygen surface configurations suitable for fabricating diamond-based energy materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface graphitization of diamond is achieved through thermal annealing. • Graphite/diamond pattern is selectively etched by hydroxide ion treatments. • The structure transformation is investigated via AFM, XPS, Raman and TEM. • The specific contact resistance is obtained by TML model. Ohmic contacts with low specific contact resistance are necessary for fabrication of diamond electronic devices. This work reports that graphite/diamond ohmic contacts can be obtained by thermal annealing of diamond, patterned by hydroxide ion treatment. Surface graphitization of diamond is achieved through rapid thermal annealing at 1050 °C in vacuum. The thickness of graphite layer is found to be dependent on the duration of annealing with an approximate rate of 3.3 ∼ 3.6 nm/minute. The alteration in surface structure is analyzed using Raman spectra, showing a continuously enhanced G peak with increasing annealing time. Early stages of graphitization are discovered by X-ray photoelectron spectroscopy, after annealing diamond samples for merely 0.5 ∼ 2 min. Additionally, a distinct atomic interface between graphite and diamond is observed via cross-sectional transmission electron microscopy. Further, the surface graphite is selectively etched by hydroxide ion treatments, protected by gold patterns. In the end, the specific contact resistance of the graphite/diamond contact is determined to be 2.53 × 10-4 Ω cm2 employing the transmission line model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen terminated N-UNCD exhibits low capacitance and faradaic photoresponse. • Oxygen terminated N-UNCD exhibits high capacitance and capacitive photoresponse. • Unlike single-crystal diamond, both surfaces have a positive electron affinity. • Hydrogen-terminated N-UNCD possessed the lowest electron affinity at + 0.4 eV. • Differences in valence band edge positions can explain electrochemical reactivity. In recent years, various forms of nanocrystalline diamond (NCD) have emerged as an attractive group of diamond/graphite mixed-phase materials for a range of applications from electron emission sources to electrodes for neural interfacing. To tailor their properties for different uses, NCD surfaces can be terminated with various chemical functionalities, in particular hydrogen and oxygen, which shift the band edge positions and electron affinity values. While the band edge positions of chemically terminated single crystal diamond are well understood, the same is not true for nanocrystalline diamond, which has uncontrolled crystallographic surfaces with a variety of chemical states as well as graphitic grain boundary regions. In this work, the relative band edge positions of as-grown, hydrogen terminated, and oxygen terminated nitrogen-doped ultrananocrystalline diamond (N-UNCD) are determined using ultraviolet photoelectron spectroscopy (UPS), while the band bending is investigated using photoelectrochemical measurements. In contrast to the widely reported negative electrode affinity of hydrogen terminated single crystal diamond, our work demonstrates that hydrogen terminated N-UNCD exhibits a positive electron affinity owing to the increased surface and bulk defect densities. These findings elucidate the marked differences in electrochemical properties of hydrogen and oxygen terminated N-UNCD, such as the dramatic changes in electrochemical capacitance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A micro- to nano-scale etched topography is modelled on diamond substrate along crystal orientation. • The etched structure formation procedure is related to thermal oxidative and graphitization. • The structured size is subject to crystalline orientation, environmental temperature and catalytic metal element at the macro scale. • The structural size on substrate varies between the (1 0 0) and (1 1 1) surfaces, with an increasing trend as it approaches the (1 1 1) surface. • The micro- and nano-scale structures of diamond substrate may be transferred each other by the etching along crystal orientation. Substrate functionalization of diamond semiconductors rely on micro- and nano-topographical shapes and dimensions. However, an efficient and controllable fabrication is challenging due to its high hardness. In this study, a micro- to nano-scale etched topography model is proposed on the machined diamond substrate related to graphitization along crystal orientation. The objective is to explore how to control the structured dimensions based on atomic scale removal. First, the formation model of the etched structure was established in relation to thermal oxidation and graphitization, etc. Then, experiments were conducted to compare the structure size of the natural crystal surface. Finally, the etched structure dimension on the substrate was theoretically analyzed and experimentally characterized. It is shown that the dimension of etched structures depends on the rate of C atoms escaping layer by layer as CO/CO 2 molecules with graphitization. The oxidative etching rate shows an increasing change in temperature. The degree of graphitization is enhanced as it approaches the (1 1 1) surface. At the macro scale, the structured size is subject to crystal orientation, environmental temperature, and catalysis. As a result, the micro- and nano-scale structures of the diamond substrate may be transferred to each other by the etching along crystal orientation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using the low-density crystal seeding method, diamond particles containing silicon color centers were prepared on a single-crystal silicon substrate. • Controlled preparation of arrayed diamond nanopillars was achieved by an anodized aluminum oxide template combined with a metal dewetting process. • The nanopillars, prepared with uniform diameter and regular arrangement, enhance the luminescent performance of diamond color centers. Diamond nanopillars can improve the photon emission efficiency of diamond color centers. In this study, a low-cost and controllable method for preparing array nanopillars, which is different from photolithography, is proposed. Single-crystal diamond particles containing silicon color centers were prepared by low-density crystal seeding method. Array metal masks of different sizes were prepared on the surfaces of the diamond particles by controlling the metal film deposition time, passing through anodized aluminum oxide array holes, and cooperating with the metal film dewetting process. Subsequently, diamond array nanopillars of different sizes were prepared using oxygen plasma etching. The fluorescence detection indicates that the fluorescence intensity of silicon vacancy color centers in the nanopillar arrays is enhanced by 14.4 times compared to that inside diamond particles. The effects of the color center depth and nanopillar diameter on the excitation efficiency, Purcell factor, photon emittance, and total fluorescence efficiency of the color center in diamond array nanopillars were simulated by the finite-difference time-domain method. It was found that the total fluorescence efficiency of the color center could be up to 89 %, which was 20 times higher than that of the diamond bulk. This provides solutions for improving quantum communication, quantum detection efficiency, and low-cost device preparation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Achieving hydrophilic bonding of Si and diamond by depositing a thin AlN interlayer. • Ar ion-beam treatment can modify the surface morphology to create a more realistic contact area. • The native oxide and hydrolysis layers on the AlN surface prevented hydrophilic bonding reactions. • Low-temperature bonding is realized by interfacial co-hydrolysis to generate boehmite. As a III-nitride, AlN exhibits high thermal conductivity, excellent insulation, and low thermal expansion. Therefore, AlN is an alternative to the insulating layer in conventional Si-on-insulator (SOI) systems to solve the problem of severe self-heating effects caused by the poor thermal conductivity of buried oxide (BOX, SiO 2) layers. This is particularly true for high-power integrated circuit and micro-electro-mechanical system fabrication. However, heat transfer also depends on the bottom Si substrate. With the highest thermal conductivity (≥2000 W/mK) among bulk materials, diamond is a highly attractive option to replace conventional Si substrates. Herein, we describe a low-temperature vacuum-free hydrophilic bonding method based on a thin AlN interlayer to prepare a single-crystal Si layer on a polycrystalline diamond. Through suitable Ar ion-beam activation, the surface nanomorphology and chemical state can be simultaneously modified. Increasing the real contact area and removing the surface heavy oxygen layer are critical factors for achieving complete bonding. Moreover, the relatively mild deposition and bonding conditions of AlN make it compatible with the complex CMOS transistor process and could enable the more flexible integration of diamond into 3D chip packages in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • High thermal conductivity of 575 W/mK was obtained with low-volume of continuous diamond skeleton at Cu-matrix composites.. • W nanolayers were evaporated to improve the wettability between Cu and diamond. • The diamond skeletons formed 3D continuous high-efficiency heat transport pathways inside the composite. • The overall thermal transfer performance was significantly enhanced, achieving high thermal conductivity with low diamond volume. The weak interfacial bonding strength between diamond and copper intrinsically restricts the enhancement of the thermal conductivity of diamond particles/copper composites (abbreviated as DP/Cu). This work first proposed the diamond skeleton (DS) as the reinforcement element rather than dispersed diamond particles. The tungsten (W) transition layer (c.a. ∼300 nm thick) having adequate thermal expansion coefficient was sputtered onto the surface of DS via vacuum evaporation technology, aiming to improve the wettability between diamond and copper and accordingly increase the thermal conductivity of DS/copper composites extruded by gas pressure infiltration technique. The experimental results show that the coated W layer can effectively improve the wettability of the diamond surface and reduce the wettability angle from 108.6° to 13.2°. Raman and XRD spectra show that the W layer can, to a great extent, prevent the graphitization of the diamond surface. SEM and EDX evidence a continuous heat transfer path of DS inside the composites. The thermal conductivity of the DS/Cu composite with low diamond loading of 18.4 vol% reaches 575 W/mK, 43.3% higher than that of pure Cu. Finite element simulations show that DS exhibits excellent heat transfer characteristics, agreeing well with the thermal conductivity simulation results. [ABSTRACT FROM AUTHOR]

This work builds varied nanostructures on the boron-doped diamond (BDD) film by changing the surface status of the silicon (Si) substrate in a facile method and investigates the influence mechanism of surface morphology of the substrate on the capacitive performance of the formed Si/BDD electrode. The BDD electrodes with different nanostructures are synthesized by hot filament chemical vapor deposition (HFCVD) technique on the etched Si wafers, which are etched in HF (5 M)/AgNO 3 (0.035 M) aqueous solution (55 °C) from 0 to 50 min. Results show that it forms surface structures and contents of doped boron atom and sp 2-C bonds of BDD electrode on the Si substrates with etching time varied. The varying structures and compositions may induce changes in capacitive performance of the BDD electrode. In 0.1 M Na 2 SO 4 aqueous solution, sample D at etching time of 30 min obtained the biggest capacitance of 103 mF/cm2 at current density of 0.1 mA/cm2. In particular, the capacitance is 27 times higher than that of sample A without etching. Sample D also has retention of 80% after 3000 cycles, indicating a dependable stability of the electrode. A mechanism is then proposed how surface morphology of Si substrate affects the capacitance properties of the Si/BDD electrode. Unlabelled Image • Boron doped diamond (BDD) electrode with nanostructure was synthesized in a facile method. • Capacitance of electrode at etching time of 30 min was 27 times higher than the bare one. • Superior cycling durability of 80% retention after 3000 cycles was observed. • Influence of substrate surface morphology on capacitive behavior of formed BDD electrode was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Subnano-scale roughness of Gradia surface was acquired by CMP. • Subsurface damage of lattice distortion was incompatible for graphite and diamond in Gradia. • Chemically reacted graphite phase was more than the diamond phase during CMP of Gradia. • Diamond phase was chemically softened to graphitic phase for rapid material removal. The novel graphite/diamond composite (Gradia) possesses semiconducting instinct characteristics with controllable resistivity. Surface finishing plays a crucial role in using Gradia. However, controlled removal of the Gradia surface is challenging because physical and chemical properties differ between the graphite and diamond components. The impact of incompatibility on the material removal of Gradia is unclear. This study employed chemical mechanical polishing (CMP) to finish the Gradia surface with K 2 FeO 4 oxidant. First, the sub-nano-scale roughness of the Gradia surface was attained by applying optimized polishing parameters. Then, the polished subsurface was examined. The incompatible graphite and diamond lattice distortion was the primary damaged mechanism rather than amorphization. The chemical reaction in CMP was analyzed with X-ray photoelectron spectroscopy and reactive molecular dynamics simulation. The carbon atoms formed a variety of chemical groups with the oxidizing of hydroxyl. The chemical activity of the graphite phase was superior to the diamond phase, leading to more types of reaction and a higher percentage of products. In the material removal stage, experimental observations and simulation analyses revealed that the diamond of sp3-carbon transformed to sp2-carbon, softened, and subsequently removed together with the graphite by abrasive scratching. [ABSTRACT FROM AUTHOR]

[Display omitted] • A comprehensive investigation of Ga 2 O 3 /diamond heterostructures, including microstructure, chemical state, and thermal conductance characteristics, was conducted by combining theory with experiments. • Deep etching analysis revealed the presence of a non-diamond sp2 peak near the interface of the heterostructure. • The heterostructure exhibited a staggered (type Ⅱ) band alignment. • The thermal conductivity of amorphous Ga 2 O 3 was 5.13 W/(m·K) and the TBC of Ga 2 O 3 /diamond was 19.22 MW/(m2·K) from TDTR measurements. In this work, the characteristics of the gallium oxide (Ga 2 O 3)/diamond heterostructure were thoroughly examined after the preparation of Ga 2 O 3 thin film on bulk diamond via atomic layer deposition. The X-ray diffraction (XRD) analysis revealed the Ga 2 O 3 film amorphous and diamond polycrystalline. The atomic force microscopy (AFM) mapping displayed remarkably smooth surfaces of the Ga 2 O 3 film and diamond substrate (RMS of 0.184 and 0.508 nm, respectively). The scanning electron microscopy (SEM) images showed conspicuous grains formed on the diamond, and small crystallites on the surface of the film. The optical characteristics were investigated via spectroscopic ellipsometry (SE) and UV/Vis/NIR spectrophotometer. Raman spectroscopy suggested a sharp diamond-related (sp3) peak and an extremely weak bulge band around 1350–1620 cm−1. X-ray photoelectron spectroscopy (XPS) analysis indicated Ga 2 O 3 /diamond heterojunction to be staggered (type II) band alignment with valence band and conduction band offsets of around 1.18 eV and 2.09 eV, respectively. Moreover, according to time-domain thermoreflectance (TDTR) measurements, the thermal conductivity of Ga 2 O 3 and the thermal boundary conductivity of the heterointerface were 5.13 W/(m·K) and 19.22 MW/(m2·K), respectively. These findings not only demonstrate the feasibility of Ga 2 O 3 -on-diamond hetero-integration but open up new prospects for the design and physical analysis of Ga 2 O 3 /diamond-based devices in the future. [ABSTRACT FROM AUTHOR]

A thorough study on sp3 to sp2 carbon conversion in undoped and boron-doped diamond (BDD) thin (≈ 500 nm) layers leading to the desired sp2/sp3 carbon ratio and lateral distribution, which utilizes boron atom incorporation and infrared (IR) material laser processing has been performed. Polycrystalline as-grown (AG) or chem-mechanically polished (CMP) undoped diamond/BDD layers were investigated with respect to boron content and laser wavelength (800, 1030 nm). Boron incorporation leads to an increase in IR optical absorption and reduction of required energy fluence (F th ≈ 1 J cm−2) needed for sp3 to sp2 carbon conversion. Raman spectroscopy was performed to identify carbon conversion stages and to tailor the ideal parameters for other IR laser sources and required sp2/sp3 carbon ratio. Electrochemical parameters (Δ E p and I Ap / I Cp ratio) were obtained from cyclic voltammetry measurements of outer-([Ru(NH 3) 6 ]3＋/2＋) and inner-([Fe(CN) 6 ]3−/4−) sphere redox markers. Values of Δ E p and I Ap / I Cp are mainly influenced after conversion of 10% of sp3 to sp2 carbon. This trend is most pronounced for the [Fe(CN) 6 ]3−/4− redox marker, by decrease or increase of these parameters on AG or CMP BDD electrodes respectively. Electrochemical findings were supported by electrochemical impedance spectroscopy where R ct keeps the same trend as Δ E p values and double layer capacitance profoundly increases between 10 and 25% of surface conversion. [Display omitted] • IR laser processing of boron-doped diamond films enhances elchem performance. • Controlling sp2 carbon distribution over laser-processed surface. • Desired spot shaping with sp2 carbon at low laser fluence regime. • Electroactivity of sp2 carbon area confirmed on as-grown "undoped" BDD. • When sp2 carbon area < 25%, sp3 carbon phase dominates electrochemical activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The graphitization of the diamond (1 0 0) surface is elucidated by the first-principles calculation. • The chemisorption of Fe atoms varies the connections between the sixfold chair ring structures rather than breaking them. • The migration activation energy and movement direction are correlated with the anisotropy of the material removal rate. Studying diamond graphitization is a crucial issue in ultra-precision machining because it sheds light on the reason for material removal during polishing. The polishing disc made of cast iron is usually used to process diamonds, and a high-quality surface can be obtained. However, the graphitization mechanism induced by iron (Fe) is still obscure. This paper employs the density-functional theory (DFT) method to elucidate the mechanism by which Fe induces diamond graphitization. The results demonstrated that Fe atoms at the metastable adsorption sites (P3) on the surface could change some C–C interactions between layers. Notably, multiple Fe atoms at the P3 sites could alter the region of surface graphitization and the structural dissociation direction. The surface area close to Fe atoms became stable, while the surrounding surface areas were susceptible to oblique dissociation into graphite-like structures. Moreover, we speculated that the material removal rate was related to the moving activation energy of Fe atoms. Based on the charge-transfer and microstructural evolution, the phenomenon of Fe-atom-induced diamond graphitization was attributed to varying the connections between sixfold chair rings and promoting their weakening and dissociation rather than breaking the structure of sixfold chair rings. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti-coated diamond wheel was used to mechanochemically grind diamond film. • Vacuum micro-evaporation coating technique was employed to deposit Ti on diamond. • A diamond-TiC-Ti structure was formed on micro-diamond abrasives. • Ti coating on protruding diamond abrasives enhanced material removal rate. • Ti reacted with diamond film and facilitated graphitization at contact locations. The outstanding hardness and wear resistance of diamond materials pose significant challenges in their grinding processes for semiconductor substrate materials. To overcome this, a mechanochemical effect-based approach is used, which employs a grinding wheel comprising titanium (Ti)-coated diamond abrasives. A uniform Ti coating is vacuum-evaporated onto micrometer-scale diamond abrasives. The coating layer forms a diamond-TiC-Ti structure extending from the diamond matrix to the Ti coating direction. The material removal rate (MRR) of the DF is significantly increased as a result of the protruding active Ti coating on the diamond abrasives reacting with the DF at the interface contact locations. Increasing the grinding speed from 300 rpm to 700 rpm under a fixed grinding pressure of 300 N results in an MRR increment from 32 nm/min to 913 nm/min. Similarly, maintaining a grinding speed of 600 rpm while increasing the grinding pressure from 300 N to 600 N leads to an MRR increase from 388 nm/min to 1662 nm/min. The primary mechanism behind material removal is the reaction between the Ti coating and the DF, as well as the graphitization of the DF. [ABSTRACT FROM AUTHOR]

[Display omitted] • An innovative diffraction prediction model is firstly proposed and validated to describe the diffractive spectrum of atypical gratings in UPC processes. • The deterministic rendering of structural color is demonstrated by texturing three groups of blazed gratings with controllable topography. • The optimal grating topography design is given for maximizing the region size of color gamut using the novel concept of average saturation. • The sound framework for UPC-induced structural color is established by linking the cutting process parameters to final optical performance. Ultra-precision diamond cutting (UPC) has been recently proposed for fast generation of nano-gratings to render diffractive structural color on various metallic surfaces. However, the complex nanoscale generation mechanism and atypical grating topography provide the significant challenges for deterministic rendering of structural color with standard representations. In this paper, an innovative diffraction prediction model is firstly proposed to describe the diffractive spectrum of atypical gratings under the full considerations of cutting process parameters, double working facets, material optical properties and environmental conditions. The standard CIE 1931 chromaticity diagram for grating-induced structural color is released for color gamut determination and optimization, where the color gamut range is defined by a novel concept of average saturation. The experimental results demonstrate the deterministic generation of three groups of nano-gratings with desired 3D topography, of which the measured angle-dependent diffractive spectrum and rendering color attributes show good agreements with theoretical results. Moreover, the new topography-modulation based strategies for achieving maximal color gamut and manipulating the ternary color attributes are clarified. The outcome of this paper lays the scientific foundations for deterministic rendering and performance enhancement of structural color enabled by UPC processes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The a-C layers are introduced to regulate the vibrational bridging effect. • The C-O bonds are modified to regulate the interfacial bonding effect. • The G is increased by inserting an a-C interlayer between Cu and diamond. • Vibrational bridging effect overwhelms interfacial bonding effect in improving G. Introducing an interlayer is an effective method to improve the interfacial thermal conductance (G) of highly mismatched Cu/diamond interface. However, the relative role of interfacial bonding effect and vibrational bridging effect of the interlayer is still not clear. Herein, we introduce amorphous carbon (a-C) layer by Ar ion bombardment, oxygenated a-C layer by Ar/O 2 mixture ion bombardment, and C-O bond by acid treatment at the Cu/diamond interface to regulate the interfacial bonding effect and vibrational bridging effect. The G of Cu/diamond is increased by 44% with increasing interfacial bonding strength from 12 mN to 17 mN and then is independent on interfacial bonding strength above 17 mN, which mainly comes from the interfacial bonding effect. Compared with the as-cleaned Cu/diamond interface, a 35% increase of G is obtained by inserting a 4.5 nm-thick a-C interlayer between Cu and diamond, which mainly comes from the vibrational bridging effect. The vibrational bridging effect overwhelms the interfacial bonding effect in improving the G of Cu/diamond interface when the interfacial bonding strength is relatively high. The findings give insights into the mechanisms dictating heat transfer of highly mismatched metal/non-metal interface and provide a new avenue for improving the G of Cu/diamond interface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface graphitization appeared at low laser energy without D&G Raman peaks. • highly oriented graphite and poor-quality diamond areas were observed by TEM. • The specific contact resistance of 7.83 × 10-5 Ω cm2 was acquired by TML. • The barrier height of graphite/diamond contact was obtained to be 0.54 eV. Graphite was formed by in-situ structural conversion from sp 3 to sp 2 hybridized carbon via KrF excimer. The surface morphology of diamond was changed to nanoparticles after laser irradiation. Raman peak related to amorphous carbon emerged after laser treatments with energy of 10 ∼ 25 mJ cm−2. X-ray photoelectron spectroscopy exhibited that surface graphitization could take place under low laser energy of 2 mJ cm−2. The structural transformation of diamond after laser irradiation was further studied by cross-sectional transmission electron microscopy (TEM) analysis. The TEM results displayed that the diamond/graphite interface was gradually transformed from diamond to graphite, and the transformation process was verified by molecular dynamics simulations. The specific contact resistance of 7.83 × 10-5 Ω cm2 for the diamond/graphite structure was acquired by transmission line model. Meanwhile, the barrier height of the graphite/diamond contact was obtained to be 0.54 eV. In the end, an all-carbon deep-ultraviolet photodetector with diamond/graphite structure was developed. The all-carbon photodetector exhibited relatively high responsivity of 15 mA/W under 220 nm illumination, and a fast transient response of 86 μs. [ABSTRACT FROM AUTHOR]

By theory calculation, a new orthorhombic form of diamond has been proved to exist. In this work, the orthorhombic diamond is clearly observed in the multiarc ion-plated varying-C VN films and the effect of C content on the microstructure, mechanical and tribological properties of varying-C VN films were studied in detail. The C doping results in the mechanical and tribological properties' improvement, together with the decrease of surface roughness and residual stress, and with the increase of C content, the scratch-resistance and wear-resistance capacities increase. The orthorhombic diamond phase only appears in VCN film with 10.97 at.% C, leading to that this VCN film has a relative low room-temperature friction coefficient (~0.56) compared with other films (~0.70), due to the easy-shear layered atomic structure. The VCN film containing 19.14 at.% C with the highest H / E and H 3/ E 2 ratios of 0.052 and 0.091 GPa has the minimum wear rate (0.53 × 10−14 m3 N−1 m−1), 82% lower than that of VN film (2.89 × 10−14 m3 N−1 m−1), due to the valid assembly of VN, VC and amorphous C phase with perfect balance of hardness and toughness. However, against Al 2 O 3 grinding ball, the main wear mechanisms of all varying-C VN films are adhesive wear and oxidative wear. Unlabelled Image • A new orthorhombic form of diamond was synthesized successfully in experiment. • The orthorhombic diamond phase only appeared in the film with 10.97 at.% C. • Easy-shear layered atomic structure of orthorhombic diamond leads to the lowest COF. • The film with 19.14 at.% C has the best mechanical and tribological properties. • The main wear mechanisms of all films are adhesive wear and oxidative wear. [ABSTRACT FROM AUTHOR]

Abstract Although nano polycrystalline diamond (NPD) is found with hardness equal to, or even higher than that of single crystal diamond, there are still some controversies about its mechanical responses as well as the plastic deformation mechanisms during the indenting processes. Through molecular dynamics simulations, we have investigated the effects of grain size and temperature on the indentations of NPD. Our results indicate that when the grain size is smaller than 10 nm, NPD would soften as the grain size decreases. For the studied grain sizes of 5, 7, and 10 nm, plastic deformations are resulted from the dislocation propagation mode and the atomic disordering mode. For NPD with the studied grain size of 2 nm, its plastic deformation is mainly determined by the atomic disordering of the diamond grains. Our simulations reveal that higher temperatures result in the softening of NPD, and the plastic deformation mechanisms at high temperatures are basically the same with that at 300 K. The results presented in this work not only provide an answer for the questions about the grain size and temperature effects on the mechanical responses of NPD, but also offer insights into plastic deformation mechanisms of NPD, which could provide reference data for the potential applications as well as the design of novel nano structured superhard materials. Highlights • Dislocation activity dominates the plastic deformation of NPD with large grain sizes. • Atomic disordering dominates the plastic deformation of NPD with small grain sizes. • NPD would soften as the grain size decreases or the temperature increases. • The elastic recovery ability of NPD decreases with the reduction of grain sizes. [ABSTRACT FROM AUTHOR]

Abstract In this article the diamond-like carbon films have been prepared by the strategy of the glancing angle deposition using unbalanced magnetron sputtering technique. It is found that the structure and the residual stress of the films are strongly dependent on the deposition angle. Of particular interest is that the stress of the films significantly transforms from compressive to tensile state as a function of the deposition angle, which is attributed to the result of the competition and mediation between compressive stress due to surface capillary forces of the island surface and tensile stress due to the coalescence of the islands during Volmer-Weber growth of the films. Based on this mechanism, the nearly stress-free film with desirable performance can be prepared at the proper deposition angle. The correlation between the residual stress and the atomic-bond structure also reveals that the stress transition is not only related to the sp2-bonded carbon content, but also closely to the changes of the heptatomic and pentatonic rings in the carbon network. This work demonstrated herein will provide a promising route to prepare the stress-free diamond-like carbon films with desirable performance. Graphical abstract Unlabelled Image Highlights • The DLC films have been prepared using the strategy of glancing angle deposition. • The film stress transforms from compressive to tensile state with deposition angle. • The nearly stress-free DLC film can be obtained within the stress transition region. • The mechanism of stress transition is explained in view of growth process of films. • The results reveal the correlation between the stress and atomic-bond of the films. [ABSTRACT FROM AUTHOR]

Highlights • The C/C multilayer can withstand the contact stress of ∼3.65 GPa with low wear rate. • The wear rate of C/C multilayer is 10 times lower than that of other DLC coatings. • The load bearing capacity of C/C multilayer is double that of DLC coatings from literature. • Besides hardness, the toughness also contributes to the wear resistance. • The C/C multilayer has better toughness than that of single layer coatings. Abstract Diamond-like carbon (DLC) coatings are widely used in tribological applications because it can provide high hardness and low friction coefficient. However, hydrogen-free DLC coatings tend to fracture and delaminate where high contact stresses (>1 GPa) are required. We proposed that the carbon/carbon (C/C) multilayer may have the potential for tribological applications under high contact stresses. In this study, C/C multilayer coatings consisting of alternate soft-layer and hard-layer were deposited using unbalanced magnetron sputtering technique. The effect of multilayer architecture (the ratio of hard-layer to soft-layer and bilayer thickness) on tribological behavior was investigated. The tribological performance at different high contact stresses (1.82 GPa, 2.30 GPa, 2.89 GPa and 3.65 GPa) was evaluated by a ball-on-disc tribometer. The C/C multilayer coatings can withstand the maximum contact stress of ∼3.65 GPa with low wear rate. In contrast, the single layer hard DLC failed when the stress is higher than 2.30 GPa. The 50% hard multilayer with 61 nm bilayer thickness shows the best overall wear resistance, especially at a stress of 3.65 GPa. The wear rate of our C/C multilayer (∼10−8 mm3/Nm) is 10 times lower than that of DLC coatings (∼10−7 mm3/Nm) from the current literature. The excellent wear resistance of the multilayer DLC can be explained by the combination of good toughness and the lubrication effect of the transfer layer. Such C/C multilayer structure offers an alternative to deposit DLC coatings for high stress applications without introducing other elements. [ABSTRACT FROM AUTHOR]

Highlights • The physical process of pulsed laser ablation of grinding wheel was analysed. • The equations of the plasma spatial concentration and the plasma kinetic were built. • The electronic temperature and the electron density were calculated. • The results verified the correctness and feasibility of the plasma equations. Abstract Plasma expansion is anisotropic, which necessitates new plasma expansion kinetic models to precisely describe the evolution of the processes. The physical properties of the plasma during isothermal expansion during the nanosecond laser ablation of a bronze-bonded diamond grinding wheel were demonstrated in this work. Based on the regularities of the physical distribution, three-dimensional plasma equations were established, and the equations were applied to a numerical analysis of the ablation processes. Measurements using a grating spectrometer were carried out to detect the emission spectrum of the nanosecond laser ablation of a bronze-bonded diamond grinding wheel. The splash phenomena in the laser ablation process were observed with a high-speed camera. The expansion pressure of the plasma involved was low. According to the Boltzmann plot method and the Stark broadening method, the electron temperature was calculated to be 7206 K, and the electron density ranged from 5 × 1015 to 8 × 1015 cm−3. The experimental results and numerical simulation were consistent. The distribution of the plasma expansion processes presented in this work can contribute to the investigation of plasma characteristics in future research. [ABSTRACT FROM AUTHOR]

Highlights • P–H complex has the lowest energy when H occupies the AB site. • P–H complex is most stable when P is doped within the second C layers. • P–H complex is less likely to form in (1 1 1) surface than in (0 0 1) surface. Abstract Although phosphorus is an n-type donor in diamond, H impurities can bind to and passivate P. Here, H binding to a P dopant in both diamond (0 0 1) and (1 1 1) surfaces is investigated by density functional theory. The energy calculations reveal the most stable P–H complex structures for each P-doped position. P–H binding energies are the lowest for the second P doped C layer among those for four investigated P-doped C layers. H migration from on-surface to P in the second C layer is exothermic, with an energy barrier of zero, whereas that from on-surface to P below the second C layer is endothermic, with an energy barrier greater than 0.95–7.09 eV. Thus, both of binding energy and migration calculations imply that P–H complex is more likely to form when P is doped in the second C layer than when P is doped below the second C layer. Moreover, H migration energy barrier from on-surface to P below the second C layer in the (1 1 1) surface is at least 0.85 eV greater than that in the (0 0 1) surface, which indicates that P–H complex is less likely to form in (1 1 1) surface than in (0 0 1) surface. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • N atoms can adsorb on the fully H-Ter-D (0 0 1) surface with E ad = 3.47 eV. • N atoms can adsorb on the 1ORS slab and abstract the H atom nearby. • N atoms can easily migrate along the dimer chain direction on the 2ORS-CO slab. • A deposited C atom can easily migrate in the region of a nitrogen atom adsorbed. • N atoms adsorbed can be abstracted by the other deposited N atoms. Abstract In this paper, the adsorption and migration behaviors of nitrogen (N) atoms on the hydrogen -terminated diamond (0 0 1) surface [H-Ter-D (0 0 1) surface] were investigated. The adsorption energy, the electron charge and the magnetic moment were calculated through first principles methods. The investigation results show that on the fully H-Ter-D (0 0 1) surface, all surface C atoms have saturated bonds. However, the N atom can abstract the H atom from a surface carbon atom nearby or lead to the bond breaking of the dimer carbon atoms to form bonds with the surface carbon atoms. The maximum energy of adsorption reaches to 3.47 eV, corresponding to a stable configuration structure. The charge analysis and the density of state analysis further reveal that the N atom adsorbed has unpaired electrons, which provides the opportunity for adsorption of CH radicals. On the H-Ter-D (0 0 1) surface with one open radical site (1ORS) slab, the N atom can abstract the H atom from a surface carbon atom nearby and bond with the dimer carbon atoms. The adsorption energy rises to 4.85 eV. On the H-Ter-D (0 0 1) surface with the 2ORS slab, the activation energy for a N atom to migrate along the dimer chain to the next dimer is 1.31 eV. Moreover, the adsorption of the N atom on the 1ORS surface promotes the adsorption of a C atom nearby and improves the ability of C atom migration, which is beneficial for the growth of the diamond grains. According to the charge transform analysis, the electronegativity of N atoms plays an important role in their adsorption behaviors. In addition, when the N atom has been adsorbed on the H-Ter-D (0 0 1) surface, it could still be abstracted by the other deposited N atoms; this phenomenon may be the reason for a low deposition efficiency of N atoms in the N-doped diamond films. [ABSTRACT FROM AUTHOR]

Highlights • Boron content of δ-doped diamond layers are calculated by TEM. • Howie-Whelan equation is used to relate the TEM contrast with the boron content. • An iterative procedure is used to solve Howie-Whelan equation with two variables. • Lamella thickness and boron content are calculated from TEM contrast. • TEM boron content quantification agrees with that measured by SIMS. Abstract Ultimate spatial resolution in boron δ-doped homoepitaxial diamond interfaces has been achieved by diffraction contrast technique in Transmission Electron Microscopy. The combination of two reflections with the Howie-Whelan equations allows profiling the boron content of δ-doped diamond homoepitaxial layers by fitting experimentally measured CTEM intensities with the theoretical ones. To validate the method, the obtained doping profiles are compared with that of secondary ion mass spectrometry, obtaining a boron concentration of 1.6·1021 at/cm−3, which is in good agreement with that of SIMS. This approach is capable to perform dopant concentration quantification in a non-destructive way, and provides the possibility of nanometric resolution dopant concentration mapping by TEM. [ABSTRACT FROM AUTHOR]

We report the formation of atomically flat hydroxyl-terminated (OH-terminated) diamond (1 1 1) surfaces, which are obtained by annealing hydrogen-terminated (H-terminated) surfaces in water vapor. When the annealing temperature exceeded 500 °C, the two-dimensional hole gas layers on the H-terminated surface disappeared. When Fourier transform infrared attenuated total reflectance spectroscopy was applied on the water vapor-annealed surface, a C O H peak was observed. Atomic force microscopy images showed identical surface morphology before and after water vapor annealing. [ABSTRACT FROM AUTHOR]

Fabrication of dual-termination Schottky barrier diode (SBD DT ) by using oxygen-/fluorine-terminated diamond (OT-/FT-diamond) has been carried out on P-/P+ diamond. X-ray photoelectron spectroscopy (XPS) measurement was used to determine the chemical composition of OT-/FT-diamond surface treated by ultraviolet ozone and C 4 F 8 plasma, respectively. The barrier heights of Au on OT-/FT-diamond were calculated to be 2.0 ± 0.12 and 2.39 ± 0.12 eV, respectively. Au film was patterned on the OT-/FT-diamond as the schottky electrode, and Ti/Au film were deposited on the backside of substrate as ohmic electrode, then a SBD DT was achieved completely. SBD DT exhibits better forward and reverse I-V characteristics based on the optimum OT-/FT-diamond (W O /W F ) area ratio 0.2, which illustrates that the combination of dual surface termination is an efficient way to optimize the performance of diamond SBD. [ABSTRACT FROM AUTHOR]

In this work, we used X-ray photoelectron spectroscopy to measure barrier height values for different metals (Au, Pt, Pd, Ir, Cu) on nitrogen terminated (1 0 0) diamond. Three types of diamond surface (hydrogen-, oxygen-, fluorine-terminated diamond surface) were used as the initial surfaces. Then, nitrogen terminated diamond surface was formed by reactive ion etching on the initial diamond surfaces for comparison. Thin films of Au, Pt, Pd, Ir and Cu were evaporated by electron beam to form metal/N-diamond contacts, respectively. The barrier height values for Au, Pt, Pd, Ir and Cu on nitrogen terminated (1 0 0) diamond contacts were determined to be 2.37 eV, 2.14 eV, 1.78 eV, 2.20 eV and 1.84 eV, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calculation of activation energies of acetone and methane precursors. • Decomposition paths confirmation of three liquid-doped molecules. • Growth rate comparison of diamond films fabricated using various precursors. • Distribution of doped elements detected by TOF-SIMS. Fabricating diamond films using liquid carbon source precursors in hot filament chemical vapor deposition (HFCVD) is an emerging technology. Although some experiments have demonstrated the feasibility of depositing doped diamond films using liquid carbon source precursors such as acetone, the theoretical explanation still needs to be elucidated. In this study, the density functional theory (DFT) method was used to analyze the decomposition and adsorption processes of acetone and methane on the surface of a diamond (1 1 1) models and to clarify the advantages of liquid carbon source precursors. The decomposition and adsorption reaction processes of trimethyl borate, urea, and ethyl orthosilicate on the surface of diamond (1 1 1) model were also analyzed to elucidate the doping mechanisms of B, N, and Si elements. Additionally, undoped diamond films were fabricated using acetone and methane precursors, illustrating that liquid precursors have higher growth rates than gas precursors. B-, N-, and Si-doped diamond films were also fabricated using liquid-doped carbon source precursors. Element detection by TOF-SIMS illustrates that all three elements had been doped into the diamond films and were uniformly distributed. Conversely, no doping elements were detected in N-doped diamond film fabricated with nitrogen and methane precursors. [ABSTRACT FROM AUTHOR]

In this work, Cu, Ag, or Ag/Cu was used as a metal catalyst to study the surface texturization of diamond-wire-sawn (DWS) multi-crystalline silicon (mc-Si) wafer by a metal-assisted chemical etching (MACE) method. The DWS wafer was first etched by standard HF-HNO 3 acidic etching, and it was labeled as AE-DWS wafer. The effects of ratios of Cu(NO 3 ) 2 :HF, AgNO 3 :HF, and AgNO 3 :Cu(NO 3 ) 2 on the morphology of AE-DWS wafer were investigated. After the process of MACE, the wafer was treated with a NaF/H 2 O 2 solution. In this process, H 2 O 2 etched the nanostructure, and NaF removed the oxidation layer. The Si {1 1 1} plane was revealed by etching the wafer in a mixture of 0.03 M Cu(NO 3 ) 2 and 1 M HF at 55 °C for 2.5 min. These parallel Si {1 1 1} planes replaced some parallel saw marks on the surface of AE-DWS wafers without forming a positive pyramid or an inverted pyramid structure. The main topography of the wafer is comprised of silicon nanowires grown in <1 0 0> direction when Ag or Ag/Cu was used as a metal catalyst. When silicon is etched in a mixed solution of Cu(NO 3 ) 2 , AgNO 3 , HF and H 2 O 2 at 55 °C with a concentration ratio of [Cu 2+ ]/[Ag + ] of 50 or at 65 °C with a concentration ratio of [Cu 2+ ]/[Ag + ] of 33, a quasi-inverted pyramid structure can be obtained. The reflectivity of the AE-DWS wafers treated with MACE is lower than that of the multiwire-slurry-sawn (MWSS) mc-Si wafers treated with traditional HF + HNO 3 etching. [ABSTRACT FROM AUTHOR]

Peeling is regarded as a main technique barrier for the application of coating. Many factors affects the peeling of coating. Among them, the interfacial properties between coating and substrate plays a vital role. In this work, the β -Si 3 N 4 /diamond interface is conducted as the sample to study the changes in atomic structure and potential energy in the process of detachment by the first-principles calculations. The β -Si 3 N 4 /diamond (2 × 2) crystal unit is used as the calculated model. The detachment is simulated by moving up β -Si 3 N 4 far from diamond by the 0.1 Å of each step. The results show that in the beginning of detachment, the bonds in the interface keep a constant length, rather than extension like spring. When the distance between β -Si 3 N 4 and diamond reaches a certain distance, the interfacial bonds would suddenly break, and the elongated β -Si 3 N 4 resumes its original statues indicating that the interface between two surfaces may exist a threshold value to control the peeling. When the external force is less than this threshold value, the peeling of coating would not occur. However, once the external force is greater than this one, the peeling would immediately present. The interface presents the brittle failure in the process of detachment, which is in good agreement with the experimental observation. Meanwhile, the different physical properties between van der Waals and quantum effects lead to the transient status in the process of detachment, where although the interfacial bonds are broken, the adhesive strength is still strong due to its low negative adsorption energy. [ABSTRACT FROM AUTHOR]

Phenomena related with the diamond surface of both power electronic and biosensor devices govern their global behaviour. In particular H- or O-terminations lead to wide variations in their characteristics. To study the origins of such aspects in greater depth, different methods to achieve oxygen terminated diamond were investigated following a multi-technique approach. DFT calculations were then performed to understand the different configurations between the C and O atoms. Three methods for O-terminating the diamond surface were performed: two physical methods with ozone at different pressures, and an acid chemical treatment. X-ray photoelectron spectroscopy, spectroscopic ellipsometry, HRTEM, and EELS were used to characterize the oxygenated surface. Periodic-DFT calculations were undertaken to understand the effect of the different ways in which the oxygen atoms are bonded to carbon atoms on the diamond surface. XPS results showed the presence of hydroxyl or ether groups, composed of simple C O bonds, and the acid treatment resulted in the highest amount of O on the diamond surface. In turn, ellipsometry showed that the different treatments led to the surface having different optical properties, such as a greater refraction index and extinction coefficient in the case of the sample subjected to acid treatment. TEM analysis showed that applying temperature treatment improved the distribution of the oxygen atoms at the interface and that this generates a thinner amount of oxygen at each position and higher interfacial coverage. Finally, DFT calculations showed both an increase in the number of preferential electron transport pathways when π bonds and ether groups appear in the system, and also the presence of states in the middle of the band gap when there are π bonds, C C or C O. [ABSTRACT FROM AUTHOR]

A highly oriented AlN layer has been successfully grown along the c-axis on a polycrystalline chemical vapor deposited (CVD) diamond by RF reactive magnetron sputtering. Structural, morphological and mechanical properties of the heterostructure were investigated by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Nano-indentation and Four-probe meter. A compact AlN film was demonstrated on the diamond layer, showing columnar grains and a low surface roughness of 1.4 nm. TEM results revealed a sharp AlN/diamond interface, which was characterized by the presence of a distinct 10 nm thick buffer layer resulting from the initial AlN growth stage. The FWHM of AlN (002) diffraction peak and its rocking curve are as low as 0.41° and 3.35° respectively, indicating a highly preferred orientation along the c-axis. AlN sputtered films deposited on glass substrates show a higher bulk resistivity (up to 3 × 10 12 Ω cm), compared to AlN films deposited on diamond (∼10 10 Ω cm). Finally, the film hardness and Young’s modulus of AlN films on diamond are 25.8 GPa and 489.5 GPa, respectively. [ABSTRACT FROM AUTHOR]

The surface morphology of (111) diamond after hydrogen plasma treatment was studied in detail by atomic force microscopy. As a result, we clearly showed that the hydrogen plasma treatment formed atomically flat diamond (111) surfaces due to its anisotropic etching. Elucidation of the diamond etching mechanism by hydrogen plasma is important for understanding and controlling diamond growth via plasma-enhanced chemical vapor deposition. In this study, we discussed the origin of anisotropic etching by hydrogen plasma. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diamond films were deposited on refractory high entropy alloys by MPCVD. • Continuous diamond film was obtained within 30 min. • Diamond was grew on mixed-carbides layer with an orientation of Dia. [0 1 1] //XC [0 0 1]. • The corrosion of specimens has been improved, and corrosion potential is up to −0.02 V/SCE. • The high nucleation density attributed to the solubility and relative nucleation energy barrier. Growing diamond has been a long-standing challenge. It is found the diamond grows on refractory metals (such as Zr, Hf, Ti) hardly to form a continuous film with a high nucleation density because of diffusion of carbon. In this study, we reported an approach to grow diamond on high entropy alloys (HEAs) of TiZrHfTaMo, TiZrHfNbMo, TiHfNbTaMo as substrates by chemical vapour deposition. Diamond films with a nucleation density as much as 108 ∼ 1010 site/cm2 grow on the mixed-carbides XC (X = Hf, Zr and Ta etc.) layer, which is 2 ∼ 3 orders of constituent metals. The orientation relationship is identified as diamond[0 1 1] // XC[0 0 1] with XC mixed-carbides by high resolution transmission electron microscope. The continuous diamond films can be obtained within 30 min. The high nucleation density and rapid growth on HEAs refer to solubility of carbon and relative nucleation energy barrier. Moreover, the corrosion of current specimens in 3.5 wt% NaCl solution have been improved (e.g., corrosion potential value is as much as −0.02 V/SCE) because of the continuous diamond film. Current result facilitates promising industrial applications of HEAs and diamonds by combining the advantages of them. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel method for diamond surface hydroxylation was developed. • The OH-diamond shows high intensity of C O bonds and untraceable C O bonds. • O H and C O stretching vibration was observed in the FTIR spectra. • APTES was successfully functionalized on the OH-diamond surface. • The stability of OH-diamond was investigated by ReaxFF and DFT calculations. Functionalized diamond is promising for biosensing applications due to its attractive properties. Hydroxyl terminated diamond (OH-diamond) surface with chemically functionalizable carboxyl groups is beneficial to silanization, which creating an amine termination is necessary to immobilize proteins and DNA. However, fabrication of high quality OH-diamond surface is still difficult. In this work, OH-diamond is obtained by hydroxide ion treatments in deionized water at high voltages up to 3000 V. The OH-diamond exhibited high intensity of singly oxidized C Ⅰ carbon bonds (C OH and C O C) and untraceable doubly oxidized C Ⅱ carbon bonds (C O or O C O), characterized by X-ray photoelectron spectroscopy measurements. Meanwhile, O H and C O stretching vibration was observed in the Fourier transform infrared spectra. Furthermore, silanizaiton is achieved by 3-aminopropyltriethoxysilane (APTES) on the OH-diamond surface via condensation reaction with surface C OH groups. In the end, the stability of OH-diamond surface was investigated by ReaxFF simulations and density function theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Twins enhance the plasticity of diamond and relieve the stress concentration. • Twins lead to change of the distribution and type of dislocation. • The damage of nanotwinned diamond is caused by amorphization and detwinning. Nanotwinned diamond is a promising candidate material for cutting tools, high-pressure physics, and other fields due to its excellent properties of much higher hardness and toughness as compared to single-crystal diamond. Remarkable achievements have been achieved in understanding the mechanical properties and deformation mechanism when nanotwinned diamonds are subject to compression, fracture, or indentation. In this work, the response of nanotwinned diamonds under scratching was studied using molecular dynamics simulation. The morphology of chips and subsurface damage, the distribution of temperature and stress, the formation process of subsurface damage, and the plastic deformation mechanism were systematically investigated. Compared with single-crystal diamonds, more obvious plastic deformation was found in nanotwinned diamonds. Unlike single crystal diamonds, in which perfect dislocations mainly slipped on those {1 1 1} planes inclined to the scratching direction, for the nanotwinned diamond, partial dislocation was found to be the dominant dislocation type and only slipped on the {1 1 1} planes parallel to the twin boundaries. Furthermore, detwinning was also observed during subsurface damage formation besides amorphism. These results show the mechanical response of nanotwinned diamonds under scratching and provide theoretical guidance for the application of nanotwinned diamonds. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermal transport simulation of AlN/diamond nanostructured heterostructure was performed by molecular dynamics. • The AlN/diamond nanostructured interface can achieve a 28% reduction in TBR compared to the planar interface. • The effect of nanopillar height on the thermal boundary resistance of the AlN/diamond interface was analyzed. • Relationship between the VDOS at the AlN/diamond interface and thermal transport performance was clarified. Interfacial thermal transport has become a significant bottleneck in thermal management, particularly for the electronic high-power devices represented by III-V semiconductor devices. Diamond has great potential to be integrated with devices to dissipate heat efficiently due to its ultra-high thermal conductivity. In this paper, the Non-equilibrium Molecular Dynamics method, taking into consideration of the parameters such as the type of the interleaved nanopillars, the size and the height of the nanopillars, was used to study the influence of nanopillars on the thermal boundary resistance (TBR) at AlN/diamond interfaces. The TBR of the optimal AlN/diamond interface of nanopillar structures could be reduced by 28% compared to the planar interface. The vibrational density of states (VDOS) analysis of both AlN and diamond on each side of the interface can reveal that the enhancement of AlN intermediate frequency phonons and the shift of diamond VDOS towards the lower frequency can contribute to the optimization of the interfacial thermal transport. Hence, this work can provide a deeper understanding of the impact of nanostructures on the interfacial thermal transport and can also be a guideline for efficient thermal management through the introduction of nanostructures at the heterogeneous interfaces. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability. • Ar thermal desorption occurs via diffusion between local defects, greatly enhanced between 600 and 700 °C. • Implantation at 400 °C results in two distinct regions: graphitic and diamond. • Retained amount of Ar upon 700 eV implantation at RT is about 100 times lower than that upon 5000 eV. • Ar entrapped in a high crystalline diamond matrix is under higher compressive stress than in graphitic/amorphous carbon. The retention and thermal stability of Ar implanted into polycrystalline diamond surfaces with 700 and 5000 eV Ar ions, with high dose (HD) and low dose (LD) of 1016 and 1014 ions/cm2 at room temperature (RT) and 400 °C were investigated. Upon implantation at 400 °C, the thermal stability of the retained Ar is very high and can exceed 1000 °C, whereas, upon RT implantation at the same energy, it is below ∼800 °C. Ar entrapped in a local high crystalline diamond environment possesses a very high thermal stability compared to when it is entrapped in a graphite/amorphous local carbon environment. Ar thermal desorption occurs via diffusion between local defects, greatly enhanced between 600 and 700 °C. Implantation at 400 °C (at HD) results in two distinct regions: graphitic and highly crystalline diamond with low defect density due to dynamic annealing and direct desorption of Ar entrapped within the graphitic/damaged region during the implantation. Ar entrapped in a high crystalline diamond matrix is under higher compressive stress than in graphitic/amorphous carbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stability of metals and diamond interface supercells are evaluated through the calculation of binding energy. • Reliable interfacial atomic models and detailed interface electronic structures are provided. • Potential application of each metal as an electrode was evaluated by Schottky barrier heights. Diamond electronic devices have attracted great attention in the field of high power and high frequency applications due to their excellent properties. For diamond electronics, metal and diamond contacts are important for the electronic device performance, with Schottky barrier heights (SBHs) playing a crucial role in the transmission properties of diamond devices. To make sense of their electrical characteristics, the interface supercells of diamond (1 1 1) with diverse metals have been explored using first-principles calculations. Clear metal-induced gap states (MIGS) can be observed at the interface, resulting in an enhanced Fermi-level pinning effect, with a pinning factor of 0.3. The results surprisingly show that there is a larger transverse tunneling probability and a smaller longitudinal tunneling probability for all diamond contact interfaces. All interfaces studied are p-type contacts with the metal Fermi level close to the diamond valance band edge. The low work function metals such as Sc and Ti are excellent at generating Schottky contacts with relatively higher SBHs (∼1.0 eV ± 0.6 eV). Pt and Ni have a smallest barrier height of ∼ 0.5 eV, making them ideal for ohmic electrodes with low contact resistance. The calculated SBHs are within the range of the experimental findings. This work gives insight into the electrical structural changes at the contact interface between metal and diamond, which provides a theoretical basis for selecting suitable electrodes for high-power diamond devices. [ABSTRACT FROM AUTHOR]

Nowadays the availability of very thin diamond layers in the range of nanometers as well as the possibility to characterize such delta-layer structures are required for the field of photonics and spintronics, but also for the development of next generation high power devices involving boron doping. The fabrication of diamond structures with abrupt interfaces such as superlattices and quantum wells has been recently improved. A very accurate characterization is then essential even though the analysis of such structures is arduous and challenging. SIMS analyses are commonly used to obtain depth profiles of dopants. However, below 10 nm in thickness, SIMS induced ion mixing effects which are no longer negligible. Then the raw SIMS profile might differ from the real dopant profile. In this study, we have analyzed a diamond structure containing a thin boron epilayer, especially synthesized to achieve SIMS analysis on both sides and to overcome the effects of ion mixing. We evidence the ion mixing induced by primary ions. Such a structure is a delta diamond layer, comparable to classical boron-doped delta-layer in silicon. Our results show that the growth of boron-doped delta-layer in diamond is now well controlled in terms of thickness and interfaces. [ABSTRACT FROM AUTHOR]

Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu2O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu2O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu2O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu2O/BDD showed a much higher current density (-0.33 mA/cm2) and photoconversion efficiency (0.28%) compared to the unmodified Cu2O/BDD electrode, which are only -0.12 mA/cm2 and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu2O surface is a crucial parameter in this regard. [ABSTRACT FROM AUTHOR]

Mo 2 C submicron layer coated diamond particles prepared by a molten salts route with Mo powder as the starting material were used as the filler in Cu- and Al- matrix composites. The microstructure and thermal property of the composites prepared by a vacuum pressure infiltration method were investigated. When introducing a 500 nm thick Mo 2 C layer, the thermal conductivity of the composites with different matrix presented different performance. A high thermal conductivity (657 W m −1 K −1 ) was obtained in diamond/Cu composites owing to the improved interfacial bonding and lower interfacial thermal resistance, while the thermal conductivity of diamond/Al composites decreased from 553 W m −1 K −1 to 218 W m −1 K −1 when introducing the Mo 2 C layer, which can be attributed to the formation of harmful granule-phase (Al 12 Mo) at the interface of diamond and aluminum. This work provides a promising approach to improve performance of diamond reinforced metal matrix composites by selecting carbide as an interface modifier. [ABSTRACT FROM AUTHOR]

[Display omitted] • The initial reason for Fe-induced graphitization on the diamond (1 1 0) surface was elucidated by the first-principles calculation. • The charge transfer of Fe adatoms reduces the potential energy barrier between diamond and graphite. • The Fe adatom can weaken interlayer C C bonds and change the dissociation direction of the diamond (1 1 0) surface. Understanding the diamond graphitization mechanism is an essential subject in manufacturing research since it helps elucidate the reason for the material removal. Our work addressed the mechanism of Fe-induced graphitization of diamond (1 1 0) surfaces (Dia-(1 1 0)-Surf) by first-principles calculations. The results pointed out that Fe atoms adsorbed at hollow sites could acquire the most stable configuration on the Dia-(1 1 0)-Surf. Meanwhile, the Fe adatom could change interlayer binding energies of C C bonds of various layered. As the amount of Fe atoms increased, the weakening/enhancement effect of C C bonds tended to be apparent. Interestingly, Fe adatoms not only changed interlayer binding energies of C C nearby but also affected the dissociation direction of the surface microstructure. The weakened C C bonds could provoke the flattening of the sixfold chair ring structure of C atoms. The extension direction of the sixfold chair ring structure changed from horizontal to oblique, resulting in eliminating lateral compressive stress. It might be the origin of the Fe-induced graphitization of Dia-(1 1 0)- Surf. Moreover, the migration behaviors of the Fe atom have been studied. It could be inferred that the migration activation energy and movement direction of Fe adatoms were associated with the material removal rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calculation of doping energies of different co-doped diamond models. • Absorption position confirmation of O atoms by binding energies results. • Comparison of activation energies of O 2 molecules on diamond surfaces. • High-temperature oxidation resistance experiment of different diamond films. The oxidation resistance of diamond films is essential in maintaining their good performance in high-temperature applications. Although numerous experiments have proved that doping can improve diamond films' oxidation resistance properties, the theoretical explanation still needs to be discussed. In this study, the density functional theory (DFT) method is used to elucidate the influence mechanism of multiple doping, including B, N, and Si elements doping, on the oxidation resistance of diamond films and obtain the doped diamond films with the optimal oxidation resistance. These include the confirmation of the different doped diamond (1 1 1) models, the adsorption site of the O atoms on the various doped diamond surfaces, and the subsequent reaction process of O 2 molecules with the C atom. The results show that the multi-doped diamond model has the most considerable activation energy due to the synergistic effect of the three elements, which represents better oxidation resistance properties. In addition, eight kinds of diamond films are fabricated on the silicon substrate. Their weight loss at high temperatures is conducted to evaluate oxidation resistance, indicating that multiple doping can effectively reduce the high-temperature oxidation rate of diamond films, and the experimental results are consistent with the theoretical calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using microwave plasma chemical vapor deposition (MPCVD) and low-density crystal planting process to grow diamond single crystal particles with flat crystal surfaces. • The diameter and spacing of the nano-pillar etching mask were controlled by the cyclic dewetting process of copper film on the surface of diamond for the first time. • The prepared single crystal diamond nanopillars have a uniform diameter and dense arrangement, which can enhance the luminescence of diamond color centers. Diamond nanopillars can effectively improve the spontaneous emission efficiency and coupling-out efficiency of diamond-color-center single-photon sources. In this paper, a low-cost and controllable method for preparing diamond nanopillar clusters is proposed. By choosing the crystal planting method and adjusting the methane concentration of the grown diamonds, isolated single-crystal diamond particles with a flat surface were prepared. Etching masks with individually controllable diameters and spacings were prepared through the cyclic deposition and dewetting of metal films on the surface of microcrystalline diamond particles. Using inductively coupled reactive ion etching technology, diamond nanopillar clusters were prepared through oxygen plasma etching. The nanopillars were uniform in diameter and densely arranged. The single-crystal properties of the diamond nanopillars and their enhancement effect on the photoluminescence of diamond color centers were confirmed through the analysis of Raman and photoluminescence spectra. The results provide a foundation for the deviceization of diamond-color-center single-photon sources. [ABSTRACT FROM AUTHOR]

In this paper, boron doped diamond (BDD) with different thickness were prepared by hot filament chemical vapor deposition. The performance of BDD electrodes for detecting dopamine (DA) and ascorbic acid (AA) were investigated. Scanning electron microscopy and Raman spectra reveal the grain size increases and the film quality improves with the increase of film thickness. Electrochemical test show that the transfer coefficient in [Fe 3 (CN) 6 ] 3−/4− redox system increases with the increase of the film thickness. The results of selectivity and sensitivity for DA mixed with AA detection show that 8h-BDD and 12h-BDD electrodes possess well selective separated oxidation peaks of DA and AA, and the 12h-BDD electrode exhibits optimal sensitivity until the DA concentration drops to 1 μ M. [ABSTRACT FROM AUTHOR]