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The ferromagnetic (FM)/MgO structure multilayers with perpendicular magnetic anisotropy (PMA) play a crucial role in magnetic random-access memory. It is essential to explore the methods for modulating magnetic anisotropy and to clarify the underlying mechanisms. We study the regulation of the magnetic anisotropy with nitrogen (N) doping concentration (CN) in two samples: Ta/CoFe(N)/MgO/Ta (S1) and Ta/MgO/CoFe(N)/Ta (S2) with different deposition sequences. The S1 sample exhibits in-plane magnetic anisotropy (IMA) without N doping. And the sample presents PMA when CN = 15%. The S2 sample shows weak PMA without N doping, and the sample converts to IMA when CN = 15%. X-ray photoelectron spectroscopy is performed to evaluate the oxidation level of Fe at the CoFe/MgO interface by the peak area ratio of Fe oxide to Fe (ϵ). It is believed that excessively high and low ϵ values correspond to over-oxidation and under-oxidation of Fe, respectively. For films deposited in different sequences, both over-oxidation and under-oxidation lead to IMA, while moderate oxidation facilitates the formation of PMA. The microstructure analysis reveals that the N doping does not affect the crystallization of the films, indicating that magnetocrystalline anisotropy has a minor influence on the changes of K eff. [ABSTRACT FROM AUTHOR]

Glow discharges are known to be limited for running at high current densities (typically below 0.1 A ⋅ c m − 2 ). Magnetically enhanced plasmas overcome this limitation, reaching up to two orders of magnitude higher current densities. However, the highest reported discharge current density hardly reaches 10 A ⋅ c m − 2 even in high power impulse magnetron sputtering (HiPIMS). Here, we report on the long (∼1 ms) pulsed operation of the magnetron in helium with an over-dense current (∼30 A ⋅ c m − 2 , usual for arcs) while preserving the glow mode. This regime defying the arcs was called hyper power impulse magnetron (HyPIM) because the power injected per pulse is several times higher than in HiPIMS for the same average power and pulse duration. HyPIM operation mode is distinguished from HiPIMS by the limited pulse voltage and is unsuitable for thin film deposition but may interest plasma switches. These huge currents were obtained for two cathode materials, molybdenum (Mo) and tungsten (W). Different experimental diagnostics bring insights into the physical phenomena governing the HyPIM plasma. A discussion on the role played by the metal atoms on the current unveils the origin of such exceptional glow current all along the pulse and the key role of the helium metastable atoms. A schematic of the kinetic steps of the HyPIM discharge is proposed. [ABSTRACT FROM AUTHOR]

In this perspective we discuss the progress made in the mechanistic studies of the surface chemistry associated with the atomic layer deposition (ALD) of metal films and the usefulness of that knowledge for the optimization of existing film growth processes and for the design of new ones. Our focus is on the deposition of late transition metals. We start by introducing some of the main surface-sensitive techniques and approaches used in this research. We comment on the general nature of the metallorganic complexes used as precursors for these depositions, and the uniqueness that solid surfaces and the absence of liquid solvents bring to the ALD chemistry and differentiate it from what is known from metalorganic chemistry in solution. We then delve into the adsorption and thermal chemistry of those precursors, highlighting the complex and stepwise nature of the decomposition of the organic ligands that usually ensued upon their thermal activation. We discuss the criteria relevant for the selection of co-reactants to be used on the second half of the ALD cycle, with emphasis on the redox chemistry often associated with the growth of metallic films starting from complexes with metal cations. Additional considerations include the nature of the substrate and the final structural and chemical properties of the growing films, which we indicate rarely retain the homogeneous 2D structure often aimed for. We end with some general conclusions and personal thoughts about the future of this field. [ABSTRACT FROM AUTHOR]

Cadmium selenide (CdSe) quantum dots (QDs) with different size, 2.5 and 3.2 nm, were successfully deposited on mesoporous titanium dioxide (TiO2) (Degussa-P25) nanostructures by electrophoretic deposition method (EPD) at the applied voltage 100 V for 120 s deposition time. In this study, the morphology of CdSe films deposited by EPD and the performance of the film when assembled into a solar cell were investigated. From the field emission scanning electron microscopy cross-section, the thickness of the CdSe nanoparticles with size 2.5 nm films were 3.4 and 3.0 μ m for CdSe 3.2 nm nanoparticles film. The structure of 2.5 nm is denser than compare of 3.2 nm CdSe nanoparticles. From UV visible spectroscopy, the band gap calculated for 2.5 nm CdSe nanoparticles is 2.28 eV and for 3.2 nm is 2.12 eV. Photovoltaic characterization was performed under an illumination of 100 mW cm−2. A photovoltaic conversion efficiency of 1.81% was obtained for 2.5 nm CdSe and 2.1% was obtained for 3.2 nm CdSe nanoparticles. This result shows that the photovoltaic efficiency is dependent on CdSe nanoparticle size. [ABSTRACT FROM AUTHOR]

SPPARKS is an open-source parallel simulation code for developing and running various kinds of on-lattice Monte Carlo models at the atomic or meso scales. It can be used to study the properties of solid-state materials as well as model their dynamic evolution during processing. The modular nature of the code allows new models and diagnostic computations to be added without modification to its core functionality, including its parallel algorithms. A variety of models for microstructural evolution (grain growth), solid-state diffusion, thin film deposition, and additive manufacturing (AM) processes are included in the code. SPPARKS can also be used to implement grid-based algorithms such as phase field or cellular automata models, to run either in tandem with a Monte Carlo method or independently. For very large systems such as AM applications, the Stitch I/O library is included, which enables only a small portion of a huge system to be resident in memory. In this paper we describe SPPARKS and its parallel algorithms and performance, explain how new Monte Carlo models can be added, and highlight a variety of applications which have been developed within the code. [ABSTRACT FROM AUTHOR]

Understanding and modeling plasma–surface interactions frame a multi-scale as well as multi-physics problem. Scale-bridging machine learning surface surrogate models have been demonstrated to perceive the fundamental atomic fidelity for the physical vapor deposition of pure metals. However, the immense computational cost of the data-generating simulations render a practical application with predictions on relevant timescales impracticable. This issue is resolved in this work for the sputter deposition of AlN in Ar/N2 discharges by developing a scheme that populates the parameter spaces effectively. Hybrid reactive molecular dynamics/time-stamped force-bias Monte Carlo simulations of randomized plasma-surface interactions/diffusion processes are used to setup a physics-separating artificial neural network. The application of this generic machine learning model to a specific experimental reference case study enables the systematic analysis of the particle flux emission as well as underlying system state (e.g. composition, density, point defect structure) evolution within process times of up to 45 min. [ABSTRACT FROM AUTHOR]

High-resolution, x-ray phase contrast microscopy, a key technique with promising potential in biomedical imaging and diagnostics, is based on narrow-slit high-aspect-ratio gold gratings. We present the development, fabrication details, and experimental testing of the freestanding 10 ÎĽ m thick gold membrane masks with an array of 0.9â€"1.5 ÎĽ m void slit apertures for a novel low-energy x-ray microscope. The overall mask size is 4 mm Ă— 4 mm, with a grating pitch of 7.5 ÎĽ m, 6.0â€"6.6 ÎĽ m wide gold bars are supported by 3 ÎĽ m wide crosslinks at 400 ÎĽ m intervals. The fabrication process is based on gold electroplating into a silicon mold coated with various thin films to form a voltage barrier, plating base, and sacrificial layer, followed by the mold removal to obtain the freestanding gold membrane with void slit apertures. We discuss key aspects for the materials and processes, including gold structures homogeneity, residual stresses, and prevention of collapsing of the grid elements. We further demonstrate the possibility to obtain high-resolution, high contrast 2D images of biological samples using an incoherent, rotating anode x-ray tube. [ABSTRACT FROM AUTHOR]

Humidity monitoring is essential for food processing, pharmaceutical, and precision electronics industries. Conventional humidity sensors based on metal oxides and ceramics show an ideal response to variation humidity. However, long response time and complex manufacturing processes pose a challenge for their more comprehensive application and further development. Resistive polymers show promise in antistatic materials and sensor applications. In this study, gelatin composite, a popular water-soluble polymer, is mixed with carbon black nanoparticles for better humidity sensitivity. Using the state-of-the-art thin film deposition method, the designed interdigitated electrode is covered by a nano-scale thin film of the prepared composite film. The relative humidity (RH) range between 20.3% and 83.2% can be well detected according to the evaluation of a customized chemical vapors measurement system. Furthermore, an extreme linear relation and high sensitivity of 0.35 mV/%RH are achieved for the range from the RH of 20%â€"65.2%. Highly repeatable performance can be demonstrated by repeated experiments with several humidities. Rapid response and recovery features are found during the characterization, while the response and recovery time are lower than 10 s. [ABSTRACT FROM AUTHOR]

Two classic radio-frequency (RF) plasmas, i.e., the capacitively and the inductively coupled plasmas (CCP and ICP), are widely employed in material processing, e.g., etching and thin film deposition, etc. Since RF plasmas are usually operated in particular circumstances, e.g., low pressures (mTorrâ€"Torr), high-frequency electric field (13.56 MHzâ€"200 MHz), reactive feedstock gases, diverse reactor configurations, etc., a variety of physical phenomena, e.g., electron resonance heating, discharge mode transitions, striated structures, standing wave effects, etc., arise. These physical effects could significantly influence plasma-based material processing. Therefore, understanding the fundamental processes of RF plasma is not only of fundamental interest, but also of practical significance for the improvement of the performance of the plasma sources. In this article, we review the major progresses that have been achieved in the fundamental study on the RF plasmas, and the topics include 1) electron heating mechanism, 2) plasma operation mode, 3) pulse modulated plasma, and 4) electromagnetic effects. These topics cover the typical issues in RF plasma field, ranging from fundamental to application. [ABSTRACT FROM AUTHOR]

Cu/Cu2O composite thin films were prepared by pulsed electrodeposition in a single electrolyte solution. The microstructure and performance of the composite thin films were tested and analysed. The photocatalytic performance of Cu/Cu2O composite thin films for methylene blue was studied. The results showed that the prepared Cu/Cu2O was a triangular pyramid with a (111) plane preferential orientation, the grain size was approximately 500–1000 nm, and the band gap width was wider than that of pure Cu2O. The carrier concentration, photocurrent and open-circuit voltage of Cu/Cu2O increased, and the alternating current impedance obviously decreased. Compared with pure Cu2O, Cu/Cu2O with a pulse time of 85–5 s had good photocatalytic performance. The recombination of Cu allows the photogenerated electrons on the Cu2O conduction band to be quickly transferred to the Cu surface, which promotes the effective separation of photogenerated charge on the Cu2O surface. After the stability test, the degradation rate of methylene blue was almost unchanged after 5 cycles. Methylene blue degradation process studies have shown that active hydroxyl free radicals and holes play a main role. Twelve types of degradation of intermediate products were determined, and the possible paths of MB degradation were proposed. The research results could be used to provide a new way of thinking for the treatment of refractory organic compounds in water environments. [ABSTRACT FROM AUTHOR]

A small-volume hot-wall batch reactor with excess precursor loading was proposed for supercritical fluid deposition of Cu during the fabrication of sub-millimeter-scale, metal-coated terahertz (THz) wave devices. Conformal film formation was experimentally demonstrated, validating our method. Our method enables a much higher precursor concentration (at least 20 mol mâˆ'3) than the conventional method (below 2 mol mâˆ'3), facilitating conformal film formation on sub-millimeter structures. Kinetic analysis revealed that our proposed method was applicable for fabricating rectangular metal-coated THz waveguides; furthermore, it was promising for monolithically integrated THz wave devices. [ABSTRACT FROM AUTHOR]

Effect of radio frequency (RF) power on aluminum nitride (AlN) film crystallinity has been studied under low gas pressure of ≥ 0.1 Pa and low RF power of ≥ 3 W with Ar-20%N2 gas by a proposed balanced magnetron cathode with a high plasma production efficiency. The gas pressure and the RF power dependences of AlN film crystallinity show that the c -axis oriented AlN films can be obtained only at 50 W and 100 W in 0.1 Pa. The AlN film crystallinity was not promoted in the low RF power range of <50 W. An Ar-rich sputtering condition at 0.1 Pa induced the Alâ€"Al bonds in the deposited films in a high RF power range of ≥ 15 W. The control of the total flux balance between Al and nitrogen atoms at the substrate surface is important to design the optimum sputtering condition at 0.1 Pa. [ABSTRACT FROM AUTHOR]

We demonstrate a bottom-up process for programming the deposition of coaxial thin films aligned to the underlying dopant profile of semiconductor nanowires. Our process synergistically combines three distinct methodsâ€"vaporâ€"liquidâ€"solid nanowire growth, selective coaxial lithography via etching of surfaces (SCALES), and area-selective atomic layer deposition (AS-ALD)â€"into a cohesive whole. Here, we study ZrO2 on Si nanowires as a model system. Si nanowires are first grown with an axially modulated n-Si/i-Si dopant profile. SCALES then yields coaxial poly(methyl methacrylate) (PMMA) masks on the n-Si regions. Subsequent AS-ALD of ZrO2 occurs on the exposed i-Si regions and not on those masked by PMMA. We show the spatial relationship between nanowire dopant profile, PMMA masks, and ZrO2 films, confirming the programmability of the process. The nanoscale resolution of our process coupled with the plethora of available AS-ALD chemistries promises a range of future opportunities to generate structurally complex nanoscale materials and electronic devices using entirely bottom-up methods. [ABSTRACT FROM AUTHOR]

Graphitic nanoplatelets (GNPs) have been treated using an ultrasonicated ozonolysis procedure to produce stable aqueous dispersions that facilitate deposition of thin films using electrophoretic deposition. The thin GNP films were then coated with zero valence (ZV) iron nanocubes using a pulsed electrodeposition technique. Characterization of the ZV-iron coating with deposition time revealed that the changing magnetic character of the ferromagnetic-graphitic hybrid material was related to the nucleation density and growth of the ZV-iron nanocubes. Density functional theory calculations show a preference for ZV-iron adsorption at the oxygen sites of the GNPs, with ZV-iron displacement of oxygen groups favored in some configurations. Transmission electron microscopy studies confirm ZV-iron growth nucleates preferentially at the graphite nanoplatelet edges and the hybrid material magnetism is affected by the convergent crystalline grain boundaries formed between adjacent ZV-iron nanocubes. [ABSTRACT FROM AUTHOR]

A discharge plasma is created by simultaneously biasing two concentric spherical grids with axisymmetric orifices. In this geometry, space charge structures in the form of multiple quasi-spherical luminous plasma bodies appear simultaneously inside and around the cathodes. The plasma formations are highly interdependent supplying each other with the particle flow and current closure necessary for the maintenance of the discharge. To diagnose these structures, space-resolved cold Langmuir probe measurements and optical emission spectroscopy investigations were performed in the axial direction allowing for the mapping of the axial profiles of plasma potential, electron temperature and density, ion density and optical emission. The existence of an accelerating double layer in the vicinity of the holes has been confirmed here, and in previous research (Teodorescu-Soare C T et al 2016 Phys. Scr. 91 034002; Schrittwieser R W et al 2017 Phys. Scr. 92 044001; Teodorescu-Soare C T et al 2019 Int. J. Mass Spectrom. 436 83). Besides the assessment of the relationship between discharge conditions and plasma parameters in the novel cathode system, the importance of a multiple concentric cathode discharge configuration is revealed for deposition applications. [ABSTRACT FROM AUTHOR]

While wet pattern transferring of polymers is faster than dry processing, it can lead to excessive undercut that will erode and distort features in patterned sacrificial regions during micro electro mechanical systems (MEMSs) fabrication. Dry etching processes based on O2, CF4 and N2 chemistry reduce undercutting of features to around 2 µm, but the resulting sidewall profiles of the patterned polymer islands are generally unsuitable for subsequent conformal deposition of thin films for surface micromachined MEMS fabrication. This paper presents a dry etching process for Prolift-100-16 polymer sacrificial layers, that employs a combination of a hard mask and a subsidiary sacrificial layer, that overcomes the limitations of undercut control and conformal deposition of physical vapour deposition techniques. The dry etching process is optimized to reduce the feature undercut to as low as 1 µm, while also producing sidewall profiles suitable for subsequent conformal deposition of thin films. [ABSTRACT FROM AUTHOR]

A 1D fluid model including a detailed chemistry for silane-hydrogen discharges as well as surface reactions to account for deposition and etching processes has been implemented to study the effects of gas pressure (1 to 3.5 Torr) and silane concentration (2 to 10%) on the deposition rate of silicon thin films in a standard RF-PECVD reactor. The thickness of the films and their deposition rate as functions of the process conditions were determined from optical modelling of UV-visible spectroscopic ellipsometry measurements. The experimental values of the deposition rate were compared with results from the 1D fluid model. SiH3 radicals are found to be the main contributor to the computed deposition rates, while H3+ ions play the main role in the etching process. The study reveals that etching by hydrogen ions must be taken into account to reproduce properly the experimental deposition rate. In particular etching by H3+ ions must be taken into account to achieve a good agreement between the experimental and modelled values of the deposition rate as a function of the total gas pressure and the silane fraction in the discharge. [ABSTRACT FROM AUTHOR]

The optical characteristics of a planar thin film waveguide system composed of air–graphene–LiNbO3 have been investigated. Monolayer or bilayer graphene of high quality are characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The refractivity and reflectivity of the air–graphene–LiNbO3 system are measured experimentally and compared with those of a LiNbO3 waveguide by the prism coupling method. The reflectivity shows an overall decrease due to the lower transmittance for graphene on the LiNbO3 substrate. The refractivity increases significantly at the wavelength of 1540 nm, which may be attributed to the generation of graphene surface plasmons excited by infrared radiation. A shaped air–graphene–LiNbO3 waveguide is designed and simulated by Mode Solutions. The distribution of an optical field is performed and analyzed. The preparation of the proposed air–graphene–LiNbO3 structure incorporates the commonly used chemical vapor deposition and thin film transfer techniques, and is compatible with existing optoelectronic integration processes, which can be employed for building various optical integrated devices. [ABSTRACT FROM AUTHOR]

Understanding the effects of thin film electroless deposition parameters at nanoscale is crucial for complete understanding and control of the thin film deposition process. In this study, we investigated and optimized the effect of PdCl2 precursor concentration on the nanoscale surface morphology of electroless deposited Pd thin film. The FESEM characterization of plain substrates showed that the dominant features of plain alumina substrates were terraces, steps and bumpy microstructures and the final surface morphologies of the deposited Pd thin film was strongly dependant on the surface morphologies of the substrate. FESEM characterization results of seeding technique displayed a thin film of Pd nanoparticles on the surface of the alumina substrate. The number of times that the seeding process was carried out was optimized at five seeding times using hydrazine as a reducing agent. FESEM characterization revealed that the nanoscale surface morphology of the Pd thin film was strongly dependent on PdCl2 precursor concentration. Three types of secondary nanoscale surface morphologies formed were nanorods, nanoflakes and flowerlike Pd nanostructures at various concentrations. The nanoflake surface density was strongly dependent on PdCl2 precursor concentration. Results of this research provided a foundation and method to tailor the nanoscale surface morphology to the specific requirement of surface dependent processes or reactions. [ABSTRACT FROM AUTHOR]

This work reports the design, manufacturing and numerical simulation approach of a 6-pixel (4.5 mm2/pixel) electroluminescent quantum dot light emitting device (QLED) based on CuInS2/ZnS quantum dots as an active layer. The QLED device was fabricated using a conventional multi-layer thin film deposition. In addition, the electrical I–V curves were measured for each pixel independently, observing how the fabrication process and layer thickness have an influence in the shape of the plot. This experimental device, enabled us to create a computational model for the QLED based on the Transfer Hamiltonian approach to calculate the current density J (mA cm−2), the band diagram of the system, and the accumulated charge distribution. Besides, it is worth highlighting that the simulator allows the possibility to study the influence of different parameters of the QLED structure like the junction capacitance between the distinct multilayer set. Specifically, we found that the Anode-HIL interface capacitance has a greater influence in the I–V curve. This junction capacitance plays an important role in the current density increase and the QLED turn-on value when a forward voltage is applied to the device. The simulation enabled that influence could be controlled by the selection of the optimal thickness and transport layers during the experimental fabrication process. This work is remarkable since it achieves to fit simulation and experiment results in an accurate way for electroluminescent QLED devices; particularly the simulation of the device current, which is critical when designing the automotive electronics to control these new nanotechnology lighting devices in the future. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of molybdenum nitride (MoN) thin film deposition using direct current reactive magnetron sputtering. We have investigated the effect of various deposition conditions on the superconducting and electrical properties of the films. Furthermore, we have shown that meander-shaped single-photon detectors made from 5 nm MoN films have saturated quantum detection efficiency at the telecom wavelength of 1550 nm. Our results indicate that MoN may be a material of interest for practical applications of low-temperature superconductors, including single-photon detectors and transition-edge sensors. [ABSTRACT FROM AUTHOR]

Solution-processed photodetectors have emerged as the next generation of sensing technology owing to their ease of integration with electron devices and of tuning photodetector performance. Currently, novel self-powered photodetectors without an external power source, for use in sensing, imaging and communication, are in high demand. Herein, we successfully developed a self-powered photodetector based on a novel solution-processed p-NiO/n-CdS:Al heterojunction, which shows an excellent current rectification characteristic ratio of up to three orders in the dark and distinctive photovoltaic behavior under light illumination. The complete solution synthesis route followed the development of CdS:Al thin films on ITO substrates by chemical bath deposition and NiO thin films by the sol-gel route. Optical absorption data revealed that NiO is more active in the UV region and CdS:Al has a majority of absorption in the visible region; so, upon light illumination, the effective separation of photogenerated carriers produces fast photodetection in the UV–visible region. The photoresponsivity values of the fabricated device were calculated to be 55 mA W−1 and 30 mA W−1 for UV and visible illumination, respectively. Also, the device has a fast rise and decay photoresponse speed at zero bias voltage, due to the self-driven photovoltaic effect which makes this heterojunction a self-powered device. This complete solution and new method of fabrication make it possible to combine different materials and flexible substrates, enhancing its potential applications in photodetectors, optoelectronic devices and sensors. [ABSTRACT FROM AUTHOR]

This paper is the first from a set of two companion papers on radio-frequency (RF) discharges. These two papers are in turn part of a larger series on the foundations of plasma and discharge physics. In this part we cover the basics of non-magnetized capacitive and inductive RF discharges, introduce the main concepts related to them and provide reference literature for further reading. In the second part we concentrate on RF discharges in the presence of external magnetic field. These types of RF discharges find a wide range of applications in various industries. Among the most prominent examples are the microelectronics industry for etching and deposition of thin films, the medical and food industry for the application of various coatings and changing the wettability of surfaces, the space industry to power ion-gridded thrusters for satellites, the fusion and elementary particle research for the production of beams of energetic ions or atoms. The paper introduces the basic concepts of RF power deposition and describes in more detail the operating conditions of the plasma reactors. The most important physical phenomena encountered in these discharges are outlined through the use of simplified models. The paper is intended as an entry point for newcomers to the field and provides ample of references (including textbooks) for further reading on the more specific and/or subtle aspects of the operation of these types of RF discharges. [ABSTRACT FROM AUTHOR]

Notwithstanding its excellent properties such as high work function and low resistance, Ru has not been widely applied in the preparation of electrodes for various electronic devices. This is because of the occurrence of severe morphological degradation in the actual devices employing Ru. Herein, we investigated Ru chemistry for electrode application and the degradation mechanism of Ru during subsequent processes such as thin film deposition or thermal annealing. We revealed that subsurface oxygen induces Ru degradation owing to the alteration of Ru chemistry by the pretreatment under various gas ambient conditions and due to the growth behavior of TiO2 deposited via atomic layer deposition (ALD). The degradation of Ru is successfully ameliorated by conducting an appropriate pretreatment prior to ALD. The TiO2 thin film deposited on the pretreated Ru electrode exhibited a rutile-phased crystal structure and smooth surface morphology, thereby resulting in excellent electrical properties. This paper presents an important development in the application of Ru as the electrode that can facilitate the development of various next-generation electronic devices. [ABSTRACT FROM AUTHOR]

The paper introduces a modified approach of time resolved in situ diagnostics of highly reactive discharges (C2H2 in our case) usually used for a deposition process of various non-conductive thin films. Reactive plasma could create an insulating film onto inserted diagnostic tools, which distorts measured data and makes their processing unreliable; a typical problem of Langmuir probe measurements. The proposed approach utilizes a so-called radiofrequency (rf) Sobolewski probe for ion flux measurement which is further modified to also obtain the electron temperature in some cases and the ion density. In this work, we introduce the procedure where measured rf probe characteristics are transformed towards I–V curves of the plasma sheath with subtracted capacitive current. This processing enables not only the monitoring of plasma sheath impedance and the ion flux towards the substrate but also allows for an estimation of other parameters as the plasma density or electron temperature, respectively. We demonstrate that the substrate used for thin film deposition can act as an active probe itself. The relevance of the proposed method was verified in pure Ar discharge where the results correspond with conventional Langmuir probe diagnostics. Furthermore, internal plasma parameters of highly reactive Ar/C2H2 plasma, formed from acetylene, were evaluated, too. [ABSTRACT FROM AUTHOR]

A knowledge-based understanding of the plasma-surface-interaction with the aim to precisely control (reactive) sputtering processes for the deposition of thin films with tailored and reproducible properties is highly desired for industrial applications. In order to understand the effect of plasma parameter variations on the film properties, a single plasma parameter needs to be varied, while all other process and plasma parameters should remain constant. In this work, we use the Electrical Asymmetry Effect in a multi-frequency capacitively coupled plasma to control the ion energy at the substrate without affecting the ion-to-growth flux ratio by adjusting the relative phase between two consecutive driving harmonics and their voltage amplitudes. Measurements of the ion energy distribution function and ion flux at the substrate by a retarding field energy analyzer combined with the determined deposition rate Rd for a reactive Ar/N2 (8:1) plasma at 0.5 Pa show a possible variation of the mean ion energy at the substrate Emig within a range of 38 and 81 eV that allows the modification of the film characteristics at the grounded electrode, when changing the relative phase shift θ between the applied voltage frequencies, while the ion-to-growth flux ratio Γig/Γgr can be kept constant. AlN thin films are deposited and exhibit an increase in compressive film stress from −5.8 to −8.4 GPa as well as an increase in elastic modulus from 175 to 224 GPa as a function of the mean ion energy. Moreover, a transition from the preferential orientation (002) at low ion energies to the (100), (101) and (110) orientations at higher ion energies is observed. In this way, the effects of the ion energy on the growing film are identified, while other process relevant parameters remain unchanged. [ABSTRACT FROM AUTHOR]

We report a type of transition metal selenide (Fe40Co40Se20) thin films supported on carbon fiber paper (CFP) (Fe40Co40Se20/CFP) and study the effects of the substrate temperature during thin film deposition on the electrocatalytic performance of the films in the oxygen evolution reaction. Fe40Co40Se20/CFP thin films were deposited by vacuum magnetron sputtering at substrate temperatures of 308, 393, and 573 K. In 1MKOH, the amorphous film deposited at 393 K exhibited better comprehensive electrocatalytic activity and stability than that of the Fe40Co40Se20/CFP thin films deposited under other conditions, achieving a low overpotential of 307 mV at a current density of 10mAcm-2 and low Tafel slope of 35mVdec-1. These results reveal that an appropriate substrate temperature during film formation improves the catalytic performance of thin film catalysts to some extent. A combination of lowcharge resistance and large electrochemically active surface area contributes to the electrocatalytic performance of the Fe40Co40Se20/CFP thin films. [ABSTRACT FROM AUTHOR]

A unified model of thin film deposition by means of sputter deposition requires a description which bridges the intrinsic time and length scales of both the solid and the gas-phase. As a proof of concept, in this work such a description is established based on machine learning techniques using artificial neural networks. Initially, sputtered particle distributions are obtained from transport of ions in matter based simulations for Ar projectiles bombarding a Ti–Al composite for a number of representative incident particle energy distribution functions. Subsequently, a multilayer perceptron network is trained and verified with this set of incident/outgoing distributions. An error analysis is carried out for the obtained training results and their quality is compared and discussed for two sets of hyperparameters. Therewith, it is demonstrated that the trained network is able to predict the sputtered particle distributions for unknown, arbitrarily shaped incident ion energy distributions. It is consequently argued that the trained network may be readily used as a machine learning based model interface, which is sufficiently accurate also in scenarios which have not been previously trained. [ABSTRACT FROM AUTHOR]

High voltage positive electrodes for lithium ion batteries have suffered from continuous oxidation of the electrolyte during cycling, which largely offsets the benefits of high energy and power densities. In this work, the electrolyte oxidation and concomitant film deposition/dissolution behaviors were investigated on Pt electrode by using linear sweep voltammetry (LSV), electrochemical quartz crystal microbalance (EQCM), and X-ray photoelectron spectroscopy (XPS). Two characteristics were identified. First, film deposition is relatively unfavorable at higher potentials (>4.7 V vs. Li/Li+) because the oxidation products are mostly gaseous or soluble species. Second, the concentration of inorganic species decreases in the surface film as the potential increases, which is likely dissolved by HF or polar species. The dominance of gaseous or soluble products and the partial dissolution of the surface film, are two characteristics which hamper passivation of the electrode surface, leading to severe electrolyte oxidation at the high potentials. [ABSTRACT FROM AUTHOR]

Effect of thin film deposition route on the morphology and performance of molybdenum oxide (MoO3) based electrochromic devices was investigated. For the deposition of thin films, a sequential deposition method, which includes ultrasonic spray pyrolysis (USP) and thermal evaporation methods was used. Films deposited solely using either USP or thermal evaporation method were used as control samples. Following deposition, MoO3 thin films were then characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy. Surface characteristics and chemical structure of the deposited thin films were found to depend extensively on the deposition route. Electrochromic performance and reversibility of the samples were evaluated using ultraviolet-visible spectrophotometer and cyclic voltammetry. Sample prepared by USP method showed low coloration efficiency (16 cm² C-1), but high stability. In contrast, sample prepared by thermal evaporation had high coloration efficiency (30 cm² C-1), but low stability. Sample prepared by sequential deposition method showed the highest coloration efficiency (33 cm² C-1) among other samples and maintained its stability with cycling. The sequential deposition route investigated in this work is highly promising and might be extended to other metal oxide systems. [ABSTRACT FROM AUTHOR]

In this article is proposed a new preparation method for composite ultra-thin films for photovoltaic application. Compounds such as Kesterites (CZTS, ternary and quaternary copper and zinc sulfides) could be used in virtue of their semiconductor behavior in conjunction with electrodeposition from aqueous media methodologies; in particular E-ALD (Electrochemical Atomic Layer Deposition) method seems a legitimate alternative to the high pressure and temperature methods used since today. We studied the feasibility of the electrodeposition process of two layers of semiconductors (CuxZnyS, with p electronic proprieties, and CdS with n electronic proprieties), one above the other, by means of E-ALD. Preliminary electrochemical studies revealed the complex nature of the composite film, impairing the anodic stripping of Cd. In order to confirm that the Cd electrodeposition is surface limited, two sets of samples were compared using different conventional and charge controlled potentiostatic electrodeposition methodologies. SEM and XPS characterization was then performed to characterize morphologically and quantitatively the samples. Consequently, the conditions for the surface limited deposition of Cd over CuxZnyS have been reckoned through the electrochemical and spectroscopical analysis. The layered (p-n) structure of the thin film has been confirmed. [ABSTRACT FROM AUTHOR]

We describe electrolyte design for bipolar electrochemical growth and patterning of a range of materials on an electrically floating substrate using the scanning bipolar cell (SBC). In the SBC, bipolar electrodeposition is driven by local potential variation generated beneath a rastering microjet anode connected to a far-field cathode. Metal reduction occurs beneath the microjet when the substrate is approached, provided the electrolyte possesses a suitable reducing agent that undergoes oxidation across the substrate far-field. We use a series of metal reduction reactions (Ni, Cu, Au, Ag) that cover a wide range of nobility, and couple them to the oxidation of ascorbic acid or ferrous ion, depending upon the metal used. The reversibility or irreversibility of the local metal reduction reaction dictates details of the required electrolyte thermodynamics. For irreversible deposits (Ni, Au), there is a wide thermodynamic operating window for the bipolar counter reaction. Reversible deposits that are easily etched (Cu, Ag) have tight thermodynamic windows; deposit stability requires the use of metastable electrolytes. We provide a simple scaling relationship that incorporates the electrolyte thermodynamics, interfacial charge transfer kinetics, and SBC operating conditions, then demonstrate its use through a 10X reduction in the spatial dimensions of local nickel reduction chemistry. [ABSTRACT FROM AUTHOR]

Manganese-doped copper interconnects are known to provide superior electromigration resistance and thus are attractive for further downscaled interconnect metallization in future high-performance microprocessors. In the present study, we report on Cu-Mn (copper-manganese) fabricated by electroless deposition. Using tartrate-complexed electrolytes, we achieved electroless plating of Cu-Mn with (4.0 ± 0.5) at.% Mn. Electrochemical studies determined the most likely oxidation state of the Mn in the deposit to be +2. This suggests incorporation of MnO or Mn(OH)2 during deposition. After heat-treatment of the Cu-Mn films, X-ray photoelectron spectroscopy indicated Mn segregation at the film surface. Moreover, transmission electron microscopy demonstrates Mn segregation at Cu-substrate interface. These observations suggest that Mn transport in electroless-deposited Cu-Mn can be exploited to engineer future interconnects with improved reliability and 'self-forming' barrier properties. Challenges to be addressed in future studies are highlighted. [ABSTRACT FROM AUTHOR]

MEMS (micro electro-mechanical systems) operated in resonance and excited piezoelectrically are nowadays used for a broad range of different application scenarios. To enhance the process stability and hence, the reproducibility of key film parameters of sputter-deposited aluminium nitride such as the film stress, the piezoelectric coefficient d _33 and low leakage current levels, a novel aluminium clamped substrate holder is reported. Compared to the standard molybdenum based solution, where the thermal contact between the wafer and substrate holder varies during deposition, as the wafer can move freely, the substrate temperature variations are substantially reduced due to clamped configuration. Independent of AlN film thickness ranging between 0.5 μ m and 2.0 μ m the scatter in piezoelectric constant d _33 and leakage current characteristics represented by the barrier height and the activation energy is reduced up to a factor of 3. These results demonstrate the importance to control carefully the temperature conditions during low-temperature AlN deposition to ensure a high reproducibility in film properties.

Electrochemical deposition and dissolution of lithium were investigated in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA-) ionic liquids containing LiTFSA through a typical inorganic lithium ion conductor, lithium phosphorus oxynitride (LiPON) thin film. In both BMPTFSA and EMITFSA containing 1 M LiTFSA, no cathodic current attributable to reductive decomposition of the ionic liquids was observed on the Ni electrode coated with the LiPON thin film. Electrochemical deposition and dissolution of Li were confirmed to occur through the LiPON thin film in both ionic liquids. Therefore, the LiPON thin film acted as an artificial solid electrolyte interphase film, in which Li ion was transported from the ionic liquids to the interface between the Ni electrode and the LiPON thin film. [ABSTRACT FROM AUTHOR]

Ag nanoparticle catalysts having a Ag@SnO2 core/shell structure were adsorbed from their colloidal solution on the smooth epoxy substrates conditioned with poly(diallyldimethylammonium chloride). The amounts and morphology of the adsorbed catalysts suggest the uniform monolayer adsorption and the formation of the agglomerated two-dimensional domains comprising several nanoparticles. Citrate acceleration of the adsorbed catalysts dissolved the SnO2 shell of the catalysts, and somewhat increased the size of the agglomerated domains and the surface roughness of the substrate with adsorbed nanoparticles. Electroless Cu deposition rate on the substrates with adsorbed catalysts went through a maximum at the initial stage, and then decreased to its constant value. Isolated Cu particles were deposited at the initial stage, and they coalesced to form the continuous films after the deposition rates reached the constant value. On the substrates without the citrate acceleration, Cu particles were deposited only at the beginning, due to the desorption of catalysts into the plating bath. The citrate acceleration prevented the desorption, and hence increased the catalyst availability. This led to the higher deposition rate and the faster morphology development at the initial stage because of the rapid and progressive deposition of Cu particles. [ABSTRACT FROM AUTHOR]

Electrodeposition of functional coatings on aluminum electrodes in aqueous solutions often is impeded by the corrosion of aluminum. In the present work it is demonstrated that electrodeposition of vanadium oxide films on nanostructured aluminum substrates can be achieved in acidic electrolytes employing a novel strategy in which a thin interspacing layer of manganese oxide is first electrodeposited on aluminum microrod substrates. Such deposited films, which were studied using SEM, XPS, XRD, and surface enhances Raman scattering as well as chronopotentiometry, are shown to comprise a mixture of vanadium oxidation states (i.e. IV and V). As this all-electrochemical approach circumvents the problems associated with aluminum corrosion, the approach provides new possibilities for the electrochemical coating of nanostructured Al substrates with functional layers of metal oxides. The latter significantly facilitates the development of new procedures for the manufacturing of three-dimensional aluminum based electrodes for lithium ion microbatteries. [ABSTRACT FROM AUTHOR]

Direct electroless deposition, i.e., without using a sacrificial anode or substrate activation, of iron-boron (FeB) films on copper substrates is reported. Electroanalytical techniques including polarization measurements of oxidation and reduction half-reactions are employed to optimize process parameters, thereby enabling direct nucleation and sustained growth of electroless FeB films on copper. Scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction are used to characterize the film morphology, the deposition rate, the deposit composition and crystallinity. Optimized electroless FeB films have a growth rate of 0.24 μm/hr, are smooth and amorphous, and exhibit acceptable corrosion resistance. [ABSTRACT FROM AUTHOR]

Since the discovery of electroless deposition within the electroplating process, the two techniques have grown as two separate, yet parallel, means of deposition. This paper demonstrates the reunification of the two processes in what is herein named hybrid electroelectroless deposition, or HEED. Specifically, the novel reunification as outlined within this study demonstrates that electroplating and electroless deposition can be achieved from a single solution wherein each process specifically targets a different metal ion within the electrolyte. The successful production of a compositionally modulated Au/Co/Au tri-layer from a single electrolyte using modulated electroless and electro-plating is described. Additionally, the practical application of producing compositionally modulated Ni-Zn-P alloy layers on AZ91D Mg alloys is demonstrated. [ABSTRACT FROM AUTHOR]

A power-modulated radio-frequency (f = 13.56 MHz) argon plasma supplied by reactive acetylene to deposit an amorphous hydrocarbon film on the electrodes is studied. The effects of gradual film deposition on electron density, electron temperature, argon metastable Arm(3P2) density, and dc-bias voltage are investigated. The time evolutions of plasma parameters during a pulsing cycle are studied as a function of the applied RF power and the thickness of the deposited film. Analytical estimations show a slower expansion of the sheath size and a slower decay of the ion flux after film deposition on the electrodes. The observed changes in the plasma parameters during the power-on and afterglow phases of the pulsed plasma can be correlated with the presence of impurities desorbed from the chamber walls in the discharge volume. [ABSTRACT FROM AUTHOR]

The effect of 2,2'-dipyridyl and 3-N.N-dimethylaminodithiocarbamoyl-1-propanesulfonic acid (DPS) during Cu electroless deposition was observed ill real time by measuring open-circuit potential and mass change of an electrode with a electrochemical quartz crystal microbalance. During Cu electroless deposition, the addition of 2,2'-dipyridyl reduced the deposition rate. DPS switched its role sensitively according to its concentration: deposition was accelerated at low concentrations and strongly suppressed at high concentrations. However, synergetic suppression effect was observed even at low DPS concentrations when 2,2'-dipyridyl was added together. In this system, the rate of suppression depended on DPS concentration: the higher DPS concentration decreased the deposition rate faster, while the minimum deposition rate was independent of the DPS concentration. Using the synergetic suppression effect, electroless Cu filling of 55-nm trenches was also successfully achieved. [ABSTRACT FROM AUTHOR]

The chalcogenide compound GaV4S8 is promising for applications as active materials in non-volatile memory applications. We report here a comprehensive study on the thin-film deposition of this compound using a stoichiometric GaV4S8 target and H2S/Ar reactive sputtering. We show that a fraction of 0.5% to 1% of H2S in the reactive plasma is sufficient to compensate the sulfur deficiency that appears in films deposited in pure Ar plasma. This reactive plasma method allows avoiding the addition of elemental sulfur during the annealing treatment required to obtain a crystallized and stoichiometric GaV4S8 layer. A simple Au/GaV4S8/Au structure presents a resistive switching behaviour well suited for non-volatile memory applications. [ABSTRACT FROM AUTHOR]

We present a lithography-free technological strategy that enables fabrication of large area substrates for surface-enhanced Raman spectroscopy (SERS) with excellent performance in the red to NIR spectral range. Our approach takes advantage of metal dewetting as a facile means to create stochastic arrays of circular patterns suitable for subsequent fabrication of plasmonic disc-on-pillar (DOP) structures using a combination of anisotropic reactive ion etching (RIE) and thin film deposition. Consistent with our previous studies of individual DOP structures, pillar height which, in turn, is defined by the RIE processing time, has a dramatic effect on the SERS performance of stochastic arrays of DOP structures. Our computational analysis of model DOP systems confirms the strong effect of the pillar height and also explains the broadband sensitivity of the implemented SERS substrates. Our Raman mapping data combined with SEM structural analysis of the substrates exposed to benzenethiol solutions indicates that clustering of shorter DOP structures and bundling of taller ones is a likely mechanism contributing to higher SERS activity. Nonetheless, bundled DOP structures appeared to be consistently less SERS-active than vertically aligned clusters of DOPs with optimized parameters. The latter are characterized by average SERS enhancement factors above 107. [ABSTRACT FROM AUTHOR]

We demonstrate an organic–inorganic-hybrid thin-film encapsulation technique for organic solar cells. The single-layer encapsulation thin film is deposited from a gas mixture of hexamethyldisiloxane and oxygen by plasma-enhanced chemical vapour deposition at room temperature. The encapsulation film contains organic and inorganic compounds: the inorganic compounds serve as the permeation barriers, and the organic compounds reduce defect propagation. An optical transmission of ⩾90% in the visible light region and a water vapour transmission rate of 3.6 × 10−6 g m−2 day are obtained for a 1.5 µm thick hybrid film. Efficiency decay is not observed in the inverted organic solar cell coated with this thin film after exposure to air for 3600 h; in contrast, the efficiency of the unencapsulated counterpart degrades rapidly and fails after exposure to air for 120 h. The obtained results show that this organic–inorganic-hybrid thin film is promising for the encapsulation of organic solar cells. [ABSTRACT FROM AUTHOR]

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation (VTE) method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition (CBD). It is found that the films deposited at a high substrate temperature (200 °C) have a preferential orientation along (002) which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV–2.56 eV. CuIn1−xGaxSe2 (CIGS) solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology. [ABSTRACT FROM AUTHOR]

Sub-15 nm-wide gratings with a high aspect ratio of up to 16:1 were fabricated using roll-to-roll nanoimprinting and plasma trimming to achieve high optical performance (up to 12 000:1 extinction ratio with an average transmittance of 82%) and low colour shift (transmittance variation less than 3%) flexible wire-grid polarizers for display applications. We applied two imprint platforms onto glass and plastic substrates to identify the optical properties and characteristics of each fabrication process. To enhance the tolerance, reproducibility, and optical performance of the process, the grating profile symmetry and varying residual layer thicknesses were precisely simulated and controlled to achieve the design targets. [ABSTRACT FROM AUTHOR]

Ru films were produced by atomic layer deposition (ALD) with an alternating supply of bis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)2) and ozone at deposition temperatures of 225-275°C. Ozone acted as an effective reactant for Ru(EtCp)2. The Ru film thicknesses formed during one cycle were saturated at relatively high values of 0.09-0.12 nm/cycle depending on the deposition temperatures, and their resistivities were about 16 µ Ω cm. Moreover, a reduced nucleation delay was found for Ru ALD using ozone when compared to Ru ALD using oxygen gas. The amount of oxygen impurity incorporated into the Ru films was less than 1 at%, as determined by Auger electron spectroscopy. The interfacial adhesion property between Ru films prepared via ALD using ozone (ozone-Ru) and ZrO2 was good and 80% step coverage was achieved on a 3-D structure with a very high aspect ratio of 16:1, making them suitable for use as a top electrode material. [ABSTRACT FROM AUTHOR]

Aluminum-doped ZnO (AZO) thin films with thin film metallic glass of Zr50Cu50 as buffer are prepared on glass substrates by the pulsed laser deposition. The influence of buffer thickness and substrate temperature on structural, optical, and electrical properties of AZO thin film are investigated. Increasing the thickness of buffer layer and substrate temperature can both promote the transformation of AZO from amorphous to crystalline structure, while they show (100) and (002) unique preferential orientations, respectively. After inserting Zr50Cu50 layer between the glass substrate and AZO film, the sheet resistance and visible transmittance decrease, but the infrared transmittance increases. With substrate temperature increasing from 25 °C to 520 °C, the sheet resistance of AZO(100 nm)/Zr50Cu50(4 nm) film first increases and then decreases, and the infrared transmittance is improved. The AZO(100 nm)/Zr50Cu50(4 nm) film deposited at a substrate temperature of 360 °C exhibits a low sheet resistance of 26.7 Ω/□, high transmittance of 82.1% in the visible light region, 81.6% in near-infrared region, and low surface roughness of 0.85 nm, which are useful properties for their potential applications in tandem solar cell and infrared technology. [ABSTRACT FROM AUTHOR]