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[Display omitted] • Wet etching of (0 0 1) plane β -phase Ga 2 O 3 (β -Ga 2 O 3) under UV illumination was investigated. • The etching behavior of the (0 0 1) plane β -Ga 2 O 3 was compared with those of (2 ¯ 01) and (0 1 0) plane. • The oval line-shaped etch pit along [0 1 0] direction was observed on the etched (0 0 1) plane β -Ga 2 O 3. The photochemical (PC) wet etching behavior of (0 0 1) plane β -phase Ga 2 O 3 (β -Ga 2 O 3) single crystal was investigated using potassium hydroxide etchant solution under ultraviolet illumination in the temperature range of 80–95 °C. The etch rate was 1.65 nm/min at 80 °C, and increased up to 4.88 nm/min at 95 °C. The etch rate of the (0 0 1) plane β -Ga 2 O 3 shows strong temperature dependence with the activation energy of 0.798 eV. The PC wet etching characteristics of the (0 0 1) plane β -Ga 2 O 3 was compared with those of (2 ¯ 01) and (0 1 0) plane β -Ga 2 O 3. The etch rates increased in order of the (0 1 0), (2 ¯ 01) , and (0 0 1) plane, which is accordance with the increasing surface energy trend. The oval line-shaped grooves aligned along [0 1 0] direction were observed on the etched (0 0 1) plane β -Ga 2 O 3 crystal surface after 30 min. PC wet etching at 80 °C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combination of picosecond laser direct writing and characterization to study the properties of picosecond laser-modified SiC surface layers. • The evolution of the energy density in relation to the modified layer structure is revealed. • The reason for the sub-surface damage mechanism of picosecond laser modification is illustrated. • Laser modification can effectively reduce the hardness of silicon carbide and improve its machinability. The stable structure, high hardness, and brittleness of single-crystal 4H-SiC present challenges in achieving efficient and damage-free polishing processing. Ultra-short pulsed laser-induced surface modification provides a new solution to enhance the manufacturability of 4H-SiC. This paper aims to investigate the underlying mechanism of the picosecond laser-induced surface structural changes in 4H-SiC and the process of material removal from solid to vapour, elucidating the interaction mechanism between picosecond laser and 4H-SiC. A temperature gradient distribution model for picosecond laser irradiation on 4H-SiC was built to reveal the formation mechanism of subsurface crack damage. The results show that a combination of phase explosion and thermal effects controlled picosecond laser-modified 4H-SiC surfaces deposited spherical SiO 2 particles and the process. The study demonstrates that the cracking behaviour in the subsurface of picosecond laser-modified SiC predominantly occurs in the recast region. The fundamental cause of cracking is attributed to the tensile stresses generated by thermal effects and the volumetric changes in the molten material resulting from the overlapping of neighbouring spots in alternating hot–cold cycles. The nanoindentation demonstrated that laser modification can effectively enhance the machinability of SiC. The findings of this study can provide a theoretical basis for efficient non-destructive machining of hard and brittle materials. [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] • Single-crystal Cu(1 1 1) is prepared on the basis of direct bonding copper method. • Specific crystal orientation relationship exists between Cu(1 1 1) and sapphire. • Cu(1 1 1) by direct bonding copper benefits the growth of single-crystal graphene. Considering the significant advantages of single-crystal Cu(1 1 1) in the synthesis of 2D materials and many other fields, its controllable preparation has attracted widespread attention. However, the formation of a single-crystal Cu foil has always been hindered by competition among grains with different orientations. Herein, single-crystal Cu(1 1 1) was prepared on the basis of the traditional direct bonding copper method. Cu foil and c-plane sapphire substrate were bonded through Cu 2 O at high temperature. After the reduction of Cu 2 O by H 2 , the surface crystal structure of sapphire will guide Cu to form single-crystal Cu(1 1 1). The single-crystallinity of Cu(1 1 1) and the specific orientation relationship between Cu(1 1 1) and sapphire were confirmed by LEED and XRD. Furthermore, the growth of high-quality single-crystal graphene was performed on single-crystal Cu(1 1 1). This work not only facilitates the mass production of 2D materials such as single-crystal graphene, but also provides greater application potential to the direct bonding copper technology and single-crystal Cu. [ABSTRACT FROM AUTHOR]

Possible mechanism diagram of the roles of oxygen vacancies in LaFeO 3 photocathodes in photoelectrochemical water splitting. [Display omitted] • A molten salt method for preparing Vo modified LaFeO 3 was demonstrated. • Proper amount of Vo can enhance bulk conductivity and light utilization of LaFeO 3. • The charge carrier density of LaFeO 3 in PEC reaction is not in line with the amount of Vo. • The optimal Vo loaded LaFeO 3 exhibits 3.27 times IPCE higher than that of the pristine LaFeO 3. In this study, we prepared oxygen vacancies (V O) modified LaFeO 3 particles using a simple molten salt method by tuning the cation (La3+) deficiency. The existence of V O was confirmed by studying its crystal structure and surface chemical state. By testing the photoelectrochemical (PEC) activity of the Vo modified La 1-x FeO 3-σ photocathodes in a 0.1 M NaOH electrolyte under visible light, the results demonstrate that the as-prepared La 0.9 FeO 3-σ shows good stability and superior IPCE, which is 3.27 times that of the pristine LaFeO 3. Even through V O modification is an effective strategy for regulating the PEC performance of a semiconductor, the charge carrier density in semiconductor is not directly proportional to the amount of V O , as excessive V O may lead to deterioration of the electrochemical reaction due to interfacial charge recombination. Introducing suitable amount of V O into LaFeO 3 can improve the light absorption, boost charge carrier transfer and separation efficiency, narrow the bandgap, and enhance the electrocatalytic reaction dynamics at the semiconductor surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dissociation of 0.7–1.9 eV supersonic CH3Cl molecules on Cu(1 1 1) • Cl as the dominant adsorbed species coming from the dissociative scattering of CH3Cl. • Identification of the adsorbed species using SR-XPS. • The threshold kinetic energy of the dissociative reaction depending on the crystal. • surface orientation. To study the elementary steps in the Rochow-Müller process, we bombarded Cu(1 1 1) and Cu(4 1 0) with 0.7–1.9 eV supersonic molecular beams (SSMB) of CH 3 Cl. We then identified the corresponding adsorbed species using X-ray photoemission spectroscopy (XPS) in conjunction with synchrotron radiation (SR). We found Cl as the dominant adsorbed species (much higher than that of adsorbed carbonaceous species) coming from the dissociative scattering of CH 3 Cl. We also found that the threshold kinetic energy of the reaction depends on the crystal surface orientation. [ABSTRACT FROM AUTHOR]

The behavior of polar metal organic molecules, chloroaluminum phthalocyanine (ClAlPc), upon ultraviolet (UV) irradiation was investigated to evaluate the stability of the adsorption process on the Ag(111) thin film and bulk crystal. Photoelectron spectroscopy (PES) was mainly employed to measure the molecular energy states (MES) and vacuum level (VL) shift for 1-ML ClAlPc in the Cl-down configuration. A consistent trend was observed showing that ClAlPc in the Cl-down configuration is energetically more stable on the Ag thin-film surface than on the corresponding surface of the Ag bulk crystal. The intermediate adsorption state in tilted configuration during the irradiation impinging is identified by large positive VL shifts and broad spectra line shapes to infer a flipping mechanism from Cl-down to Cl-up configuration. Strain on the Ag thin films from the underlying lattice-mismatched Ge(111) substrate is considered to cause enlarged hollow sites on the Ag(111) thin-films, that anchor the Cl-down configuration more tightly on the thin-film surfaces, as confirmed by density functional theory (DFT) calculations. • Using irradiation effects to study the adsorption stability of polar-organic molecule on metal surfaces. • The adsorption configurations of ClAlPc, Cl-up, Cl-down and tilted, are well characterized by the photoemission spectra. • The more anchoring stability of Cl-down ClAlPc on thin Ag films than on the bulk Ag(111) crystal surface is discovered. • Strain on Ag thin films is considered to cause the Cl-down configuration more stable, as confirmed by DFT calculation. [ABSTRACT FROM AUTHOR]

Thanks to a dedicated modelling of intensities, the depth sensitivity of X-ray photoemission is used to probe the segregation profile of aluminium at the (110), (100) and (111) low index surfaces of the body-centred Fe 0.85 Al 0.15 random alloy. Sputtered surface composition is close to the nominal bulk one, thus excluding preferential sputtering. Surface enrichment in aluminium upon annealing starts at around 700 K before reaching a stationary state above 1000 K. The average surface composition is close to Fe 0.5 Al 0.5 , corresponding to the B 2 CsCl structure of the phase diagram. The impacted depth, that is in the range of 2.5–3.5 nm, is quite significant. Although not evidenced previously in surface science conditions at FeAl single crystal surfaces, it is qualitatively in agreement with the segregation at grain boundaries and shear planes of Al-alloyed steels. This segregation tendency is rationalized through ab initio calculations. Unlabelled Image • Severe aluminium segregation above 700 K at the surfaces of bcc Fe 0.85 Al 0.15 • Photoemission determination of the concentration profile in a random alloy • Nanometer deep impacted layer with a Fe 0.5 Al 0.5 composition • Ab initio modelling of segregation trends [ABSTRACT FROM AUTHOR]

The determination on work function of NdB 6 (1 0 0) crystal surface by both theory and experiment. [Display omitted] • The band structures of NdB 6 (1 0 0), (1 1 0), (1 1 1), (2 1 0) crystal surface are studied. • A high-quality NdB 6 single crystal is prepared by the optical floating zone method. • The Φ of the NdB 6 (1 0 0) crystal surface has been determine to be around 2.80 eV. • The PWFD on the NdB 6 (1 0 0) crystal surface suggests its good emission uniformity. In this paper, the work function Φ of the NdB 6 (1 0 0) crystal surface have been determined by both theory and experiment. By the first-principles calculation, the Φ of NdB 6 (1 0 0), (1 1 0), (1 1 1) and (2 1 0) crystal surfaces obey the relation of Φ (1 0 0) < Φ (2 1 0) < Φ (1 1 0) < Φ (1 1 1) , and the theoretical value of Φ for (1 0 0) crystal surface is calculated to be 2.791 eV. The UPS measurement and the experiments of thermionic emission have been performed on the high-quality [1 0 0] NdB 6 single crystal, which is prepared by the method of two optical floating zone melting passes. The Φ of the NdB 6 (1 0 0) crystal surface has been calculated to be 2.806 eV by the UPS measurement, while the average Φ eff of the NdB 6 (1 0 0) crystal surface is calculated to be 2.813 ± 0.109 eV. The good agreement between theoretical and experimental results indicates that the Φ of the NdB 6 (1 0 0) crystal surface can be determined to be around 2.80 eV. Furthermore, the narrow Φ distribution range and the low FWHM extracted from the Miram curves and PWFD plots suggest the good emission uniformity of the NdB 6 (1 0 0) crystal surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • For the first time, a facile surface treatment with polyethyleneimine can control the chemical interaction with tellurium atoms, which resulted in controlled crystal orientation and surface coverage. • Nanocrystalline tellurium based thin film transistor, which was led by facile surface treatment, has mobility of 21.1 cm2/Vs and I on /I off ratio of 104 with low standard deviation. • CMOS circuits made with nc -Te and a -IGZO provide a practical approach to producing high-performance and large-area on-chip device applications. Although facile fabrication of high-performance thin-film transistor (TFT)-based complementary metal oxide–semiconductor (CMOS) circuits over a large area has generated significant interest, the lack of reliable and uniform p -type TFTs is hindering it. In this study, we prepared high-performance CMOS circuits using room temperature deposited nanocrystalline tellurium (nc -Te) and sputtered amorphous-indium gallium zinc oxide (a -IGZO) TFTs. The facile polyethyleneimine (PEI) surface treatment enabled Te atom anchoring and crystal orientation control along with continuous surface coverage, resulting in a high-performance TFT with an average mobility of 21.1 cm2V−1s−1 and an I on /I off ratio of 104. By introducing monolithic integration of nc -Te and a -IGZO TFTs, various CMOS circuits including inverter, NAND, and NOR circuits were fabricated and operated quite logically. Moreover, seven-stage ring oscillators comprising 14 cross-wired TFTs validated the cascading of multiple stages and device uniformity of the complementary system, achieving an oscillation frequency up to 392.16 kHz at V DD of 20 V. nc -Te on a PEI-treated surface offers a general route to producing high-performance and stable p -type semiconductors while ensuring compatibility with standard CMOS processing and large-scale on-chip device applications. [ABSTRACT FROM AUTHOR]

By using solution plasma modification, oxygen vacancies were added to the surface of 001-faceted TiO 2 , and terminal hydroxyl groups were added to the surface of 101-faceted TiO 2 , to improve their photoreduction and photooxidation abilities, respectively. [Display omitted] • Plasma-induced active species display a facet-dependent impact on TiO 2. • The plasma introduces oxygen vacancies to T001 to improve photoreduction activity. • The plasma introduces hydroxyl groups to T101 to improve photo-oxidation ability. • Plasma offers an approach to tailor the surface of photocatalysts for versatile applications. In this paper, we construct differently exposed crystal surface structures by a novel water-plasma surface modification method to enhance specific photocatalytic reactions. Water plasma treatment of 001-faceted TiO 2 (T001) results in 2-fold and 12-fold increased photoactivity for hydrogen evolution and nitrogen fixation but significantly deteriorates its oxidation capability for photodegrading bisphenol A (BPA) contaminants. In contrast, treating 101-faceted TiO 2 (T101) under the same conditions accelerates the photodegradation of pollutants while weakening the photoreduction activity. Advanced characterizations reveal that water plasma treatment generates oxygen vacancy defects in T001, which can act as electron traps for improving the photoreduction capability. Differently, the surface hydroxyl groups on T101 caused by plasma discharging facilitate the generation of hydroxyl radicals, thus increasing its oxidation capability for contaminant degradation. This study not only sheds light on the relationship between the structure and activity of TiO 2 photocatalysts, but also presents a simple method for modifying the surface active sites through water plasma treatment. [ABSTRACT FROM AUTHOR]

Recently, demands for magneto-optical (MO) materials with high laser-induced damage thresholds (LIDT) increased rapidly with the continuous development of high power lasers. In order to study the effect of substrate defects on LIDT of (BiTm) 3 (GaFe) 5 O 12 films, in this study, (BiTm) 3 (GaFe) 5 O 12 films without gadolinium gallium garnet (GGG) substrates and (BiTm) 3 (GaFe) 5 O 12 /GGG films were prepared by liquid-phase epitaxial (LPE) and mechanical lapping and polishing method. The optical and magneto-optical properties, crystal structure, LIDT and laser-induced damage morphologies of the prepared films were investigated. Experimental results pointed out that epitaxial (BiTm) 3 (GaFe) 5 O 12 films have very high crystal and surface quality. A discontinuous defective layer with thickness of about 0–500 nm is located between GGG substrates and epitaxial films. Laser-induced damage tests and damage morphologies demonstrate that the discontinuous defective layers have an important effect on LIDT of epitaxial films, and LIDT of epitaxy films can be significantly improved by removing GGG substrates and discontinuous defective layers. • Discontinuous defective layers have an important effect on epitaxial film's LIDT. • Removing GGG substrates and discontinuous defective layers can significantly improve epitaxial film's LIDT. • The method proposed creates conditions for the wider application of epitaxial films in high power lasers. [ABSTRACT FROM AUTHOR]

The stability of the Nitrogen-polar (000-1) surface of single-crystal bulk GaN substrates is studied for layers grown by plasma-assisted molecular beam epitaxy (PAMBE) in Nitrogen-rich conditions at 730 °C. It is shown that smooth GaN layers with parallel atomic steps are obtained for substrates when the surface crystal miscut angle is larger than 2o, revealing a highly stable epitaxial growth regime on single crystals. A step meandering pattern is observed on layers grown on lower miscut angle substrates. The meandering periodicity is found to have an inverse dependence on growth rate and miscut angle. This is opposite to what is observed for epitaxy on the Ga-polar surface. Combining analytic modeling and kinetic Monte Carlo simulations, it is shown that the existence of an Ehrlich-Schwoebel Barrier (ESB) in the PAMBE growth of GaN in nitrogen-rich conditions on (000-1) GaN reproduces the experimentally observed periodicity of step meandering. Assuming that ESB height depends on interactions between diffusing adatoms, all experimental phenomena are reproduced. • Nitrogen-rich growth of high quality GaN layers in plasma-assisted MBE • High miscut angle bulk N-polar GaN substrates used to obtain atomically smooth layers • Meandering steps with periodicity increasing with increasing inter step distance • kMC simulations reproduce experimental results assuming Ehrlich-Schwoebel barrier dependent on the adatom concentration [ABSTRACT FROM AUTHOR]

Abstract Chitosan modified cuprous oxide (Cu 2 O-CTS) were prepared via facile chemical reduction method. The morphology and structure of Cu 2 O-CTS nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The catalytic ability of Cu 2 O-CTS, both in photocatalysis and electrocatalysis, was carried out on p-nitrophenol reduction. In comparison with the pristine Cu 2 O, Cu 2 O-CTS exhibits improved photocatalytic abilities with the reduction rate increased by 1.7 times. The catalytic capacity increases along with the increased proportion of CTS in Cu 2 O-CTS nanoparticles. Cu 2 O-CTS modified electrodes shows enhanced electrocatalytic capacities as well, with more positive reduction peak potential and higher peak current. Based on the experimental results, a catalytic mechanism for p-NP reduction over Cu2O-CTS catalysts is proposed. The improvement might come from the reduced band gap energy after the chitosan modification, thus Cu 2 O-CTS nanoparticles have higher catalytic activity. On the other hand, the more beneficial (111) crystal surface involves in the improvement as well, which endows Cu 2 O-CTS stronger activity and interaction with p-nitrophenol. Highlights • Chitosan modified cuprous oxide (Cu 2 O-CTS) were successfully prepared. • Cu 2 O-CTS showed improved photocatalytic/electrocatalytic abilities on p-NP reduction. • Improvement related to the reduced band gap energy and the more (111) crystal surface. [ABSTRACT FROM AUTHOR]

Abstract One-dimensional antiferromagnetic atomic chains have potential applications in information storage and spintronics devices. NiO chains have been assembled on the Ni(110) single crystal surface, and the antiferromagnetic spin order has been determined by the first-principles calculations. Scanning tunneling microscope simulation clearly distinguishes two types of Ni with opposite spin-orientations. Therefore, the information carried by such system is possible to be read out. Furthermore, we have introduced the CO molecules, which zipper the neighboring NiO chains and greatly enhance the inter-chain spin coupling. The incorporation of CO has been verified by the low energy electron diffraction and the infrared spectroscopy. Graphical abstract Unlabelled Image Highlights • We reported the assembly of NiO atomic chains on the Ni(110) substrate. • The AFM states is readable in terms of the distinguishable charge density. • NiO chains possess the magnetic bistability feature due to the AFM spin ordering. • CO molecule is able to enhance the inter-chain exchange interaction. [ABSTRACT FROM AUTHOR]

Abstract Here we demonstrate the adsorption behaviors of typical deposition-targeted metallic (Ag, Cu or Ni) ions on thiol-end surfaces during electroless deposition using for fabricating flexible electronics. Specific thiol-containing silane molecules were assembled onto the corona activated liquid crystal polymer surfaces and then metallic ions were adsorbed onto the modified surfaces. By using X-ray photoelectron spectroscopy, scanning electron microscope and atomic force microscope, the assembly processes, inter-reaction mechanism of these ions with thiol-end groups, and adsorption behaviors have been investigated in details. Thickness of the molecule layer was estimated as some nanometers. Besides, zeta-potential and wettability were used to characterize the surfaces and verify the adsorption behaviors. Overall, this work provides a helpful contribution for understanding circuits' deposition processes and fabricating flexible patterns for electronic devices. Graphical abstract Unlabelled Image Highlights • Specific thiol-containing silane was assembled onto the corona activated LCP surface. • Typical deposition-targeted metallic ions were adsorbed onto the modified surfaces. • Thickness of molecule layer was estimated as some nanometers. • The adsorption behavior and inter-reaction mechanism have been studied in details. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we studied the femtosecond laser induced periodic surface structures (fs-LIPSS) formation on LiNbO 3 :Fe crystal with the assistance of elevated temperature. Uniform deep-subwavelength fs-LIPSS with the period of 190 ± 10 nm was successfully fabricated on crystal surface as the sample temperature was at 1000 °C. And the measurement of Transmission Electron Microscopy showed that fs-laser treated samples remained crystalline. We believed that thermal excitation plays a critical role in the formation of fs-LIPSS. The initial carrier density of LiNbO 3 :Fe are effectively increased during this process, and high concentration surface carriers are effectively excited by femtosecond laser irradiation, which make great contribution to formation of fs-LIPSS. Moreover, we also found that the doped Fe2+ ions are conducive to the fs-LIPSS formation. The iron doped LiNbO 3 crystal with uniform surface structure has great application prospects in related fields, such as on-chip photonic-integrated platforms, nanophotonics, and nanostructures for micro-fluidics. Highlights • Uniform deep-subwavelength fs-LIPSS were fabricated on LiNbO 3 :Fe surface at 1000 °C. • Thermal excitation plays a critical role in the formation of fs-LIPSS. • Compared with pure LiNbO 3 , the doped Fe2+ ions contribute to the fs-LIPSS formation. • Transmission Electron Microscopy show fs-LIPSS is recrystallized as original structural phase. • This method can apply for other dielectric materials to fabricate micro-/nano-device. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ce 2 (SO 4) 3 was designed to chemical looping partial oxidation of methane. • Appropriate E vac plays a critical role in adsorption and dehydrogenation process. • O v facilitates the adsorption and dehydrogenation process. • Increasing the O v concentration does not continue to reduce the energy barrier. • Compared to other surfaces, (0 0 1) surface has a better reaction performance. We present a first principles study using periodic density functional theory on the reaction between Ce 2 (SO 4) 3 oxygen carrier and CH 4 during chemical looping partial oxidation. The (0 0 1) surface has an appropriate bond strength and oxygen vacancy (O v) formation energy (E vac). Further analysis shows that CH 4 has a weak adsorption performance on (0 0 1) surface, while CH x (x = 0–3) radicals have a strong electron density overlap. The lattice oxygen atoms tend to leave the crystal surface during adsorption process, which is conducive to the syngas formation. Compared with (1 0 2) surface, (0 0 1) surface has a lower dehydrogenation and syngas formation energy barrier. CH 3 → CH 2 + H serves as the rate-determining step on (1 0 2) surface, while on (0 0 1) surface is CH 2 → CH + H (TS3). O v effects are emphasized through the comparison of (1 0 2), (0 0 1) and O v (0 0 1) surface. The corresponding energetic results show that the O v facilitates the adsorption and dehydrogenation process. But when the O v concentration is larger than 1.96%, increasing the O v concentration does not continue to reduce the energy barrier of TS3. In summary, (0 0 1) surface has a better reaction performance, and O v play a critical role in both adsorption and dehydrogenation process. [ABSTRACT FROM AUTHOR]

This paper proposed a novel spatial frequency analysis method for the investigation of potassium dihydrogen phosphate (KDP) crystal surface based on an improved bidimensional empirical mode decomposition (BEMD) method. Aiming to eliminate end effects of the BEMD method and improve the intrinsic mode functions (IMFs) for the efficient identification of texture features, a denoising process was embedded in the sifting iteration of BEMD method. With removing redundant information in decomposed sub-components of KDP crystal surface, middle spatial frequencies of the cutting and feeding processes were identified. Comparative study with the power spectral density method, two-dimensional wavelet transform (2D-WT), as well as the traditional BEMD method, demonstrated that the method developed in this paper can efficiently extract texture features and reveal gradient development of KDP crystal surface. Furthermore, the proposed method was a self-adaptive data driven technique without prior knowledge, which overcame shortcomings of the 2D-WT model such as the parameters selection. Additionally, the proposed method was a promising tool for the application of online monitoring and optimal control of precision machining process. [ABSTRACT FROM AUTHOR]

The growth of hexagonal crystals of the 4H-SiC and 6H-SiC polytypes occurs in the 〈0001〉 direction. The exposed crystal surface is composed of terraces of the {0001} oriented crystal planes separated by atomic steps of half-unit-cell or single-unit-cell height. We present results of density functional theory (DFT) study of the atomic structure and morphology of the atomic steps formed in the [ 10 1 ¯ 0 ] and [ 11 2 ¯ 0 ] directions on the Si-terminated 4H-SiC{0001} and the C-terminated 4H-SiC { 000 1 ¯ } surfaces. On the latter surface atomic and electronic structure is modified only in the nearest neighbourhood of the step whereas the structure of the terrace is almost unchanged compared to that of the smooth stoichiometric surface. In contrast, on the Si terminated surface for both types of the applied model steps and on the widest terraces considered a substantial surface buckling is observed in the regions between steps. We calculated ledge energy and found that [ 11 2 ¯ 0 ] step with C atom on the edge at Si-terminated surface is the most favourable energetically of all examined cases. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three typical pyrite crystal surfaces of {1 0 0}, {1 1 1},{2 1 0} have been investigated. • The overall oxidation rate follows the order of {2 1 0} > {1 1 1} > {1 0 0}. • H 2 O has the greatest affinity for the {2 1 0} surface but does not dissociate. • O 2 adsorb and dissociate on pyrite surfaces in the order of {1 1 1} > {2 1 0} > {1 0 0}. • Slower oxidation rates are observed on individual pyrite surfaces than with pyrite powders. The oxidation of pyrite has attracted significant attention due to its predominant contribution to the serious environmental issue of acid mine drainage (AMD). However, relatively few studies have been conducted investigating the oxidation characteristics of individual pyrite crystal faces. The oxidation rates, under acidic, neutral and alkaline conditions, of three typical pyrite surfaces have been examined with their contrasting behaviors explored in terms of surface structure. Electrochemical and surface analytical measurements were conducted across the pH range 1 to 11, showing surface formation of Fe(OH) 3 , S0 and SO 4 2−. Tafel plots, electrochemical impedance spectroscopy and surface analyses demonstrate that the oxidation rate follows the order of {2 1 0} > {1 1 1} > {1 0 0}. This rate trend is directly related to the breakage of bonds on surface formation with formation of the {2 1 0} surfaces requiring the greatest bond breakage; hence this surface is the most unstable, and the {1 0 0} surface owns the least bond breakage and the greatest stability. The oxidation rate of all pyrite surfaces under strongly acidic conditions (pH = 1) is greater than for strongly alkaline conditions (pH = 11), with the slowest rates being observed under neutral condition, since S0, iron oxyhydroxide (Fe-OOH) and Fe(OH) 3 formed under neutral or alkaline conditions cover the pyrite surface, thus inhibiting further oxidation. However, a more aggressive oxidant of hydroxo–Fe(III) complex is present under alkaline conditions, resulting in greater oxidation rate compared to that under neutral conditions that determined by the oxidation of Fe2+ by O 2. DFT calculations suggest that H 2 O has the greatest affinity for the {2 1 0} surface as compared to the {1 0 0} and {1 1 1} surfaces but does not dissociate. However, after the dissociative adsorption of O 2 , H 2 O can dissociate on all the pyrite surfaces, enhancing further oxidation. Under acidic conditions this process is likely to be rate determining. Under alkaline and neutral conditions the oxidation process is dependent on the transfer of hydroxyls to the surface S group and surface cycling of Fe(II) − Fe(III). [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple hydrothermal method facilitates one-step synthesis of high-performance amorphous ZnO/crystalline Sn 3 O 4. • The sequential-crystallization-based adsorption inducted design promotes the interfacial coupling of amorphous ZnO and Sn 3 O 4. • The hierarchical pore structure of heterojunction increases the oxygen vacancy concentration and provides more transport channels. • Removal efficiency of 0.2 g/L Cr(VI) in 100 min was as high as 59 %. This paper is devoted to the construction of amorphous/crystalline heterojunction by a simple one-step hydrothermal method to realize the effective photocatalytic reduction of high concentration chromium. Taking amorphous ZnO/crystalline Sn 3 O 4 (Z/S) as an example, the precursor of Sn(II) preferentially formed crystalline Sn 3 O 4 based on the difference of complex constant (1010.8 vs 104.4). The precursor of Zn(II) is then hydrolyzed and bonded to the surface of Sn 3 O 4 by sn-O-Zn. The capping effect produced by citric acid selective adsorption on crystal surface significantly improves the proportion and stability of amorphous ZnO (aZnO). Interestingly, the introduction of aZnO transformed the surface structure of the Sn 3 O 4 from micropore to hierarchical pore structure, which accelerated the adsorption of pollutants. The typical catalytic and characterization result illustrated that rich interfacial chemical bonds, abundant of oxygen vacancies and high interfacial potential energy difference collectively expedite the photoreduction of Cr(VI) on Z/S heterojunction. Up to 95.6 % (60 min for 0.1 g/L) and 59.1 % (100 min for 0.2 g/L) removal efficiency, importantly, proved that sequential-crystallization-based adsorption inducted design has advantages in the simple construction of high-quality amorphous heterostructures. [ABSTRACT FROM AUTHOR]

Snapshots of evolution of deuterium bubbles below the (1 1 1) surface of tungsten, exposed to the flux of 6. 24×1028 m−2s−1 and 80 eV deuterium atoms at 300 K. The red spheres represent the tungsten atoms and the blue spheres represent the deuterium atoms. The black dashed lines represent the original boundary of the tungsten atoms. [Display omitted] • D bubble evolution process is divided into three stages: formation, growth, and burst and it are significantly influenced by temperature, flux, and energy, which is revealed by molecular dynamics methods. • The evolution of deuterium bubbles under various crystal surfaces reveals that it was found to be more difficult under a surface with a higher crystal face density. • By calculating the internal pressure, volume, and molecular ratio (D in D 2)/D of deuterium bubbles, the mechanism of deuterium atoms forming molecules and then forming deuterium bubbles is proposed. Using molecular dynamics simulations, the Tersoff-potential was used to investigate the evolution of deuterium (D) bubbles in tungsten (W). This work documents the entire evolution process of D bubbles: formation, growth and burst. The effects of flux, temperature and incident energy of D on the evolution and position of D bubbles were discussed. Temperature and flux together affect the time required for D bubble formation, and energy has a significant effect on depth. At 300 K, single-crystal tungsten surfaces (0 0 1), (1 1 0), (1 1 1), and (1 1 2) were bombarded by D atoms with 80 eV energy and 6.24 × 1028 m−2s−1 flux. Although all D bubbles go through three stages, the pressure, volume, and the ratio of (D in D 2)/D inside bubbles can tell the difference between the four surfaces. Under the same simulation conditions, the evolution of D bubbles under a surface with a higher crystal face density was found to be harder. [ABSTRACT FROM AUTHOR]

The inorganic anions can change the crystal phase of ZnIn 2 S 4 , and accompany the exposure of different crystal planes under the same pH condition. With zinc chloride and indium nitrate as metal precursors, the hydrothermal reaction was carried out at pH=1.0 to inhibit the production of In(OH) 3. The results show that the cubic ZnIn 2 S 4 can be transformed into hexagonal phase under the action of Cl− and SO 4 2−, and the (1 0 2) and (0 0 6) crystal surfaces are exposed, respectively. with the assistance of NO 3 −, the crystal phase of ZnIn 2 S 4 does not change, but the (3 1 1) crystal face of cubic phase is exposed. [Display omitted] • The type of inorganic anions influenced the crystal phase of ZnIn 2 S 4. • Cubic and hexagonal phases can interconvert. • (1 0 2) and (3 1 1) are the active planes of hexagonal and cubic phase. • ZIS-ZnCl 2 -pH H2SO4 with (1 0 2) plane has excellent photocatalytic performance. • The degradation mechanism of HTC by ZIS-ZnCl 2 -pH H2SO4 was proposed. A series of polymorphous ZnIn 2 S 4 was successfully synthesized by changing the type of metal precursor and inorganic acid that adjust the pH value of hydrothermal reaction system to 1.0, and the mutual conversion between cubic and hexagonal phase had been triumphantly implemented under controllable conditions. Among them, the addition of acid mainly inhibits the production of In(OH) 3 , and the inorganic anions affect the crystal structure of the material under the same pH value, including crystal phase and crystal plane, which could be attributed to the electronegativity and polarity between inorganic anions (Cl− > NO 3 − > SO 4 2−). ZIS-ZnCl 2 -pH H2SO4 had better photocatalytic performance and stability, the apparent quantum yield reached 18.45%, which the removal rate of tetracycline hydrochloride (HTC) and Cr(VI) reached 95.18% and 99.85% in 120 min, respectively. The relationship between the structure and properties of ZIS-ZnCl 2 -pH H2SO4 proved that SO 4 2− can make cubic transform hexagonal phase, and promote the (1 0 2) crystal plane of hexagonal phase preferentially grow and expose more active sites, thus improving the photocatalytic activity. This work provides an effective method to construct different crystal structure of ZnIn 2 S 4 with highly exposed active crystal phase. [ABSTRACT FROM AUTHOR]

Fig. 1 photocatalytic charge transfer and reaction mechanism of 500Ca-BiOBr. [Display omitted] • BiOBr nanosheets responding to visible light were prepared at room temperature and pressure. • CaCO 3 as a structure-directing agent changes the main exposed crystal plane of BiOBr from the (1 0 2) facet to the (1 1 0) facet. • CaCO 3 increased the specific surface area of BiOBr nanosheets. The modulation of crystal surface is one of the important means of photocatalyst modification. BiOBr photocatalyst with exposed (1 1 0) facets was synthesized at room temperature and pressure using CaCO 3 as a directing agent in this experiment. The addition of CaCO 3 not only promoted the exposed facets of BiOBr from (1 0 2) to (1 1 0), but also improved its ability of photocatalytic degradation of pollutants, meanwhile, changed the specific surface area of BiOBr, provided more active sites, and enhanced the adsorption capacity of BiOBr. At the same time, the effects of different alkaline earth metals on the performance of BiOBr photocatalytic materials were compared, it was determined that the degradation rate of RhB of BiOBr photocatalyst reached 97% within 60 min when adding 500 wt% CaCO 3 , and the main active group in the degradation experiment was h+. In conclusion, BiOBr with different main exposed facets was prepared in this paper, and a new idea was provided for alkaline earth metals in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

A new class of molecular modifiers, i.e. natural polyphenols, inspired from Chinese tea has been discovered for CaOx crystallization inhibition. These polyphenol modifiers display a unique dual action of growth promoter and inhibitor dependent upon their concentrations. The unexpected, remarkable growth promotion reaches a new record up to 75%, leading to the formation of macroscopic crystal whiskers by change in growth mode from spiral-mediated to generation of 2D islands and layer spreading mechanism and concurrent growth of step bunches (not seen commonly). [Display omitted] • Calcium oxalate crystal whiskers were induced by natural polyphenols on COM (0 1 0) surfaces. • Step growth mode was changed from spiral dislocation to 2D layer growth. • Adsorbed polyphenols on surface inhibited step advancement and induced the formation of step bunches. • The governing regime of whisker formation is determined by inhibitors concentration and supersaturation. Designing (macro)molecules controlling crystallization is an essential approach to regulate structure and properties of crystalline materials and circumvent detrimental mineralization in nature, biological, and synthetic systems. Here we discovered four novel, natural polyphenols, including gallic acid, ellagic acid, punicalagin, and tannic acid, as a new class of inhibitors for nucleation and crystal growth of calcium oxalate (CaOx), a primary constitution of kidney stones. Study of time-resolved growth reveals that polyphenols regulate the kinetics of crystal-liquid interface acting as a dual role of growth promoter and inhibitor which displays a new record of growth promotion up to 75% or complete suppression, dependent upon the modifier concentration. Time-elapsed in situ atomic force microscopy measurements unveil these modifiers regulate the growth mode from spiral-mediated to generation of two-dimensional (2D) islands and layer spreading mechanism, leading to formation of step bunches growing out of (0 1 0) surface and forming macroscopically crystal whiskers. The governing regime between growth promotion and inhibition is determined by inhibitors concentration but can be influenced by crystallization driving force. Such unique growth mechanism of crystal whiskers may also provide potential implications for understanding and synthesizing branched and hierarchical structures of biomimetic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A serials of BiOCl crystals with various surface oxygen vacancies (OVs) were prepared by one-step solvothermal method. • The enriched surface OVs can induce efficient charge separation, whole visible-light absorption, and photo-thermal effect. • The bandgap and electronic structure of BiOCl ware adjusted by OVS. • The OVs abundant BiOCl nanosheets show an excellent selective CO production rate of 15.33 μmol·g−1·h−1. A simple and controllable solvothermal method was used to synthesis a series of BiOCl nanosheets with various surface oxygen vacancies (OVs) concentration. The introduction of OVs on surface BiOCl nanosheets broaden the photo-absorption to the visible-light-region, induce a remarkable photothermal effect, and enormously promote efficient charge separation. The OVs abundant BiOCl nanosheets exhibit an outstanding selective CO generation rate of 15.33 μmol·g−1·h−1 under the simulated sunlight irradiation, without any sacrificing regent, which is roughly 20.1 times higher than that of pure BiOCl nanosheets. For the degradation of Rhodamine B and tetracycline hydrochloride under visible light, the activity of OVs enriched BiOCl nanosheets is about 43 and 19.5 times higher than that of pure BiOCl nanosheets. The improved photocatalytic activity is attributed to the strong photothermal effect, the tuned electronic structure and the excellent visible light absorption induced by oxygen vacancies. Furthermore, the possible photocatalytic mechanisms, including the separation and transport of carriers, generation process of reactive species and degradation intermediates of tetracycline hydrochloride, are revealed in-depth. Hence, this work may pave the way to illustrate the function of oxygen vacancies in the semiconductor photocatalysis process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ni-doped WO 3 nanorod films were fabricated by reactive magnetron co-sputtering with GLAD technique. • GIXRD investigation revealed crystalline of annealed Ni-doped WO 3 nanorod film at 500 °C. • The local structural transformation was studied by a combination of XAS and DFT calculation. • Annealed Ni doped WO 3 nanorod photoanode at 400 °C presents an improving. • PEC performance. Ni-doped WO 3 nanorod films were fabricated via a reactive magnetron cosputtering with a glancing angle deposition technique. The crystal structure and surface morphology were observed using grazing incident X-ray diffraction and field emission Scanning Electron Microscopy, respectively. The chemical compositions and oxidation state of each element were investigated by X-ray photoemission spectroscopy. The local structure and phase evolution were investigated via X-ray absorption spectroscopy. The local structure of Ni atoms in WO 3 nanorod films is characterized as a NiWO 4 nanocluster in the WO 3 matrix, which is supported by calculated spectra. The phase information obtained after annealing demonstrates that short-length order in amorphous transitions to crystallinity. The phase information of the local structures were acquired and discussed as well as the effect on the annealing process. The coupling of amorphous WO 3 , crystalline WO 3 , and amorphous NiWO 4 exhibits high photoelectrochemical activity of the sample annealed at 400 °C, which was observed with a large current density (2.35 μA/cm2) at 1.20 V vs. Ag/AgCl under visible light irradiation, which is greater than that of the unmodified WO 3 photoelectrode (1.38 μA/cm2). [ABSTRACT FROM AUTHOR]

[Display omitted] • Pb and alkali depletion is shown on the polished surface of lead crystal. • The Pb leaching kinetic is rapidly limited by diffusion through a barrier layer. • In acetic acid, the silanol condensation explains the formation of the barrier layer. • Successive leaching and storage reduce the Pb release from lead crystal glass. Lead crystal glass (24 wt% PbO) is one of the tableware materials that can release lead into the environment. A deep knowledge of the release of lead (Pb) due to food contact is necessary to control and minimize the human exposure to this heavy metal. The Pb leaching was characterized by elemental analysis (ICP-AES) of the 4 vol% acetic acid solution to simulate the food contact versus leaching time. The analysis of the subsurface layer (SIMS, STEM) allows to understand the change of composition and morphology. After an initial period of rapid leaching, the diffusion of lead out of the glass slows down, due to the formation of a blocking barrier of diffusion in the subsurface layer of lead crystal glass. Experiments, carried out with a D 2 18O solution, highlight the different mechanisms of hydrolysis, then condensation of the silanol groups, explaining the decrease of the diffusion coefficient of Pb2+ by the formation of a "passive" sub-layer. This protective sub-layer can be reinforced by successive leaching processes or by the storage of lead crystal glass at high temperature after leaching. [ABSTRACT FROM AUTHOR]

Highlights: [•] Surface polarities of the plate-like and color-zoning cBN crystals are investigated by microscopy, chemical etching, XPS, Raman, etc. [•] The {111}B and faces of cBN crystals can be distinguished by microscopy. [•] {111}B sectors have much higher crystalline quality than sectors. [ABSTRACT FROM AUTHOR]

Abstract: GaS single crystal layers have been thermally treated under argon flow for 4h at two different temperatures (700°C and 900°C). The starting GaS sample and the annealed ones have been characterized by X- ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy. It was found that GaS transformed into β-Ga2O3 through the formation of Ga2S3 intermediate phase. Moreover, such an oxidation process involved the growth of dense Ga2S3 sub-micron crystallites at a temperature of 700°C and relatively long β-Ga2O3 nanowires (up to 4μm) at a temperature of 900°C. Experiments also evidenced that an intentional supply of oxygen was unfavourable both to the formation of Ga2S3 phase and to the growth of sub-micron crystallites and nanowires. [Copyright &y& Elsevier]

[Display omitted] • Sn modification flexibly adjusts the crystal and surface structures of TiO 2. • Well-dispersed rutile TiO 2 film is induced by moderate Sn addition. • Proper Sn into Ru/Ti oxide strengthens structure robustness and catalytic activity. • Abundant oxygen vacancies on the surface can act as an active oxygen reservoir. • Excessive Sn content renders more crystal disorder and volatile substrate. RuO 2 supported on rutile TiO 2 or SnO 2 has been proved extremely effective for catalyzing the oxidation of HCl into Cl 2. The supports play a crucial role in the catalyst systems. In this work, Ti-Sn oxides with different Sn/(Sn + Ti) molar ratios (0–0.2) were synthesized by a facile co-precipitation method as supports. The corresponding Ru/Ti-Sn oxide catalysts were investigated in HCl catalytic oxidation and systematically characterized to elucidate the role of Ti-Sn oxide supports on the process. The diffraction, spectroscopy and microscopy results reveal the crystal and surface structures of supports and catalysts. Among all the RuO 2 /Ti 1-x Sn x O 2 catalysts, RuO 2 /Ti 0.97 Sn 0.03 O 2 exhibits the best catalytic activity of 2.6 g Cl 2 ·g cat -1·h−1 with only 0.5% Ru loading and excellent stability on stream. Differed from the previous understanding, Ti 0.8 Sn 0.2 O 2 support containing the most rutile phase shows unsatisfying performance. The excessive Sn content renders more crystal disorder and volatile substrate, inevitably lowering the dispersion and stabilization of RuO 2 active phase. However, moderate Sn addition induces well-dispersed SnO 2 and rutile TiO 2 film, facilitating the dispersion of RuO 2 phase on the support surface with more active oxygen species. A large number of oxygen vacancies on Ti 0.97 Sn 0.03 O 2 can act as an active oxygen reservoir and boost catalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D flower-like In 2 O 3 /ZnO composite derived from In 2 O 3 precursor/ZIF-8 is gained. • Composite has flower-like In 2 O 3 /ZnO structure composed of needle-like nanorods. • Sensors show an excellent gas-sensing response of 188.01 to 100 ppm TEA at 120 °C. • Mechanism is mainly due to the accelerated multi-orientation electron transport. • In 2 O 3 -based sensors can be used for actual detecting area of seafood storage. Flower-like In 2 O 3 /ZnO heterostructures consisting of the assembled needle-like nanorods derived from In 2 O 3 precursor/ZIF-8 have been prepared by a two-step approach. Flower-like In 2 O 3 /ZnO structures can be achieved by adjusting the nucleation competition and crystal surface matching of In 2 O 3 and ZnO, leading to the enhancement of gas adsorption on the surface, chemical reaction kinetics, and the electron transport efficiency. In/Zn-2 sensors exhibit excellent gas-sensing response value of 188.01 to 100 ppm triethylamine at 120 °C as well as good gas selectivity, long-term stability, and linear relationship compared with pure In 2 O 3 , mainly attributed to the accelerated multi-orientation electron transport mechanism within flower-like In 2 O 3 /ZnO heterostructures. In addition, In/Zn-2 samples can be utilized to detect the practical triethylamine gas released during the storage of marine organism (fishes). [ABSTRACT FROM AUTHOR]

[Display omitted] • The catalytic activity and structure of LSFCr and LCFCr electrodes were investigated. • The investigation was carried out as a function of cathodic polarization history. • Polarized LSFCr electrodes showed obvious surface Sr segregation and deactivation. • Polarized LCFCr electrodes showed negligible surface Ca segregation and deactivation. • The disparate behaviors of the two electrodes were related to an A-site size effect. Surface alkaline-earth segregation is a common problem encountered for the cathodes of solid oxide fuels cells based on perovskites (ABO 3) containing alkaline-earth acceptor dopants. In this work, the porous electrodes of La 0.3 Me 0.7 Fe 0.7 Cr 0.3 O 3−δ (Me = Sr, Ca) were employed as the model specimens to look into the surface segregation issue. The two electrodes were cathodically polarized by continuously testing their cathodic current polarization curves. The electrocatalytic activity of the two electrodes was examined in relation with their cathodic polarization history. Moreover, the crystal and surface structures of the cathodically polarized electrodes were analyzed. An appreciable segregation of strontium onto the surface was detected for cathodically polarized La 0.3 Sr 0.7 Fe 0.7 Cr 0.3 O 3−δ electrode, leading to an obvious deceleration of disassociative adsorption of molecular oxygen on the surface and thus degradation of the electrode activity. In contrast, La 0.3 Ca 0.7 Fe 0.7 Cr 0.3 O 3−δ electrode displayed nearly negligible surface calcium segregation and degradation of the electrocatalytic activity after experiencing an identical cathodic polarization history. The disparity of the two electrodes was related to their A-site compositions. This work exemplifies the importance of minimizing A-site cation size mismatch in stabilizing the crystal structure of the perovskite electrodes under cathodic polarization conditions and therefore alleviating the segregation of A-site alkaline-earth cations onto the electrode surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • The correlation of NO chemisorption with its dissociation pathways. • The effective activation energies of the possible NO dissociation pathways. • NO prefers to be adsorbed on β-MnO 2 (1 1 0) instead of (1 0 1) surface. MnO 2 -based oxide catalysts have recently drawn so much attention owing to its good catalytic activity for NOx direct catalytic decomposition at low-temperature. As the reaction mechanism of NO direct catalytic decomposition on different MnO 2 surfaces is not yet clear, it is important to understand the influence of different crystal surfaces of β-MnO 2 on catalytic activity for NO decomposition. The correlation of NO chemisorption with its dissociation pathways on β-MnO 2 (1 1 0) and (1 0 1) surfaces are investigated based on density functional theory (DFT) with Vienna Ab-initio Simulation Package (VASP). The calculation results have shown that NO prefers to be adsorbed on β-MnO 2 (1 1 0) instead of β-MnO 2 (1 0 1) surface. The analysis results of density of states and differential charge density indicate that the interaction between NO and β-MnO 2 (1 1 0) surface is stronger and the adsorbed NO had more charge transfer with β-MnO 2 (1 1 0) surface. The effective activation energies of the possible NO dissociation pathways on the β-MnO 2 (1 1 0) and (1 0 1) surfaces are 2.57 and 3.07 eV, respectively. The lower energy barrier on β-MnO 2 (1 1 0) must be associated with the bridge adsorption of NO and more electrons transfer from NO to the surface, which is conducive to the breaking of N - O bond. [ABSTRACT FROM AUTHOR]

Abstract: XPS and UPS investigations of ultrathin films of In/Ag and Ag/In, deposited onto the W(110) surface in the ultrahigh vacuum conditions have been performed. Indium and silver films were formed by “in-situ” evaporation on W(110) substrate. XPS and UPS studies have been performed by means of SCIENTA ESCA200 instrument. The changes of In4d core-level and Ag4d valence band emissions with increasing Ag and In coverage were monitored to observe the energy shift and shape of the spin–orbit doublet of In4d and Ag4d lines in the Ag/In/W and In/Ag/W systems. UPS (HeI and HeII) measurements were supported by XPS AlKα measurements of In3d and W4p levels, as well as by investigations of Ag3d levels. XPS and UPS data allowed to evaluate the coverage and make conclusions concerning intermixing and surface alloying in the In/Ag/W and Ag/In/W systems. W(110) substrate can be cleaned after each deposition by thermal desorption and no alloying in the In/W and Ag/W systems is observed. [Copyright &y& Elsevier]

In this work, we synthesized accurately the three spinel Co 3 O 4 samples with different exposed crystal planes, and the methane oxidation activities following an order of Co 3 O 4 -(2 2 0) > Co 3 O 4 -(3 1 1) > Co 3 O 4 -(1 1 1). The mutual transformation of Co3+ Oh and Co2+ Oh is considered as the source of activity, and surface adsorbed oxygen is activated to reactive oxygen species react with methane. Highly reactive oxygen species play an important role in the reaction process. The (2 2 0) crystal surfaces exhibit the highest methane catalytic activity because of the high exposure of Co3+ and surface lattice oxygen atoms. [Display omitted] • Co 3 O 4 nanowires showed higher performance for oxidations of methane. • Co 3 O 4 nanowires mainly expose (2 2 0) crystal planes. • The (2 2 0) crystal planes expose more Co3+ and surface lattice oxygen atoms. • The mutual transformation of Co3+ Oh and Co2+ Oh is the source of activity. • Surface adsorbed oxygen species are induced to convert into reactive oxygen. Identifying the activity origin of spinel Co 3 O 4 catalysts is extremely important for fundamental research and practical application. It is reported that octahedrally coordinated Co3+ (Co3+ Oh) is considered as active sites in spinel Co 3 O 4 , but there is still a lack of sufficient evidence to prove the effect of Co species. In this work, we synthesized accurately the three spinel Co 3 O 4 samples with different exposed crystal planes to investigate the reaction mechanism between methane molecule and Co species. The activity results show that methane oxidation activities follow an order of Co 3 O 4 -(2 2 0) > Co 3 O 4 -(3 1 1) > Co 3 O 4 -(1 1 1). A series of in-situ characterization analyses are performed to explore the evolution process of Co species and the transform of lattice oxygen species for methane combustion. The results indicate that the high catalytic activity is assigned to the exposed state of surface lattice oxygen atoms and the mutual transformation of Co3+ Oh and Co2+ Oh. Therefore, it explained that the high activity of the (2 2 0) crystal plane is mainly involved with the high exposure of Co3+ and surface lattice oxygen. Adsorption oxygen species were induced to reactive oxygen species during the transformation of Co3+ Oh stable structure and Co2+ Oh unstable structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Concepts for evolution the morphology of supersmooth surfaces of oxide single crystals. • Transformation of a supersmooth crystal surface begins at the Tamman temperature. • The step height on vicinal (0001) faces is either equal to c /6 or multiple of this value. • Annealing of a (0001) cleavage face of LaMgAl 11 O 19 leads to the formation of prisms. Evolution of the α-Al 2 O 3 , La 3 Ga 5 SiO 14 , and LaMgAl 11 O 19 single crystals supersmooth surfaces at annealing in air was investigated using thermodynamic calculations. In particular the characteristic temperatures and annealing ranges were calculated when the surface melting phenomena took place or atomically smooth steps were formed and moved due to the surface diffusion processes. Later conclusion was confirmed in the surface probe microscopy experiments with regard to the crystal structure data of α-Al 2 O 3 , La 3 Ga 5 SiO 14 , and LaMgAl 11 O 19 , specifically the surface diffusion processes dominated at comparably low annealing temperatures (less than surface melting temperature T sm). In this temperature range the crystal structure near the surface was rather stable, that is why one could assume the electrically neutral clusters of Al 2 O 3 , LaMgAl 11 O 19 и La 3 Ga 5 SiO 14 involved in the surface diffusion processes instead of single atoms. A further increase in annealing temperature to T sm resulted in the La 3 Ga 5 SiO 14 crystal surface thermodestruction due to probably incongruent melting of La 3 Ga 5 SiO 14 compound and related friability of its structure if to compare it with Al 2 O 3 and LaMgAl 11 O 19 structures with the layers of close-packed oxygen atoms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel NO interaction with the SiO x /TiO 2 (1 1 0)-(1 × 2) system. • Full XPS, UPS, AES characterization. • Charazterization of dissociative adsorption via Freundlich isotherm. The interaction of nitrogen monoxide (NO) with 0.8 monolayer of silicon, deposited onto rutile single crystal surface SiO x /TiO 2 (1 1 0)-(1 × 2), has been studied by means of X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS), and Auger electron spectroscopy (AES), in order to characterize the interaction of NO, up to 200 langmuir at room temperature, with the SiO x /TiO 2 interface. This interaction resulted in the oxidation of titanium species, as well as a weak reduction of silicon species. Furthermore, adsorbed nitrogen is not detected on the surface. These results suggest that the adsorption is dissociative, characterized by a Freundlich isotherm. [ABSTRACT FROM AUTHOR]

• AAO dual-bandgap heterostructure photonic crystals are made by periodic voltage–time waveform. • Ag@AAO DHPCs synergistically enhance the local electric field strength. • The introduction of multiple PBGs in SPR absorption range of Ag nanoparticles further enhances Raman signal. • Ag@AAO DHPC SERS substrate enhancement factor reaches 106, detection limit 10−11 mol/L. Photonic crystals (PCs) are regarded as ideal materials for surface-enhanced Raman scattering (SERS) active substrates due to their unique optical behaviors of photonic band gap (PBG). In this work, for the sake of introduction of more PBGs in visible range, the Ag nanoparticle loaded anodic aluminum oxide dual-bandgap heterostructure photonic crystals (Ag@AAO DHPCs) SERS-active substrates are fabricated by using a specially designed periodic voltage–time waveform and vacuum thermal evaporation technology, which have a large-scale highly ordered nanopore structure, tunable high-quality multiple PBGs. As SERS substrates, the Ag@AAO DHPCs show excellent SERS-activity for Rhodamine B (RhB) with ultra-high sensitivity, uniformity, stability and reproducibility, the calculated enhancement factor (EF) can reach as high as 1.3 × 106, and the concentration limit can fall to an ultra-low value of 10−11 mol/L, suggesting that the trace detection of RhB could be realized with them. The outstanding SERS-activity of the Ag@AAO DHPCs would be mainly attributed to the introduction of multiple PBGs in surface plasma resonance (SPR) absorption range of silver nanoparticles and matching with the incident light, therefore, the stronger surface local electromagnetic field is obtained to enhance the SERS-activity through the synergistic effect of the Bragg reflection and the slow photon effect at the PBGs' edges of AAO DHPCs. The Ag@AAO DHPC SERS-activity substrates are beneficial to the explorations of enhancement mechanism of surface Raman scattering signals and the developments of Raman imaging, biomolecular detection and chemical analysis. [ABSTRACT FROM AUTHOR]

• ZnO pyramidal structures are attainable under an oxygen deficient environment. • Surface-stabilized chemical vapor deposition can grow high-index crystal surface. • The surface property was studied by water splitting and electrostatic potential. • Pyramidal ZnO surface shows ambipolar semiconducting properties. • Photocatalytic performances are improved by 73% on the pyramidal surfaces. While the low-index planes of Wurtzite ZnO, such as { 0001 } and { 10 1 ¯ 0 } are well-understood, the high-index crystal surfaces have not yet been thoroughly researched despite possessing structural characteristics that make them suitable for many important surface chemistry processes. The high surface energy of high-index ZnO crystal surfaces makes synthesis challenging to achieve due to their instability during crystal growth. In this work, we present a combined experimental and theoretical analysis of growth and photocatalytic activity of ZnO high-index crystal facets. Density functional theory calculations are performed to determine the thermodynamic conditions necessary to stabilize the high-energy semi-polar { 11 2 ¯ 2 } facets of pyramidal ZnO nanostructures grown via chemical vapor deposition (CVD). The photocatalytic properties of as-synthesized nanopyramidal structures for water splitting applications showed a 73% improved photocatalytic performance compared to CVD-grown hexagonal ZnO nanorods with dominating low-index { 10 1 ¯ 0 } facets. [ABSTRACT FROM AUTHOR]

• Ternary heterojunctions possesses the effective separation of charge pairs. • Bi 2 S 3 /MoO 3 /C 3 N 4 heterojunctions exhibit remarkable stability. • The excellent photocatalytic activity has been obtained. • Bi 2 S 3 /MoO 3 /C 3 N 4 is double S-scheme heterojunctions. In this article, double S-scheme Bi 2 S 3 /MoO 3 /C 3 N 4 heterojunctions with excellent photocatalytic performance were fabricated via a facile one-pot solid-state reaction. The structural and morphological analysis of the as-prepared heterojunctions was implemented to understand the crystal structure and surface properties. The results of photocatalytic experiments exhibit that Bi 2 S 3 /MoO 3 /C 3 N 4 heterojunctions prepared by 11.5 g thiourea, 0.1333 g ammonium molybdate tetrahydrate and 0.02 g bismuth(III) citrate display the highest activity under solar light irradiation, the activity of which is seven times of that of C 3 N 4 , and nearly three times of that of MoO 3 /C 3 N 4. The ameliorated performance originates from the construction of double S-scheme heterojunctions which possesses the effective charge pairs partition and migration. The cycling experiments display that Bi 2 S 3 /MoO 3 /C 3 N 4 heterojunctions exhibit remarkable stability. In the light of the radical trapping experiments, nitroblue tetrazolium (NBT) experiments, electron spin resonance (ESR), and the match of energy band, double S-scheme mechanism was proposed. This work also provided a new facile solid-state reaction method to synthesize double S-scheme heterojunctions with high performance for efficient abatement of pollutants. [ABSTRACT FROM AUTHOR]

• Non-periodic Pt vacancy defects are characteristic of graphene/Pt(111) system. • A novel method for synthesis of nano-thin Pt 5 Gd alloy underneath a graphene. • The alloy surface is terminated by Pt atomic layer with "kagome" structure. • Stoichiometric composition of the alloy can be used to control the graphene doping. In the present study we synthesized nano-thin epitaxial Pt x Gd alloys on Pt(111) single crystal surface covered with well-oriented graphene and investigated their electronic and atomic structure at different stages of synthesis. Low-energy electron diffraction, photoelectron spectroscopy and scanning tunneling microscopy data suggest that deposition of Gd on the graphene/Pt(111) system and its further intercalation at 1080 ° C lead to formation of nano-thin Pt 5 Gd alloy covered with a quasi-freestanding graphene. We demonstrate that atomically flat alloy surface is terminated by Pt atomic layer with "kagome" structure. Control of graphene doping through variation of the alloy stoichiometry may open up new opportunities in developing advanced electronics. Owing to a well-known catalytic activity of Pt 5 Gd alloy, our thin-film system is promising for low-cost production of catalysts in the near future. [ABSTRACT FROM AUTHOR]

• Molten KOH etching have been first applied to polishing sliced SiC. • Sa roughness is reduced from 246.5 nm to 16.06 nm within 2 min of molten KOH etching. • A damage-free surface can be obtained. • Etching behaviors and mechanisms for dislocation spot is particularly studied. Single-crystal silicon carbide (4H-SiC) is a promising third-generation semiconductor material because of its excellent electrical, mechanical and chemical properties. However, the high hardness of 4H-SiC makes it a typical difficult-to-machine material, which greatly restricts the development of SiC devices. In this work, molten KOH etching was first used to polish SiC. The perfect crystal surface and dislocation spots were studied separately. For the perfect crystal surface, a typical isotropic etching polishing behavior was observed. The speed of the polishing process was closely correlated with the temperature. An ultrafast polishing of sliced SiC was achieved, reducing the roughness from 246.5 nm to 16.06 nm within 2 min at 800 °C, and all subsurface damage was removed, as demonstrated by TEM. For the dislocation spot, a relationship between the etch pits angle and temperature was found, making it possible to remove the influence of the dislocation spot by increasing the etch pits angle to approach 180°. This study shows that molten KOH etching could be a very promising SiC polishing method and deserves further research. We anticipate that this approach will be applicable to ultrafast polishing of SiC at the industrial scale. [ABSTRACT FROM AUTHOR]

A nonpolar molecule paraffin grows into 2-D crystal on the surface of polar substrate mica by the PVD-based heteroepitaxial mode. Inside the 3-fold symmetric nanopatterns, paraffin molecules adopt vertical orientations and crystallize into either monolayer or multilayered structures, which depends on both the evaporating temperature and deposition time. • A novel PVD-based heteroepitaxial crystallization method has been built on the air–solid interface. • By adopting a perpendicular orientation to mica surface, paraffin can epitaxially grow into 3-fold symmetric crystal-based nanostructures with different dimensions. Inspired by the crystallization/fibrillization of proteins/peptides on the liquid–solid interfaces, here we demonstrate a novel approach to create low dimensional crystals of nonpolar organic molecules on polar inorganic substrates by the heteroepitaxial growth means on the air–solid interface. Using physical evaporation deposition (PVD) on air–solid interfaces, paraffin as a model nonpolar molecule can epitaxially grow into patterned crystal nanostructures on a polar substrate mica (001). With the atomic force microscopy and the small angle diffraction of synchrotron radiation X-ray, we figure out that the hydrocarbon chain of paraffin is perpendicular to the atomic lattice of mica, and the heteroepitaxial growth is originated from a large tolerance of the distance matching between the adjacent silicon atoms on the surface of mica and the adjacent paraffin terminals inside its crystal nanostructure. This study cannot only fill up the gap for researching the heteroepitaxial crystallization of nonpolar organic molecules on polar inorganic substrates, but also demonstrates that the approach reported in this work holds potential for creating low-dimensional molecular crystals, nanopatterns and functional nanofilms. [ABSTRACT FROM AUTHOR]

Z-scheme 0D/2D Ag 6 Si 2 O 7 /CN photocatalyst was designed to take the advantage of the high stability of CN and the full-spectral photoresponses of Ag 6 Si 2 O 7. It is confirmed that CN can act as an electron acceptor in ACN-15 to promote the separation of photogenerated electron-holes, enhance the reduction ability of photogenerated electrons, ameliorate the photocatalytic instability of Ag 6 Si 2 O 7 and improve the photocatalytic performance under full-spectrum irradiation. • A direct Z-scheme 0D/2D Ag 6 Si 2 O 7 /CN photocatalyst was fabricated for the first time. • The composite exhibits superior photocatalytic activity under full-spectrum light. • The CN can collect photoelectrons and inhibit the photocorrosion of Ag 6 Si 2 O 7. • Electronic and optical properties of Ag 6 Si 2 O 7 and CN are reported. Herein, we reported a Z-scheme 0D/2D Ag 6 Si 2 O 7 /CN composite photocatalyst via simple precipitation method, where the electron structure and optical properties of Ag 6 Si 2 O 7 and CN materials were studied by theoretical computation. The XPS, TEM, radical trapping experiments and ESR measurement results illustrated the formation of the Z-scheme 0D/2D Ag 6 Si 2 O 7 /CN heterostructure. The crystal structure and surface composition of the prepared materials were characterized by XRD, SEM and FT-IR. The UV–vis DRS, PL, I-t, and EIS demonstrated that all composites have improved light absorption ability and enhanced photo-generated charge separation rate. The construction of 0D/2D Ag 6 Si 2 O 7 /CN Z-scheme heterojunction is helpful to improve photodegradation ability, which can not only enhance the separation and transmission efficiency of the photogenerated carriers, but also retain the strong redox ability of photocatalysts. This paper provides a novel comprehension of the mechanism of Z-scheme composites by combining theoretical calculations and experiments. [ABSTRACT FROM AUTHOR]

• Metallic-semiconducting Ta 3 B 2 @Ta 2 O 5 heterostructure with enhanced photocatalytic activity have been prepared by in-situ solid state reaction. • There is about 80% of methylene blue (MB) being photodegraded over Ta 3 B 2 @Ta 2 O 5 and it is about two times higher than that of pure Ta 2 O 5 commercial powder. • The double metallic layers of interface and Ta 3 B 2 nanodots contribute the enhanced photocatalytic activity of Ta 3 B 2 @Ta 2 O 5 heterostructure. Metallic-semiconducting Ta 3 B 2 @Ta 2 O 5 heterostructure with enhanced photocatalytic activity have been prepared by in-situ solid state reaction, using Ta 2 O 5 and NaBH 4 powders. As-prepared Ta 3 B 2 @Ta 2 O 5 products were characterized by XRD, FESEM, HRTEM, EDS, XPS and UV–vis absorption. The results showed that (2 1 0) crystal surface of Ta 3 B 2 have tightly combined with (0 0 1) crystal surface of Ta 2 O 5 to form a core-hell heterostructure. From the photocatalytic activity test, there is about 80% of methylene blue (MB) being photodegraded in 180 min over Ta 3 B 2 @Ta 2 O 5 , which is about two times higher than that of pure Ta 2 O 5 commercial powder ~38%. It is worthy pointing out that the enhanced photocatalytic activities originate from the metallic layer of interface and Ta 3 B 2 nanodots. This special construction could accelerate electron mobility, increase visible light harvesting and enhance electron-hole separation ratio. Therefore, the Ta 3 B 2 @Ta 2 O 5 heterostructure as a promising photocatalyst should have potential applications in removal of environmental pollution. [ABSTRACT FROM AUTHOR]

• C 3 N 4 /MoO 3 composite was successfully developed via wet chemical technique. • 20 wt% MoO 3 in C 3 N 4 /MoO 3 composite expedite the best photocatalytic efficiency. • Charge separation is via z-scheme formation enhancing the catalytic activity. • Photogenerated holes and superoxide radicals are the main reactive oxide species. • CNMO-20 exhibits stable catalytic performance for four experimental cycles. The photocatalysis has been well recognized in the photodegradation of toxic contaminants in water. The heterojunction of various semiconductors is widely used to improve photocatalytic properties compared to the single-component system. In this work, we prepared a heterojunction based photocatalyst using a wet-chemical technique consisting of pyrolysed porous C 3 N 4 and hydrothermally synthesized MoO 3 nanobelt like structure for enhanced photocatalytic oxidation of rhodamine B under visible light irradiation. The developed microcomposite was well characterized for its structural and morphological analysis to understand the crystal structure and surface properties. The increase in catalytic activity with C 3 N 4 /MoO 3 microcomposite is attributed to the efficient photogeneration of electron-hole pairs, and charge transfer due to favorable band positions of C 3 N 4 /MoO 3 , which is not possible with individual materials. Radical trapping experiments were conducted with the microcomposite to confirm the major participating species in the photochemical reaction and the cyclic experiments were also carried out for stability of the designed composite for the photochemical process. This work also emphasizes the development of heterojunction microcomposite for environmental remediation. [ABSTRACT FROM AUTHOR]

• Residues might exist in a smooth surface acquired from polishing treatments. • Surface etching methods to remove the residues for different GaN planes are proposed. • AFM help identify the type of crystal surface of GaN. Surface etching methods were investigated for the removal of residues of chemical reagents and contaminants from polar (Ga- and N-plane), semipolar (r-plane) and nonpolar (a- and m-plane) freestanding GaN surfaces. Ga-, N-, r- and m-plane were etched in H 3 PO 4 , NaOH and (NH 4) 2 S solutions. A-plane was treated in the solution of 10 wt% KOH in ethylene glycol (EG) at 80 °C. Different surface morphology were obtained and were characterized with atomic force microscope. The typical characteristics for the surface morphologies and interfacial angles in each etched GaN plane may help identify the type of crystal plane conveniently. Ga-polar GaN shows a clear and uniform step structure on surfaces. N-plane presented a step structure with tooth-like terraces. The (2 0 2 ¯ 1) r-plane, m-plane and a-plane show stripe-like structures, while the (2 0 2 ¯ 1 ¯ ) r-plane is stable and hard to be etched to exhibit step structures. The m-plane facets on a-plane surface caused by the etching method was found and discussed. [ABSTRACT FROM AUTHOR]

• Two types of gold nanoclusters are formed on annealing Au/GaAs structures. • The clusters are either buried in GaAs or located just on crystal surface. • The local plasmons of the Au clusters occur at 1.6 and 2.15 eV, respectively. A procedure is developed for controlled creation of Au nanoclusters by annealing of a gold film deposited onto GaAs(0 0 1) crystal surface. The nanoclusters of Au are formed at GaAs surfaces covered by either a natural oxide layer or a monolayer of gallium nitride. Surface morphology of the Au/GaAs structures with Au nanoclusters is characterized by scanning probe diagnostics and localized plasmons of the nanoclusters are investigated by optical reflection spectroscopy. In annealing Au film dissimilar gold nanoclusters are found to occur on oxidized or nitridized GaAs(0 0 1) surface via chemical transformation or recrystallization of Au film, respectively. Gold nanoclusters of the two types cause resonant peaks in optical reflectance spectra at the energies of 1.6 eV and 2.15 eV. Using the data of optical spectroscopy and their theoretical analysis we assign the former peak to localized plasmons of prolate Au nanoclusters buried into GaAs crystal near its surface. Another peak at 2.15 eV is attributed to plasmons of oblate Au nanoislands appearing on nitride overlayer which prevents any chemical contact of Au with GaAs bulk. The asserted existence of Au nanoclusters in the bulk of GaAs crystal near its oxidized surface is expected to be helpful in elucidating the nature and structure of Ohmic Au-GaAs contacts. [ABSTRACT FROM AUTHOR]