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Mn+1AXn (MAX) phases are novel structural and functional materials with a layered crystal structure. Their unique properties such as good machinability, high electrical conductivity, low friction, and corrosion resistance are appealing for many engineering applications. Herein, Ti2AlC and Ti3AlC2 MAX thin films are synthesized by magnetron sputtering and subsequent thermal annealing. A multilayer approach is used to deposit single‐element nanolayers of titanium, aluminum, and carbon onto silicon substrates with a double‐layer‐diffusion barrier of SiO2 and SixNy. Ti2AlC and Ti3AlC2 thin films (thickness ≈500 nm) are formed via rapid thermal annealing and verified by X‐Ray diffraction. Nanoindentation tests show hardness values of about 11.6 and 5.3 GPa for Ti2AlC and Ti3AlC2, respectively. The tribological behavior of the Ti2AlC and Ti3AlC2 thin films against AISI 52100 steel balls under dry sliding conditions is studied using ball‐on‐flat tribometry. The resulting coefficient of friction (CoF) for Ti2AlC and Ti3AlC2 ranges between 0.21–0.42 and 0.64–0.91, respectively. The better tribological behavior observed for Ti2AlC thin films is ascribed to its smaller grain size, reduced surface roughness, and higher hardness. [ABSTRACT FROM AUTHOR]

The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm−2 at −1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the native layer at cathodic potentials higher than −1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting. [ABSTRACT FROM AUTHOR]

Polyelectrolyte layer-by-layer assemblies are known as protective coatings for corrosion inhibition. Here, we demonstrate that polyelectrolyte multilayers of poly-(ethyleneimine) (PEI) and poly-(styrene sulfonate) (PSS)(PEI/PSS)xadsorbed at the GaP(100) photocathode surface remarkably mitigate the photocorrosion of GaP without decreasing its photoconversion efficiency. The activity of the polybase–polyacid complex is based on buffering pH changes at the solid–liquid interface. We carried out ab initio molecular dynamics-based simulations of the GaP(100) surface in contact with liquid water and demonstrated that an increase in the proton concentration enhances GaP dissolution. We used the scanning vibrating electrode technique (SVET) to characterize the distribution of photocorrosion activity areas over bare and polyelectrolyte-coated GaP surfaces and we showed that a polyelectrolyte coating impedes the dissolution kinetics. Data obtained using the SVET were compared to photoetched pores on the semiconductor surface. Voltammetric and chronoamperometric measurements were also performed to evaluate photoconversion efficiencies before and after the application of the protective coatings. [ABSTRACT FROM AUTHOR]

Ph y s. 54 (2021) 26960 1 (3pp) ht tps://doi.or g/1 0.1 088/1 361-6463/abef ee Er r at um: Anal y sis of the ph y sical and phot oelectr oc hemical pr oper ties of c-Si(p)/a-SiC:H(p) phot ocathodes f or solar w at er split ting (2021 J. Ph y s. D: Appl. J our nal of Ph y sics D: Applied Ph y sics J. Ph y s. D: Appl. Erratum: Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting (2021 J. Phys. [Extracted from the article]