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We report water-induced nanometer-thin crystalline indium praseodymium oxide (In-Pr-O) thin-film transistors (TFTs) for the first time. This aqueous route enables the formation of dense ultrathin (~6 nm) In-Pr-O thin films with near-atomic smoothness (~0.2 nm). The role of Pr doping is investigated by a battery of experimental techniques. It is revealed that as the Pr doping ratio increases from 0 to 10%, the oxygen vacancy-related defects could be greatly suppressed, leading to the improvement of TFT device characteristics and durability. The optimized In-Pr-O TFT demonstrates state-of-the-art electrical performance with mobility of 17.03 ± 1.19 cm2/Vs and on/off current ratio of ~106 based on Si/SiO2 substrate. This achievement is due to the low electronegativity and standard electrode potential of Pr, the high bond strength of Pr-O, same bixbyite structure of Pr2O3 and In2O3, and In-Pr-O channel's nanometer-thin and ultrasmooth nature. Therefore, the designed In-Pr-O channel holds great promise for next-generation transistors. [ABSTRACT FROM AUTHOR]

GaSe is an important member of the post-transition-metal chalcogenide family and is an emerging two-dimensional (2D) semiconductor material. Because it is a van der Waals material, it can be fabricated into atomic-scale ultrathin films, making it suitable for the preparation of compact, heterostructure devices. In addition, GaSe possesses unusual optical and electronic properties, such as a shift from an indirect-bandgap single-layer film to a direct-bandgap bulk material, rare intrinsic p-type conduction, and nonlinear optical behaviors. These properties make GaSe an appealing candidate for the fabrication of field-effect transistors, photodetectors, and photovoltaics. However, the wafer-scale production of pure GaSe single-crystal thin films remains challenging. This study develops an approach for the direct growth of nanometer-thick GaSe films on GaAs substrates by using molecular beam epitaxy. It yields smooth thin GaSe films with a rare γ'-polymorph. We analyze the formation mechanism of γ'-GaSe using density-functional theory and speculate that it is stabilized by Ga vacancies since the formation enthalpy of γ'-GaSe tends to become lower than that of other polymorphs when the Ga vacancy concentration increases. Finally, we investigate the growth conditions of GaSe, providing valuable insights for exploring 2D/three-dimensional (3D) quasi-van der Waals epitaxial growth.

We report water-induced nanometer-thin crystalline indium praseodymium oxide (In-Pr-O) thin-film transistors (TFTs) for the first time. This aqueous route enables the formation of dense ultrathin (~6 nm) In-Pr-O thin films with near-atomic smoothness (~0.2 nm). The role of Pr doping is investigated by a battery of experimental techniques. It is revealed that as the Pr doping ratio increases from 0 to 10%, the oxygen vacancy-related defects could be greatly suppressed, leading to the improvement of TFT device characteristics and durability. The optimized In-Pr-O TFT demonstrates state-of-the-art electrical performance with mobility of 17.03 ± 1.19 cm2/Vs and on/off current ratio of ~106 based on Si/SiO2 substrate. This achievement is due to the low electronegativity and standard electrode potential of Pr, the high bond strength of Pr-O, same bixbyite structure of Pr2O3 and In2O3, and In-Pr-O channel’s nanometer-thin and ultrasmooth nature. Therefore, the designed In-Pr-O channel holds great promise for next-generation transistors.

Abstract: Tribological performance of sub-nano to nanometer-thick Ag layers deposited on Si(111) have been examined to understand the effect of surface thin layers to the wear and friction characteristics. The slider was made of diamond sphere of 3mm in diameter. Sliding tests were carried out in an ultra-high vacuum environment (lower than 2×10−8 Pa) and analyzed in situ by Auger electron spectroscopy (AES) for the quantitative thickness-measurements, by reflection high-energy electron diffraction (RHEED) to clarify the substrate cleanliness and crystallography of the Ag films, and by scanning probe microscopy (SPM) for the morphology of the deposited/slid film surfaces. The Ag and substrate surfaces were atomically clean during the tribological tests so that the chemical effect of the Ag and Si surfaces appeared directly on the friction and wear processes. Experimental results of the sliding tests indicated that the minimum coefficient of friction (μ) was 0.007 for the 1–5nm thick as-deposited films of Ag on a Si(111) surface. Beyond the minimum thickness region, μ increased to 0.01 or higher. Observations of the slid surfaces showed that the Ag(111) sliding planes orientate parallel to the sliding direction, although the surface morphology of the deposited surface was totally deformed by the slider on the track. The Ag crystallites were not, therefore, destructed crystallographically by sliding but the fine Ag(111) sliding sheets were rotated, sheared, and displaced layer by layer, to orientate the Ag(111) plane parallel to the sliding direction by the reciprocal movement of the slider. After 100 cycles of the reciprocal movements, no worn particles were found around the sliding track and the low friction sliding lasted over 1000 cycles of the reciprocal sliding. The observed results indicated that the atomic force between surface atoms, especially diamond Cal bond, Ag(111) interlayer bonding force, and also the orientation of the sliding planes strongly reflect to the friction force, in addition to the asperity of the surface. A sliding mechanism of very thin layers of Ag film of very low wear and friction is discussed. [Copyright &y& Elsevier]