Layer-dependent optical and dielectric properties of centimeter-scale PdSe2 films grown by chemical vapor deposition

Palladium diselenide (PdSe2), a new type of two-dimensional noble metal dihalides (NMDCs), has received widespread attention for its excellent electrical and optoelectronic properties. Herein, high-quality continuous centimeter-scale PdSe2 films with layers in the range of 3L–15L were grown using Chemical Vapor Deposition (CVD) method. The absorption spectra and DFT calculations revealed that the bandgap of the PdSe2 films decreased with the increasing number of layers, which is due to the enhancement of orbital hybridization. Spectroscopic ellipsometry (SE) analysis shows that PdSe2 has significant layer-dependent optical and dielectric properties. This is mainly due to the unique strong exciton effect of the thin PdSe2 film in the UV band. In particular, the effect of temperature on the optical properties of PdSe2 films was also observed, and the thermo-optical coefficients of PdSe2 films with the different number of layers were calculated. This study provides fundamental guidance for the fabrication and optimization of PdSe2-based optoelectronic devices.

Free and self-trapped exciton emission in perovskite CsPbBr3 microcrystals

A broad STE emission band together with a FE emission was found at low temperature in a CsPbBr3 microcrystal sample prepared by CVD method.

Исследование влияния содержания водорода на проводимость нанокристаллических алмазных пленок

The results are presented for investigation of electrical conductivity of nanocrystalline diamond (NCD) films with thickness of 0.5-0.6 microns grown on silicon Si(100) substrate by CVD method using methane-hydrogen and methane-hydrogen-oxygen mixtures. By method of heating in vacuum with use of hydrogen analyzer AB-1 the concentration of hydrogen in the studied films was determined and the relationship between the content of hydrogen in the NCD film and its conductivity was estimated. It was shown that high-temperature processing in vacuum at temperature 6000 C leads to desorbtion of hydrogen from the films and a significant increase in their resistance.

Investigation in double layer graphene superlattice and its electronic properties

This paper mainly discussed the graphene and other 2D materials, as well as their electronic properties. The history and theory prediction of graphene, and production of graphene (mechanical exfoliation and CVD method) are discussed. Graphene hBN superlattice and bi-layer graphene superlattice are presented, with following discussion of the superconductivity of the magic angle. Finally, characterization methods such as AFM and SEM are presented.

The Influence of Pd and Zr Co-Doping on the Microstructure and Oxidation Resistance of Aluminide Coatings on the CMSX-4 Nickel Superalloy

Pd + Zr co-doped aluminide coatings were deposited on the CMSX-4 nickel superalloy, widely used in the aircraft industry, in order to investigate their microstructure and improvement of oxidation resistance. Palladium was deposited by the electrochemical method, whereas zirconium and aluminum by the chemical vapor deposition (CVD) method. Coatings consist of two zones: the additive and the interdiffusion one. The additive zone contains β–(Ni,Pd)Al phase with some zirconium-rich precipitates close to the coating’s surface, whereas the interdiffusion zone consists of the same β–(Ni,Pd)Al phase with inclusions of refractory elements that diffused from the substrate, so called topologically closed-packed phases. Palladium dissolves in the β–NiAl phase and β–(Ni,Pd)Al phase is being formed. Pd + Zr co-doping improved the oxidation resistance of analysed coatings better than Pd mono-doping. Mechanisms responsible for this phenomenon and the synergistic effect of palladium and zirconium are discussed.

Analytical Model of the Process of Thermal Barrier Coating by the MO CVD Method

Integral regularities in the growth of 7YSZ thermal barrier coatings during MO CVD (Metal–Organic Chemical Vapor Deposition) are proposed. Within the framework of the model of the reacting boundary layer, the coating deposition process is considered as a process of independent global reactions of diffusion combustion of Zr(dpm)4 and Y(dpm)3 under convection conditions on a permeable surface. The rate of coating growth and the efficiency of using a precursor are analytically evaluated. The correctness of the proposed approach is confirmed by comparison with known experimental data. The considered model can be used to analyze the deposition of coatings from various mixtures of precursors, such as Nd(dpm)3, Hf(dpm)4, and Sm(dpm)3.

The synthesis of ReS2 flakes and its application in photodetectors

ReS2 is attracting much attention because of its stable trion state. This kind of stable trion state arises on account of weak interlayer coupling as well as anisotropic crystal structure. In this research, we have synthesized ReS2 flakes successfully by using chemical vapor deposition (CVD) method. Stable ionic states in hexagonal wafers are observed by photoluminescence spectroscopy (PL). This substance is stable at room temperature. The HRTEM image from the single ReS2 hexagon reveals that the individual hexagon is single crystal. EDS spectroscopy indicates the purity of the synthesized product. We find that the Re and S atoms ratio in pure ReS2 is 1:2. Then we fabricate a photo detector on individual ReS2 flakes and test its performance. We compare the photocurrent in dark current and under a 500 nm incident light for two media (air and 100 ppm H2). Emission current increases from 1.15 μA to 1.67 μA (forward) and from 7.9 μA to 13.8 μA (reverse). Therefore, the ReS2 hexagonal wafer is an ideal choice for stable and reliable room temperature optical gas sensor. And the material can also be used for fast switch.