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Advanced materials: chemical vapor deposition growth of a novel two-dimensional atomic crystal pdse2 with high mobility and optical anisotropy

wallpapers Cruise 2020-12-10
Compared with traditional bulk semiconductor materials

two-dimensional materials have nanoscale thickness novel physical properties which have become one of the research hotspots in the field of low dimensional Optoelectronics in recent years. The most common crystal building units in two-dimensional materials are hexagonal such as graphene molybdenum disulfide (MoS2) etc. Palladium diselenide (pdse2) is a group 10 transition noble metal chalcogenide (ntmdcs) with unique structure. It has rich crystal structure. The most stable structure is the layered orthorhombic phase structure of pentagonal building units. Each layer presents periodic fold shape the interlayer is combined by van der Waals force. Different from the general hexagonal two-dimensional materials pdse2 has strong interlayer interaction intralayer anisotropy resulting in ultra-high carrier mobility thickness adjustable b gap width (0 EV monolayer – 1.3 EV) Due to its excellent environmental stability anisotropic optical properties field effect transistors photodetectors other fields have important application prospects. Although the unique crystal structure abundant phase structure of

bring many possible application prospects to 2D pdse2 how to grow large area high quality 2D pdse2 crystal materials under control is still an urgent problem to be solved. At present most of the research work of two-dimensional pdse2 is based on the mechanical stripping method but the stripping ability of this method is limited which causes inevitable defects to the products especially single-layer materials so it is almost impossible to get large-scale practical application. Therefore finding a bottom-up growth method has become an important challenge.

two-dimensional orthorhombic pdse2 single crystal nanosheets were prepared by chemical vapor deposition (CVD) on a variety of substrates (SiO2 / Si sapphire mica gold foil). The thickness of the nanosheets is as thin as two molecular layers. The morphology thickness of the nanosheets depend on the growth temperature. Professor Ding Feng of Korea Institute of basic science has simulated the CVD growth process of two-dimensional pdse2 by using the dynamic Woolf configuration based on density functional theory. There is a high nucleation barrier along the edge of [110] [- 110] direction so the growth rate is slow. This explains the morphology of square pdse2 nanosheets obtained in the experiment. The optical anisotropy nonlinear optical properties of two-dimensional pdse2 were studied by using angle resolved Raman spectroscopy second harmonic imaging (SHG). The results show that the two-dimensional pdse2 with odd even layers have different central symmetries belong to different point groups space groups. Finally the electron mobility of the annealed pdse2 FET is ~ 294 cm2v-1s-1 the switching ratio is ~ 103 which proves that the crystal quality of pdse2 prepared by this method is close to that of the mechanical stripping method (~ 216 cm2v-1s-1). Researchers believe that by further improving the growth process 2D pdse2 crystals heterojunctions with various phase structures can be prepared thus promoting the application of 2D pdse2 crystals in optoelectronic devices topological superconductivity quantum information science. The related work of

was funded by the US Department of energy the nano center of Oak Ridge National Laboratory was completed by Gu Yiyi during his visit to Oak Ridge National Laboratory with the support of the national scholarship committee.

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