Study On The Synthesis And Photoelectric Properties Of SiAs Crystals By Chemical Vapor Transport

Since the advent of graphene,people have been interested in two-dimensional crystals similar to graphene in which van der Waals forces stack atomic layers.With the deepening of research,the family of two-dimensional crystals is also growing.Silicon arsenide（SiAs）,as a member of the IVA-VA family of new layered semiconductors,has attracted wide attention from researchers due to its novel p-type semiconductor characteristics.Elemental arsenic（melting point:817℃）has the characteristics of being heated to 613℃ under high pressure and directly sublimated without liquefaction.Therefore,the high-pressure environment is very favorable for the reaction conditions of arsenic compounds;Simultaneously,SiAs is a kind of arsenic-containing compound.For safety reasons,the open growth system cannot meet the requirements of the growth environment for SiAs crystals.However,the CVT system with high-vacuum airtight characteristics meets the requirements for the reaction and growth of SiAs crystals,and as an effective product purification method,the CVT system is also conducive to the growth of high-quality SiAs crystals.In this thesis,the growth of SiAs crystals was realized by CVT method,two-dimensional SiAs crystals were prepared by mechanical peeling,and the properties and photoelectric properties of SiAs crystals were studied.The main research results are as follows:The experimental conditions for the growth of SiAs crystals by CVT method were determined,and the growth of strip SiAs crystals with an average length of about 2 cm（some up to 3-4 cm）was achieved.With the help of XRD,STEM and other characterization methods,it is proved that the SiAs crystal grown by CVT method has good crystalline quality.Furthermore,the molecular vibration modes of SiAs crystals（3.31 nm-15.08 nm）of different thicknesses were further studied by Raman spectroscopy.For the first time,two noticeable redshifts of Raman peak positions were found in the low wavenumber region.With the help of its p-type semiconductor characteristics,the construction of p-n junction devices based on p-type SiAs crystals and the study of optoelectronic properties have been realized for the first time.The results show that the p-type SiAs/n-type SnS₂ multilayer heterojunction exhibits prominent rectification characteristics at a source-drain voltage of-1V to1V,and the ratio of forwarding conduction current to reverse turn-off current is close to 10².Under 550 nm laser irradiation,the light responsivity reaches 1 A/W,significantly better than pure SiAs devices and other IVA-VA family layered semiconductor devices;The p-type SiAs and n-type MoS₂ multilayer heterojunctions also show a rectification ratio close to 10².Under 700 nm laser irradiation,the light-dark current switching will be more stable,and the light-dark current switching ratio will be close to 6.This article further explores the properties of SiAs crystals and supplements the gaps in the research on IVA-VA semiconductors.The preparation of SiAs crystals by the CVT method provides a reference for the growth of IVA-VA group crystals and the high-quality synthesis of other new crystal materials.In addition,our work shows that p-SiAs crystal is a kind of photoelectric material with potential research value and provides experience and help for the further construction of IVA-VA series layered semiconductor p-n junction and other functional devices.