The Preparation And Properties Of Bismuth Selenide Thin Films And Alloy Structures By Physical Vapor Deposition

The alloy structures of thin film based on Bi2Se3, Bi2Te3 and Sb2Te3 is not only the most widely used thermoelectric material, but also the strong topological insulator, so it is possible to be the basic material of Dirac solid state quantum application. In this study, we got the single crystal, ternary and quaternary alloy thin films based on Bi2Se3 and Sb2Te3 in vacuum tube furnace by physical vapor deposition(PVD). Their performance was examined by a series of measurements. The research mainly focuses on the electrical transport properties of the quaternary alloy thin films and the photoelectric properties of ternary alloy thin films. The detailed content and conclusion were described as follows.Firstly, PVD is a useful and simple method to get thin films, we build a system and prepare the Bi2Se3 single crystal thin film, the X-ray diffraction peaks indicated that the c-axis preferred orientation of the film, the SEM image show that there exist triangular spiral domains on the surface, and it indirectly proved its layer structure. The preparation of single thin films provided technical support and comparison for the growth of multi-component alloy thin films.Secondly, we tried to prepare the quaternary alloy thin films(BixSb2-x)( SeyTe3-y) according to the plan we have made. After changing the growth environment and conditions, we successfully got the quaternary alloy thin films at last. Then we systemically studied the structure, surface morphology, composition, electric transport properties and scattering mechanism by X-ray diffraction(XRD), Scanning electron microscope(SEM), X-ray energy dispersive spectroscopy(EDS), Hall effect measurement and Raman spectroscopy. As the increasing value of x and y, the diffraction peak position moved from Sb2Te3 to that of Bi2Se3, the surface roughness became worse, more defects appeared, the carrier concentration decreased, the mobility increased, the peak position of Raman Scattering have a red-shift as a whole. The quaternary alloy thin films have huge potential research value in thermoelectric area.At last, the ternary alloy thin film CaxBi2-xSe3 by doping calcium into Bi2Se3 was got. we found that the main crystal orientation did not change after analyzing its crystal structure and surface morphology. By studying its electric transport properties with Physical property measurement system, we found the carrier conduction type successfully reversed to P-type and the carrier concentration decreased comparing with the Bi2Se3 single thin film, the magnetic resistance curve proved the existence of the weak localization. We measured the transmittance of the ternary alloy thin film in wavelength range of visible light and near-infrared, the increasing linearly transmittance in near-infrared wavelength provided a possibility for the ternary alloy thin film applied in infrared detection.