| High manganese silicon film thermoelectric materials (MnSi1.73) is a metal silicide thermoelectric materials, which can convert waste heat into industrial and residential electricity and has wide application prospect. But now the films prepared by these methods have too many problems because of the heterogeneous reaction, such as scale is insufficient, uneven thickness, and have too much impurity phase. Therefore, we must find a new method which can easily prepared the size, morphology is controlled, and continuous uniform film.In order to prepare a better MnSi1.73film, this project use MnCl2as the Mn source, the Si substrate is heated within the atmosphere of the MnCl2in vacuum conditions, to prepare the MnSi1.73film. By using isothermal contact growth way and the isothermal non-contact way to study high manganese silicon phase formation on the substrate surface and thin film morphology characteristics. Secondly, by studying the relationship between the thickness of the film and growth time under different temperature and time, to determine the best condition to prepare the MnSi1.73is900℃-12h. Finally, we use the thermodynamics and dynamics data to research its growth law.In the experiment, a variety of analysis methods are used. Through the optimization of different process parameters, we obtained a best method to prepare the large scale, morphology controlled, continuous MnSi1.73film and analyzed the phase change and the change law of the interface. The electronic structure was measured by optical properties. The conclusions are following:1、The field on prepare MnSi1.73film(1)、Through researching the film which was prepared in contact way we know that there is no MnSi1.73film was found under500℃and600℃. Under the700℃, by scanning morphology and energy spectrum analysis we find that there is MnSi1.73to generate, but the film is too thin and the content is low. Every temperature region under800℃can determine the MnSi1.73, but the surface of the film contains too much impurities and uneven holes.(2)、The film layer which was clean, single phase, and uniform thickness was prepared in isothermal non-contact way. Compared the surface under different holding time and sintering temperature, it is find that900℃-12h is the condition which can prepare the best film surface. Compared with the film thickness under the same holding time and different sintering temperature, it was found that the film thickness showed a trend of decrease after the first increase. The best process parameters of preparing for HMS thin film is:under the condition of high vacuum, isothermal non-contact growth way,900℃-12h.2、The phase change law of HMS film and spectrum performance(1) TEM analysis indicated that under the condition of850℃for12h, the prepared HMS film along [100] crystal orientation to grow and perpendicular to the surface of the Si substrate. SiO2was generated on some parts of the film. The epitaxial relationships between HMS and Si substrate are:MnSi1.73[100]/Si [111] and MnSi1.73[011]/Si [011].(2) Spectral data analysis shows that the HMS is direct band gap and energy gap is about0.7eV.(3) The forming rule of the HMS film is as follows:The HMS and the phase before shift were generated in500℃. In600℃it all changed to MnSi. And then the SiO2and the small amount of HMS were created in700℃. The SiO2and the HMS were created in800℃. After that, the clean HMS were appeared in900℃. Lastly, the SiO2and HMS were also appeared in1000℃. The thickest film reaches8μm in900℃. The presences of a small amount of SiO2have played an important role to promote growth of the single-phase HMS and restrain the formation of the MnSi. |
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