Raman And Impedance Characteristic Of Colloidal MoS₂ Under Pressure

This work is mainly for Raman and impedance characteristics of MoS₂ at high pressure. The Impedance spectrum of MoS₂ at high pressure was obtained through 400 Thigh-pressure setup and home-made impedance analyzer, and the result indicates that the magnitude of impedance decreases with increasing pressure. The shift of Raman peaks of MoS₂ at high pressure was obtained by using diamond anvil cell (DAC) equipment, this experiment result shows that the Raman peaks shift to higher wavenumber at high pressure, but the relative intensity of Raman peaks decreases with increasing pressure, and the full width at half maximum (FWHM) of Raman peaks increases with increasing pressure.In the introduction, the development history of high pressure physics and common measuring method at high pressure are introduced, especially the measurement of impedance and Raman spectrum at high pressure. High pressure Raman spectrum is mainly used to monitor the structure transition of materials at high pressure.The second chapter introduces the history of 400-T high-pressure machine, repair, debugging, pressure calibration and application. The history of the 400-T high-pressure machine is introduced at first, secondly the principles of hydraulic pressure system and controlling circuit of high-pressure machine are described. And then the detailed stepping up, stepping down and pressure calibration processes are given. At last the impedance of MoS₂ at high pressure was obtained.The third chapter mainly describes the impedance measurement based on the discrete Fourier transform(DFT) and the design, manufacture and calibration of impedance analyzer based on AD5933 chip. The home-made impedance analyzer may take the place of commercial analyzer and measure the impedance at high pressure.The fourth chapter introduces the Raman spectrum of MoS₂ at high pressure. Raman spectra of colloidal MoS₂ with the average diameter of 4 μ m at high pressure were obtained. The experiment result indicates that the Raman peaks shift to higher wavenumber with increasing pressure, but the relative intensity of Raman peaks decrease with increasing pressure, and the FWHM of Raman peaks increases with increasing pressure. The Gruneisen constants: 0.28 and 0.61 for mode E_2g¹ and A_1g, respectively, were obtained through the fitting of the experiment data.