Cd₃As₂ Nanostructures: Preparation,Thermoelectric And Optical Properties

At present,Cd₃As₂has been discovered as a new Dirac material,which has great application value in future quantum computers and electron-spin.In recent years,it has become a research hotspot in the field of materials science and condensed matter.With the development of research,it is still difficult to prepare high-quality Cd₃As₂nanostructures.In this paper,Cd₃As₂nanostructures were prepared by chemical vapor deposition（CVD）,and high quality Cd₃As₂nanostructures were obtained by controlling growth temperature,growth time,growth pressure and other factors.Through Mn₃As₂doping,the successful preparation of Cd_3-xMn_xAs₂nanostructures,The influence of different doped Mn₃As₂ratio on the morphological structure,thermoelectric property and optical property of the sample was systematically studied.Scanning electron microscope（SEM）and X-ray diffractometer（XRD）were used to analyze the micro-morphology and growth mechanism of the sample,the thermoelectric property of the sample was tested by The Seebeck coefficient conductivity tester,and the peak and peak position of the sample were measured and analyzed by the Raman spectrometer.The research results are as follows:（1）By chemical vapor deposition method in evaporation source is 650℃,Ar/H₂flow velocity of 20 sccm,furnace tube growth pressure is 0.1 MPa,growth for 10 min,etc under the condition of the preparation of the nanowire diameter of 50nm,length up to 175.6μm,the lattice spacing is 0.73nm,growth direction of[112]direction of high quality Cd₃As₂nanowires and analyzes Cd₃As₂nanowires growth mechanism,electric transport the samples testing and test out the negative magnetic resistance effect of the sample.（2）Cd₃As₂thin film-nanowire structures（The thin film area is covered by a layer of nanowires）and Cd₃As₂nanoscale dendritic structure were prepared at different temperatures,through the characterization of Cd₃As₂nanostructures found that unique sample morphology,nano structure of large size,good crystallinity,and test the samples under different temperature zone in thermoelectric performance of 25-330℃,at room temperature,high temperature of the sample PF value of 0.32 m W m^-1K^-2the low temperature area sample PF value up to 0.005 m W m^-1K^-2,64 times of high power factor is low temperature area.The XRD patterns and Raman spectra of the samples in different temperature zones were tested,and the results showed that the main phase of the samples was Cd₃As₂,belonging to teateristic system core structure,and the Raman peak was basically consistent with the polarization characteristic peak of the crystal structure space group alpha Cd₃As₂（I41cd）.（3）In different atomic ratio 0%;5%;10%proportion of Mn₃As₂preparation for doping Cd_3-xMn_xAs₂nanostructures,found that doping Mn₃As₂can significantly influence the sample morphology structure,crystal orientation and seebeck coefficient,through the study of the thermal performance test of samples of different zones and photovoltaic properties test found that Cd_2.95Mn_0.05As₂optimum properties of nanostructures,and determined to be the best doping ratio.At room temperature,the PF value of the Cd_2.95Mn_0.05As₂nanostructure samples in the high-temperature area was as high as 0.43 m W m^-1K^-2,which was 1.34 times that of the Cd₃As₂nanostructure samples in the high-temperature area,1.48 times that of the Cd_2.9Mn_0.1As₂nanostructure samples,and 47.7 times that of the low-temperature area samples in the same proportion.By comparing the different zones Cd_3-xMn_xAs₂nanostructure samples to XRD spectrum found that samples for main phase Cd₃As₂,doped samples in atomic ratio 5%Cd₃As₂diffraction peak number and peak effect best,test at room temperature under normal pressure Cd_3-xMn_xAs₂Raman spectra in different areas of the nanostructures,found that after doping Mn₃As₂sample preparation by Raman spectrum peak decreases with the increase of Mn₃As₂doping concentration,because after doping Mn₃As₂nanostructures Cd₃As₂atomic placeholder changes,With the increase of Mn₃As₂doping concentration,the crystal lattice constant of the samples becomes smaller,so the Raman peak positions of Cd_3-xMn_xAs₂nanostructure samples all shift to the right.