Preparation And Properties Of Ni?Al-Doped SiC Films

Silicon carbide?SiC?,as a new one of the typical representatives of the third generations of semiconductors materials,it has excellent thermal conductivity,breakdown electric field and saturation electron drift speed,higher melting point and operating temperature than the first-generation semiconductors represented by Si and second-generation semiconductors represented by GaAs.So SiC has been widely used in the high temperature and high frequency,radiation protection,power devices and many other fields.In this paper,the magnetron sputtering method was used to deposit Si and Ni?or Co,Al?plasma on a pyrolytic graphite substrate to obtain a prepared doped SiC semiconductor film.By changing the area ratio of these doping materials such as Ni,Co and Al,we achieved different doping atomic percentages.The sputtering time is 70 min,so the prepared films have a deposited silicon layer which is about 630 nm.Then the prepared films treated with the annealing treatment,the annealing temperature was 1080°C and the annealing time was about 12 hours,finally they became the crystallized 3C-SiC diluted magnetic semiconductor films.The SiC film was tested and analyzed by the X-ray diffractometer?XRD?,Raman spectrometer,cold field scanning electron microscope?SEM?,EDS spectrometer,vibrating sample magnetometer?VSM?and reflectance spectrometer.In this paper,the effects of different doping concentrations of Ni,Co and Al on the crystal structure,surface morphology,magnetic properties and reflection spectra of SiC films based on pyrolytic graphite substrates were investigated.The Ni doped SiC films with doping Ni atomic percentages of 0.63 at%,1.11 at%,2.03 at%,and 4.37 at%were prepared.With the increase of Ni doping atomic percentage,it was found that the diffraction peaks represent Ni₂Si and NiSi₂ in the X-ray diffraction spectrogram of SiC film,the diffraction peak maximum of the 3C-SiC film is reduced,and the uniformity and continuity of the films are better,and the saturation magnetization and the coercive force of the SiC films are increasing.Compared with the undoped SiC film,the reflectivity of the SiC films doped with Ni is improved in the visible wavelength range?200⁷50 nm?,when doping Ni with a 4.37 at%atomic percentage,the reflectance of the SiC film reaches a maximum about 14%at the wavelength of 600 nm.In the X-ray diffraction spectrograms of Co-doped SiC films appering CoSi?210?diffraction peak and CoSi₂?220?diffraction peak when the Co doped atomic percentage are 4.63at%and 6.48 at%.With the increase of Co doped atomic percentages,the degrees of crystallinity of the 3C-SiC films are worse,but their saturation magnetizations are gradually increased.Observing the X-ray diffraction spectrograms of Al-doped SiC films,almost no other compound phase formation been observed.With the increase of Al-doped atomic percentages,the intensities of the three major peaks of 3C-SiC?111?,?220?and?310?are enhanced,although the growth rates of the enhancement are gradually reduced.And the surfaces of SiC films are more flat,uniform and continous,the saturation magnetizations are increasing with a decreased growth rate.It shows that within a certain range,the increase of the atomic percentage of Al doping will enhances the saturation magnetization of the SiC films,but the gain effect will be weaken along with it.