Characterization Of 3C-SiC And 3C-SiC Nanowires Grown By LPCVD

As the third generation semiconductor material,3C-SiC has many excellent properties.Such as wide band gap,high critical breakdown electric field,high electron saturation drift velocity,high thermal conductivity and so on.However,the large lattice mismatch and thermal expansion coefficient make the epitaxial film more difficult.In this paper,3C-SiC was grown on Si substrate by low pressure chemical vapor deposition(LPCVD)method.The effects of the process parameters(growth temperature,growth pressure,growth time and C/Si ratio)on the surface morphology and crystallization quality were studied.The growth of 3C-SiC was analyzed by different material analysis methods.The characteristics of 3C-SiC nanowires were studied.The results are as follows.1.The 3C-SiC prepared on the Si substrate by LPCVD method is a polycrystalline structure with the preferred orientation of 3C-SiC(111)orientation.2.Comparing with different growth temperatures.It is concluded that with the increase of growth temperature,The 3C-SiC surface and cross-sectional morphology indicate that a film has been grown,but the surface is uneven and holes appear.Less holes when reaching 1300 ℃When the growth temperature reaches 1350℃.the surface of the epitaxial layer becomes rough.So 1300℃ is a better growth temperature.3.Comparing with different growth pressures.It is concluded that as the growth pressure increases.The surface roughness of 3C-SiC decreased and crystallinity increased under 104Pa.So 104Pa is a better growth pressure.4.Comparing with different growth time.It is concluded that the growth time was prolonged,under the condition of 120 min,the epitaxial layer is more uniform with fewer holes.The surface growth rate is obviously improved.Therefore,120 min is a better growth time.5.Comparing with different C/Si ratio,the growth pattern of a single nucleus gradually develops from vertical to lateral growth as the C/Si ratio increases.Nanowires appear when the C/Si ratio is 1.4.When the C/Si ratio is kept at 1.8,the epitaxial layer is relatively uniform,with fewer holes and the crystal quality is improved.VSM test shows the 3C-SiC is magnetic,XPS test shows no metal.Therefore,1.8 is a better growth ratio of C/Si.6.The grown nanowires are typical 3 C-SiC poly crystalline structures.High-density irregularly disordered nanowires appear on the surface of the sample.About 400-500nm in length and approxim 20 nm in diameter.It was believed that since the grately growth of 3C-SiC nanowires took place during the the heating-up and dwelling processes rather than cooling process.Through the variable temperature VSM,the coercive force,residual magnetization and saturation magnetic field strength of 3C-SiC nanowires decrease with increasing temperature.The luminescence peak at 442 nm was obtained by PL,and there was a clear blue shift with respect to the bandgap width of 3C-SiC.It is concluded that 3C-SiC magnetism is due to the formation of a compound that reacts with Fe or from vacancies.