Stacking fault and unoccupied densities of state dependence of electromagnetic wave absorption in SiC nanowires

Abstract

Understanding the relationship between the defects and properties could give the guidance to tailor the materials by virtue of regulating defects. In the present research, β-SiC nanowires (NWs) with different states of stacking faults have been fabricated by varying the heating temperature. The stacking fault states are characterized by transmission electron microscope and powder X-ray diffractometer. The electronic structures are investigated by X-ray absorption near-edge structures (XANES) at C K-edge and Si K-edge. Microstructural analysis revealed that the content of stacking faults in SiC NWs decreased significantly with an increase of heating temperature. The unoccupied density of states (DOS) in the C K-edge XANES spectra positively correlated with stacking fault contents in SiC NWs. The stacking fault planes were inclined at an angle of 35° to the growth direction at a heating temperature of 1400 °C, which were converted to perpendicular to the growth direction as the temperature increased to 1600 °C. The inclined stacking fault planes in the domain induced strongest dielectric resonance. The SiC NWs synthesized at 1400 °C with the highest carbon unoccupied DOS possess the most stacking fault content and numerous dipoles, which result in extensive polarization and energy dissipation under an altering electromagnetic field. As a result, a lowest reflection loss (R_L) value of −30 dB and an effective absorption band (R_L < −10 dB) covering a frequency range of 3.7 GHz were achieved.