https://doi.org/10.1063/5.0058962

"Probing the surface potential of SiO2/4H-SiC(0001) by terahertz emission spectroscopy"
Journal of Applied Physics 130, 115305 (2021);
Hidetoshi Nakanishi, Tatsuhiko Nishimura, Iwao Kawayama,Masayoshi Tonouchi, Takuji Hosoi, Takayoshi Shimura, and Heiji Watanabe