Randomly oriented Angstrom-scale microroughness at the Si(100)/SiO2 interface probed by optical second harmonic generation

Femtosecond pulses from a Kerr–Lens mode-locked Ti:sapphire laser are used to generate second harmonic from a series of native-oxidized Si(100)/SiO2 and hydrogen-terminated Si(100) samples prepared with systematically varied interfacial microroughness with root-mean-square feature heights ranging from 0.6 to 4.3 Å. Rotationally anisotropic second harmonic signals using different polarization configurations were measured in air and correlated with atomic force microscopy measurements. The results demonstrate rapid, noncontact, noninvasive measurement of Angstrom-level Si(100)/SiO2 interface roughness by optical second harmonic generation.