I present a method for the use of second-harmonic generation (SHG) as a means to probe the buried interface between Si(001) and SiO2. I begin with a brief retelling of the history of SHG and its development into a powerful technique to study the material properties of centrosymmetric media and interfaces due to its unique dependence on a material’s symmetry. The theory behind SHG is explored along with the relation between the second-order susceptibility tensor and crystal point group symmetries. I show it is possible to separate the surface and bulk contributions to the signal by the use of rotational-anisotropy SHG (RA-SHG) and polarization selection techniques. Speciﬁcally, the symmetry properties of Si(001) and the Si(001)/SiO2 interface are explored and a phenomenological theory predicting the intensity proﬁle of the SHG signal is described. A method for recovering the Fourier ﬁt coeﬃcients that describe the susceptibility tensor is demonstrated and experimental implications discussed. The data presented demonstrates the eﬀectiveness of SHG as a tool to study the symmetry properties and surface/interface behavior of a substance.
Bevis, Charles, "Optical Second Harmonic Generation in the Si(001)/SiO2 Interface" (2011). Undergraduate Honors Theses. 27.