The innovation engine for new materials

Sangsoo Kim


University of California, Santa Barbara



Site Abroad: 

Trinity College Dublin, Ireland


Karsten Fleischer

Faculty Sponsor(s): 

Igor Shvets

Faculty Sponsor's Department: 


Project Title: 

Temperature dependent anisotropic changes in SrTiO3 (110)

Project Description: 

Oxygen vacancies are well known for affecting physical properties of SrTiO3 (STO). It is hypothesized that oxygen vacancies can alter the surface anisotropy of STO 110. Using Reflectance Anisotropic Spectroscopy (RAS), we measured STO 110 surface anisotropy between the energy levels of 1.6eV to 5.5eV. Annealing the STO at various temperatures created increasing amounts of oxygen vacancies. Annealing was done in vacuum at 2e-8 mbar pressure with a silicon strip calibrated for current versus temperature. The samples original stoichiometry was recovered by annealing the STO in the atmosphere. The RAS spectra of the STO 110 crystal are presented at each annealing temperature. We show that oxygen vacancies reveal small, trackable changes in RAS; however, larger changes in RAS due to exposing the STO to the atmosphere make oxygen vacancies a miniscule contribution. We additionally try to measure the surface magnetization of STO, but we find the instrumental limit hides any detectable magnetic signals. Correction polynomials are measured and calculated to numerically remove effect of the window’s strain on the RAS spectrum.