A spectroscopic anisotropy ellipsometry study of YBa 2Cu 3O 7− x superconductors

Abstract

The effect of the optical anisotropy of the high temperature superconducting compound YBa 2Cu 3O 7− x (YBCO) on spectroscopic ellipsometry (SE) measurements was studied. For this, the method of spectroscopic anisotropy micro-ellipsometry (SAME) was employed on c-axis- as well as on a,b-axes-oriented YBCO single crystals. SAME measures the ellipsometric parameters Δ and Ψ as a function of the angle α which describes sample rotation around the surface normal. The analysis of the resulting Δ(α) and Ψ(α)-curves yielded the ordinary and averaged extraordinary complex refractive indices in the UV-VIS range. Additionally, the crystallographic orientation angle ϕ between the optical axis and the surface normal could be determined. The single crystal results were applied to SE measurements performed on differently oriented YBCO thin films which were prepared by ion beam sputter deposition on top of (100) SrTiO 3 substrates. It is shown that SE allows for in-situ monitoring of the crystallographic orientation of thin YBCO films.