Dielectric function spectra and critical-point energies of Cu2ZnSnSe4 from 0.5 to 9.0 eV

Authors

S. . G. Choi, National Renewable Energy Laboratory, Golden, Colorado
H. . Y. Zhao, Royal Institute of Technology
C. Persson, University of Oslo
C. L. Perkins, University of Oslo
A Donohue, J.A. Woollam Co. Inc., Lincoln, Nebraska
B To, National Renewable Energy Laboratory, Golden, Colorado
A. G. Norman, National Renewable Energy Laboratory, Golden, Colorado
J Li, National Renewable Energy Laboratory, Golden, Colorado
I. L. Repins, National Renewable Energy Laboratory, Golden, Colorado

Date of this Version

2012

Citation

JOURNAL OF APPLIED PHYSICS 111, 033506 (2012);

doi:

10.1063/1.3681814

Abstract

We present dielectric function e=e₁+ie₂spectra and critical-point energies of Cu₂ZnSnSe₄ determined by spectroscopic ellipsometry from 0.5 to 9.0 eV. We reduce artifacts from surface overlayers to the maximum extent possible by performing chemical-mechanical polishing and wet-chemical etching of the surface of a Cu₂ZnSnSe₄ thin film. Ellipsometric data are analyzed by the multilayer model and the e spectra are extracted. The data exhibit numerous spectral features associated with critical points, whose energies are obtained by fitting standard lineshapes to second energy derivatives of the data. The experimental results are in good agreement with the e spectra calculated within the GW quasi-particle approximation, and possible origins of the pronounced critical-point structures are identified.