Reconstruction and energetics of the polar (112) and(1¯1¯2¯)versus the nonpolar (220) surfaces ofCuInSe2

Abstract

First-principles total-energy calculation reveals a number of (112) and $(1\ifmmode\bar\else\textasciimacron\fi{}1\ifmmode\bar\else\textasciimacron\fi{}2\ifmmode\bar\else\textasciimacron\fi{})$ surface structures stable at different atomic chemical potentials. All of the stable structures are charge compensated, thus semiconducting, either by cation-on-cation antisites, cation vacancies, Se adatoms, or by Se addimers. This structural richness raises the possibility for engineering ${\mathrm{CuInSe}}_{2}/\mathrm{Cu}({\mathrm{In}}_{1\ensuremath{-}x}{\mathrm{Ga}}_{x}){\mathrm{Se}}_{2}$ material properties by surface control during the growth. The experimentally observed puzzling spontaneous decomposition of the (220)/(204) surfaces into (112) and $(1\ifmmode\bar\else\textasciimacron\fi{}1\ifmmode\bar\else\textasciimacron\fi{}2\ifmmode\bar\else\textasciimacron\fi{})$ is also confirmed by calculating individual surface energies.