This work presented results from high-resolution scanning transmission electron microscopy and electron energy-loss spectroscopy on twin boundaries and non-twin grain boundaries in Cu(In,Ga)Se2 thin films. It was shown that the atomic reconstruction was different for different symmetries of the grain boundaries. It was possible to confirm the model proposed by Persson and Zunger (2003) for Se-Se-terminated Σ3 {112} twin boundaries, showing Cu depletion and In enrichment in the two atomic planes closest to the twin boundary. On the other hand, Cu depletion without In enrichment was detected for a cation-Se-terminated twin boundary. At non-twin grain boundaries, always a strong anti-correlation of Cu and In signals was detected suggesting that the formation of InCu or CuIn antisites within a very confined region of smaller than 1nm was an essential element in the reconstruction of these grain boundaries.

Direct Insight into Grain Boundary Reconstruction in Polycrystalline Cu(In,Ga)Se2 with Atomic Resolution. D.Abou-Ras, B.Schaffer, M.Schaffer, S.S.Schmidt, R.Caballero, T.Unold: Physical Review Letters, 2012, 108[7], 075502