Oxygen‐Induced Phase Separation in Sputtered Cu–Sn–I–O Thin Films

Amorphous Cu–Sn–I is a promising p-type transparent semiconductor. Therefore, herein, composition and structure of sputtered thin films with varying thickness Sn content are investigated by different electron microscopy techniques, energy-dispersive X-ray spectroscopy, absorption spectroscopy at the Cu, Sn, I K-edge. After exposure to air, found contain significant amounts oxygen, leading complete phase separation resulting Cu–Sn–I–O films. Spatially-resolved compositional analysis high-resolution transmission reveal that one consists crystalline γ-CuI while other composed amorphous Cu–Sn–O, most likely mixture SnO2 Cu2O/CuO. confirms local structural environment atoms similar in CuI, respectively. In contrast, near edge extended fine Cu K-edge both demonstrate not only bonded but also O atoms. The incorporation oxygen into thus completely alters material therefore clearly needs be inhibited.