Toward Amorphous CuI‐Alloys Deposited by Magnetron Cosputtering: Structural and Microstructural Investigations

Two different solid solutions of CuI, namely, I and Mo x Cu 1– x I, have been deposited via reactive magnetron cosputtering to investigate the suppression of the zincblende γ‐CuI phase by the introduction of foreign atoms into the lattice. A comprehensive growth study is presented, in which sputtering in inert and reactive atmospheres (Ar + I 2 , Ar, N 2 + I 2 , N 2 ) is performed from metallic Cu, Sn, and Mo targets as well as from a CuI powder target. A strong influence of the iodine partial pressure during the deposition on the crystal quality of thin films is observed by X‐ray diffraction measurements. For optimized growth conditions, X‐ray amorphous thin films are achieved for solid solution Sn x Cu 1– x I and Mo x Cu 1– x I thin films deposited from the CuI powder target in an inert Ar atmosphere. However, a microstructural analysis of these thin films by transmission electron microscopy combined with energy‐dispersive X‐ray diffraction spectroscopy and selected area diffraction reveals a phase separation into Sn and O rich, (Mo and O rich, respectively) amorphous regions, and CuI crystallites. Oxygen concentrations between ≈10 at% and ≈70 at%, detected in the thin films, give reason to the assumption of an oxygen induced phase separation.