Growth conditions for pulsed laser deposited FeTeO$_{y}$ superconducting thin films and observation of a low temperature structural transition

FeTe thin films were grown by pulsed laser deposition and oxygen was incorporated to make superconducting FeTeO$_{y}$. The Te concentration of the films was highly dependent on growth temperature, due to the evaporation of Te at higher temperatures. Films grown using a porous, unreacted Fe/Te target showed islanding, an open structure, and a strong c axis texture. Oxygen could be easily added or removed by low temperature anneals. Films grown using a dense, polycrystalline conglomerate for a target and a short target-substrate distance had better epitaxy, and were dense, continuous and smooth. Post processing of oxygen on these films was difficult, but we were able to control oxygen concentration during growth using a small oxygen partial pressure. Initial low temperature diffraction studies of these films using both x-rays and neutrons indicate a sudden change in c axis lattice parameter at the superconducting T$_{C}$, but continued exposure of the beam drives out oxygen. Dense epitaxial films should allow for studying this phase change.