p-Type ${\hbox {Cu}}_{x}{\hbox {O}}$ Films Deposited at Room Temperature for Thin-Film Transistors

Thin-films of copper oxide (CuxO) were sputtered from a metallic copper (Cu) target and studied as a function of oxygen partial pressure (O_PP). A metallic Cu film with cubic structure obtained from 0% O_PP has been transformed to cubic Cu₂O phase for the increase in O_PP to 9% but then changed to monoclinic CuO phase (for O_PP ≥ 25%). The variation in crystallite size (calculated from x-ray diffraction data) was further substantiated by the variation in grain size (surface microstructures). The CuxO films produced with O_PP ranging between 9% and 75% showed p-type behavior, which were successfully applied to produce thin-film transistors.