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

Abstract

Thin-films of copper oxide (CuxO) were sputtered from a metallic copper (Cu) target and studied as a function of oxygen partial pressure (OPP). A metallic Cu film with cubic structure obtained from 0% OPP has been transformed to cubic Cu2O phase for the increase in OPP to 9% but then changed to monoclinic CuO phase (for OPP ≥ 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 OPP ranging between 9% and 75% showed p-type behavior, which were successfully applied to produce thin-film transistors.