Effect of oxygen partial pressure on the structure and properties of Cu–Al–O thin films

We have studied the electrical and optical properties of Cu–Al–O films deposited on silicon and quartz substrates by using radio frequency (RF) magnetron sputtering method under varied oxygen partial pressure PO. The results indicate that PO plays a critical role in the final phase constitution and microstructure of the films, and thus affects the electrical resistivity and optical transmittance significantly. The electrical resistivity increases with the increase of PO from 2.4 × 10−4 mbar to 7.5 × 10−4 mbar and afterwards it decreases with further increasing PO up to 1.7 × 10−3 mbar. The optical transmittance in visible region increases with the increase of PO and obtains the maximum of 65% when PO is 1.7 × 10−3 mbar. The corresponding direct band gap is 3.45 eV.