Optical and Electrical Properties of Magnetron Sputtering Deposited Cu-Al-O Thin Films

摘要

We have successfully prepared Cu-Al-O films on silicon (100) and quartz substrates with copper and aluminum composite target by using radio frequency (RF) magnetron sputtering method. We have related the structural and optical-electrical properties of the films to the sputtering area ratio of Cu/Al for the target (τ_(Cu/Al))- The deposition rate of the film and τ_(Cu/al) can be fitted by an exponential function. τ_(Cu/Al) plays a critical role in the final phase constitution and the preferred growth orientation of the CUAlO_2 phase, thus affecting the film surface morphology significantly. The film with main phase of CuAlO_2 has been obtained with τ_(Cu/al) of 45%. The films show p-type conductivity. With the increase of τ_(Cu/al) the electrical resistivity decreases first and afterwards increases again. With τ_(Cu/al) of 45%, the optimum electrical resistivity of 80 Ω · cm is obtained, with the optical transmittance being 72%-79% in the visible region (400-760 nm). The corresponding direct band gap and indirect band gap are estimated to be 3.6 eV and 1.7 eV, respectively.