Bias Voltage Dependence of the Electrical and Optical Properties of ZnO:Al Films Deposited on PET Substrates

In this research, ZnO:Al thin films were deposited on polyethylene terephthalate (PET) substrates by using the capacitively coupled r. f. magnetron sputtering method from a ZnO target mixed with 2 wt% Al2O3. The effects of substrate bias on the electrical properties and the film structure were studied. Films deposited with positive bias had a strong (002) preferred orientation. The electrical resistivity of the film decreases significantly as the positive bias was increased up to +30 V. However, as the positive bias increased above +30 V, the resistivity decreased. The transmittance varied little as the substrate bias was increased from 0 to +60 V, and as the r. f. power was increased from 160 W to 240 W. An electrical resistivity as low as 1.8 x 10(-3) Omega-cm and an optical transmittance of 87.8 % were obtained for a 1012 nm thick film deposited at a substrate bias of +30 V.