Optical and electrical properties of doped zinc oxide films prepared by ac reactive magnetron sputtering

Abstract

Aluminum-doped and indium-doped zinc oxide films have been prepared by reactive ac magnetron sputtering (twin-cathode arrangement with ac plasma excitation at frequency of 40 kHz) from metallic targets with different dopant concentrations at substrate temperature of about 573 K. The optical, electrical and structural properties of the sputtered ZnO:Al and ZnO:In thin films have been investigated by optical spectroscopy (UV-IR), X-ray diffraction, Hall-mobility and conductivity measurements. For aluminum-doped ZnO films a minimum resistivity of 4.0 × 10 −4 Ω cm at high transparency (larger than 89% at film thickness of 530 nm) has been obtained at Al concentration in the target material of 1.2 wt%. Higher resistivity of 8.7 × 10 −4 Ω cm (85% transmission at film thickness of 400 nm) has been observed for indium-doped zinc oxide films at dopant concentration of about 2 wt% In in the target material.