Structural, optical and electrical properties of Hf-doped ZnO transparent conducting films prepared by sol–gel method

Abstract

Hafnium doped zinc oxide (HZO) thin films with various Hf contents (0, 1, 3, 5, 7at.%) at different solution concentrations (0.15–0.75mol/L) were deposited on the glass substrates using sol–gel method. The structural, optical and electrical properties were investigated by means of XRD, PL and Hall-effect measurement. The results show that Hf ions could substitute Zn ions effectively and improve the crystallinity of ZnO significantly with highly preferred c-axis orientation. Based on photoluminescence and transmittance measurements, the strong ultraviolet emission band exhibits a blue shift and its intensity is found to rise with the increasing of Hf-doping density. Furthermore, the resistivity shows a bell curve and the minimum value is 5.6×10−3Ωcm for the HZO film with 3at.% Hf, which is lower than that of the typical Al-doped ZnO thin films using sol–gel method.