Structural, optical, and dielectric properties of Cr-doped ZnO films via DC magnetron sputtering

TL;DR

This study introduces a new method for fabricating Cr-doped ZnO films via DC magnetron sputtering and annealing, revealing how Cr doping affects microstructure, optical, and dielectric properties, with potential applications in transparent electrodes.

Contribution

The paper presents a novel annealing-based fabrication method for Cr-doped ZnO films and analyzes their properties, demonstrating improvements in transmittance, conductivity, and stability.

Findings

Grain size decreases with Cr doping

Band gap increases with Cr doping

High transmittance and conductivity at optimal Cr levels

Abstract

Cr-doped ZnO films were fabricated by a new but feasible method, that is, annealing Cr-Zn layers deposited via DC magnetron sputtering in air. Microstructures of the films were investigated using X-ray diffraction, scanning electron microscopy, and atomic force microscopy, intrinsic point defects were identified via photoluminescence spectroscopy, and optical and dielectric properties were analyzed using a UV-vis spectrophotometer and dielectric spectrometer, respectively. It was found that the average grain sizes decrease (56.34 - 39.50 nm), the band gap increases (from 3.18 to 3.23 eV), and the transmittance (at 600 nm) decreases (from 91% to 83%) with increasing Cr. Two activation energies of conduction increase after doping Cr, indicating enhanced temperature stability. At optimal Cr levels, ZnO films exhibit high transmittance and conductivity, exhibiting potential for transparent electrode development. This method can be extended to other doped ZnO films, such as Al-doped ZnO transparent electrodes, to achieve simultaneous improvements in transmittance, conductivity, and stability for flexible and wearable applications.