Improving electrical properties of sol-gel derived zinc oxide thin films by plasma treatment

Abstract

Being a direct and wide bandgap semiconductor, zinc oxide is a suitable material for various optoelectronic applications. These applications require tuning and controlling over the electrical and optical properties of zinc oxide films. In this work, zinc oxide thin films were prepared by a solution method that led to oriented crystal growth along (002) plane. The zinc oxide thin films were treated with oxygen, hydrogen, and nitrogen plasmas. The films were characterized to reveal the effects of plasma treatments on transmittance, crystallinity, carrier density, carrier mobility, and electrical resistivity. Oxygen plasma treatment improved the crystallinity of the zinc oxide thin film without affecting the film's transmittance. Hydrogen plasma treatments were found very effective in improving the electrical conductivity sacrificing the film's transmittance. Nitrogen plasma treatment led to improved electrical conductivity without compromising the crystallinity and optical transmittance. Sequential oxygen, hydrogen, and nitrogen plasma treatments significantly reduced the resistivity of zinc oxide thin films by over two orders and maintained the transmittance close to the as-deposited films of ∼80% in visible wavelength range. This is the first work on the improvement of conductivity of solution-based zinc oxide films using the plasma treatment.