Transparent conductive aluminum-zinc oxide layers deposited by high pressure sputtering

Abstract

High-pressure sputtering (HPS) is an unconventional method used to deposit various materials, including transparent conductive oxides. This article sets out to investigate aluminum-doped zinc oxide (AZO), a material widely used in solar cells. The aim of this work is to examine the properties of AZO films deposited by HPS and evaluate this method as a viable alternative to conventional deposition techniques. To characterize the films, techniques such as grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) were used to analyze their structure, composition, and surface morphology. Optical characterization showed high transparency in the visible range and optical band gap (Eg) values between 3.41 and 3.60 eV. Additionally, electrical properties were evaluated using the Hall effect and van der Pauw method measurements, revealing resistivities in the range of 5 & sdot;10- 3 Omega & sdot;cm. A direct correlation was observed between the increase in deposition pressure and the carrier concentration. We found that this increase in carrier concentration causes the observed rise in the band gap value, as a result of the Burstein-Moss effect. The results indicate that pressures in the 1.0-1.4 mbar range produce smooth films with high optical transparency and low electrical resistivity, associated with a high carrier concentration. However, at higher pressures (2.2 mbar) the films exhibit greater roughness and a decrease in carrier mobility, despite the increase in carrier concentration. The highest value of Haacke's figure of merit was obtained for the sample deposited at 1.4 mbar. The results obtained demonstrate that AZO deposited by HPS exhibits properties comparable to those obtained by other deposition methods, establishing it as a scalable and cost-effective alternative for next-generation solar cells.