Influence of the RF magnetron sputtering power on the optical and electrical properties of AZO films

Abstract

Thin AZO films were synthesized using radio frequency magnetron sputtering method on the surface of polished silicon samples and glass slides. The sputtering power was varied in the range of 150–300 W with the step of 25W; deposition time was adjusted so that the film thickness remained equal to 70 nm. The rest of the deposition parameters: working pressure, temperature, and the substrate rotation rate, remained unchanged. The thickness and deposition rate of thin films were measured using X-ray reflectometry. The electrical properties (resistivity, Hall mobility and charge concentration) of thin films were measured by the Van Der Pauw method using the Hall effect. The transmission spectra of the films were measured in the wavelength range from 300 to 1100 nm. The average crystallite size was determined using X-ray diffraction spectra and the Scherrer equation. As a result, it was shown that AZO films synthesized at a power of 300 W have the best electrical and optical properties. At this power, the lowest resistivity value of 2.83×10^-3 Ω∙cm and the maximum charge mobility of 9.6 cm²V^-1sec^-1 were achieved for films of the same thickness 70 nm. The decrease in the electrical resistivity of the films with increasing power is explained by more intense heating of the substrate during deposition, which leads to an improvement in the crystallinity of the film, and, as a consequence, to an increase in the mobility of charge carriers.