Influence of substrate temperature and oxygen/argon flow ratio on the electrical and optical properties of Ga‐doped ZnO thin films prepared by rf magnetron sputtering

Abstract

Effects of substrate temperature and atmosphere on the electrical and optical properties of Ga-doped ZnO thin films deposited by rf magnetron sputtering were investigated. The electrical resistivity of Ga-doped ZnO (GZO) films decreases as the substrate temperature increases from room temperature to 300°C. A minimum resistivity of 3.3 x 10 -4 Ω cm is obtained at 300°C and then the resistivity increases with a further increase in the substrate temperature to 400°C. This change in resistivity with the substrate temperature is related to the crystallinity of the GZO film. The resistivity nearly does not change with the O 2 /Ar flow ratio, R for R < 0.25 but increases rapidly with R for R > 0.25. This change in resistivity with R is also related to crystallinity. The crystallinity is enhanced as R increases, but if the oxygen partial pressure is higher than a certain level (R = 0.25 ± 0.10) gallium oxides precipitate at grain boundaries, which decrease both carrier concentration and mobility. Optical transmittance increases as R increases for R < 0.75. This change in transmittance with R is related to changes in oxygen vacancy concentration and surface roughness with R.

Effects of substrate temperature on the properties of heavy Ga-doped ZnO transparent conductive film by RF magnetron sputtering

“…With increasing substrate temperature, the diffusion of sputtering species is enhanced and the grains become bigger. However, there is a significant increase in FWHM and grain size becomes smaller when the substrate temperature exceeds 250 ℃; the result is similar to those of literatures [11,12,18]. This fact implies the substrate temperature have a remarkable effect on the structure of ZnO, therefore, high crystalline ZnO films required optimum substrate temperature.…”

“…Secondly, Ga is more resistive to oxidation compared to Al. The third is that it makes less diffusion-related problems since the diffusivity of Ga is lower than that of Al at the same temperature [11]. In spite of these advantages, GZO has been relativity less studied than AZO.…”

Effect of the thickness and hydrogen treatment on the properties of Ga-doped ZnO transparent conductive films

“…Currently, indium tin oxide (ITO) is the representative TCO material due to its high transmittance of about 80% in visible range and low resistivity of about 1 Â 10 À4 V cm [3,4]. However, fast growing display industries and resulting shortage of the expensive indium resources have stimulated efforts to find alternative TCO materials to substitute for ITOs [5].…”

Effects of H2 ambient annealing in fully 002-textured ZnO:Ga thin films grown on glass substrates using RF magnetron co-sputter deposition

“…3(b)] in the first instance. Further, for the samples initially prepared at RT and 373 K, postannealing treatment at 623 K could have contributed to the improvement in crystalline quality and to the activation of the dopant Ga. At the same time, as known, the hydrogen annealing ambient could have passivated the negatively charged oxygen species in the grain boundaries and the surfaces which act as carrier traps [27].…”