Effects of annealing on structure, resistivity and transmittance of Ga doped ZnO films

Abstract

Effects of annealing on the electrical resistivity and transmittance properties of Ga doped ZnO (GZO) thin films deposited on glass by radio frequency (RF) magnetron sputtering were investigated. The electrical resistivity of a GZO thin film is effectively decreased by annealing in a reducing atmosphere such as N 2 z5%H 2 . This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. However, annealing at a temperature .400uC is less effective. The lowest resistivity of 2 . 3610 24 V cm is obtained by annealing at 400uC in an N 2 z5%H 2 atmosphere. The optical transmittance of the GZO film is improved by annealing regardless of the annealing atmosphere. Annealing in an N 2 z5%H 2 atmosphere widens the optical band gap, while annealing in an O 2 atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.

Effects of Ar vs. O2 ambient on pulsed-laser-deposited Ga-doped ZnO

“…To achieve the high conductivity required for transparent conductive oxides (TCOs), Ga-doped ZnO films are often annealed in forming gas (5-10% H 2 /balance Ar or N 2 ) [1,2]. This improvement in conductivity has been attributed to the passivation of acceptors by H donors and the improved transport across the grain boundaries [3][4][5].…”

Highly conductive ZnO grown by pulsed laser deposition in pure Ar

“…© 2010 American Institute of Physics. ͓doi:10.1063/1.3481372͔ Forming-gas ͑FG͒ ͑5% H 2 in Ar͒ annealing of ZnO films doped with donor impurities such as Al, Ga, or In, has been shown to increase conductivity 1,2 and is often used in preparing transparent conductive oxides ͑TCOs͒. The improved conductivity has often been attributed to the ability of H to directly provide donors and also to passivate negatively charged acceptors, including those causing potential barriers in grain boundaries.…”

Influence of Substrate Temperature and Post-Deposition Annealing on Material Properties of Ga-Doped ZnO Prepared by Pulsed Laser Deposition

“…Indeed, thermal desorption spectrometry of Zn with mass fragment 64 has shown that rapid evaporation of Zn atoms from Ga-doped ZnO surfaces occurs in vacuum at temperatures exceeding 300°C. 18 It has been reported that the energy barrier for self-diffusion of intrinsic defects in ZnO is lowest for Zn +2 interstitials, 31 32,33 To validate these speculations about the concentration of gallium as a function of deposition temperature, SIMS analysis was carried out on as-deposited Ga-doped ZnO, as shown in Fig. 9.…”