Effects of Annealing in a Partially Reducing Atmosphere on Sputtered Al-Doped ZnO Thin Films

Abstract

Aluminum-doped ZnO (AZO) films have been deposited by room-temperature radio frequency (RF) magnetron sputtering onto fused-quartz substrates using a ZnO:Al 2 O 3 (98:2 wt.%) target. A post-deposition anneal in an N 2 flow has been shown to improve the electrical and optical properties of as-deposited AZO. All films were polycrystalline and exhibited a hexagonal wurtzite structure with the c-axis oriented perpendicular to the substrate. An increase in the estimated crystallite size was observed after annealing. Electrical resistivity was reduced from 3.7 9 10 À3 X cm for as-deposited layers to 7.1 9 10 À4 X cm for annealed films. An average optical transmittance >85% for annealed films was routinely measured. X-ray photoelectron spectroscopy measurements indicated that the surfaces of all layers investigated were oxygen deficient, and the density of oxygen vacancies was found to increase following the anneal.

Wide band-gap investigation of modulated BeZnO layers via photocurrent measurement

“…Here, the I-peak line located at 529.8 eV was attributed to O 2-ions surrounded by four Zn 2? ions in the Wurtzite ZnO lattice [13]. The absence of the II peak suggests that the I-peak line comes from the O-Zn bonds, namely the chemical bonding of Zn-O [14].…”

Fabrication and characterization of nanostructure thin film ZnO Schottky contacts based UV photodetectors

“…The curve could be fit by Lorentzian deconvolution. This peak is attributed to O 2-ions in the wurtzite structure of hexagonal Zn 2+ ion array surrounded by Zn atoms [12,13]. Figure 5 shows XRD spectra of the ZnO films deposited on Si substrate techniques.…”

Optical properties of post-annealed ZnO:Al thin films studied by spectroscopic ellipsometry

“…The carrier concentration of the films increased, while resistivity decreased, with the increasing annealing temperature. The increase in the carrier concentration can be attributed to the formation of oxygen vacancies (V O ) near the surface of annealed thin films [18].…”