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ZnO thin films were deposited on (0001) Al2O3 substrates depending on oxygen partial pressure by pulsed laser deposition. Optical properties of ZnO were investigated by photoluminescence (PL). The relationship between PL and electron concentration has been investigated. Origin of the dominant ultraviolet (UV) emission in ZnO thin film measured at room temperature was identified as a free electron-neutral-acceptor transition (eA0) through temperature dependence of PL measurement. The UV emission intensity at room temperature is related to variation of electron concentration because a free-electron-neutral-acceptor transition (eA0) as origin of UV emission at room temperature is related to impurity concentration of ZnO.

ZnO thin films were fabricated by pulsed laser deposition. ZnO thin films showed the various photoluminescence bands centered around ultraviolet (380 nm), green (490–530 nm), yellow (570–590 nm), and orange region (610–640 nm) depending on fabrication conditions or impurity doping with Si and P. Pure ZnO thin film showed ultraviolet emission and green emission and Si-doped ZnO exhibited ultraviolet and yellow emission, the intensity of which was controlled by an annealing process. Orange and yellow emission were controlled by P and Si diffusion into ZnO. Si doping and P doping were confirmed by Rutherford back scattering (RBS) and secondary ion mass spectrometry (SIMS). The mechanism of visible emission of ZnO was investigated.

Zn 1− x Cd x O films were grown on (0 0 0 1) sapphire substrates by pulsed laser deposition. Structural and optical properties of Zn 1− x Cd x O films were strongly correlated to the processing conditions. The optical energy band gap of Zn 1− x Cd x O thin films, measured by photoluminescence and transmittance, changed from 3.248 to 3.291 eV at 275 K. Increase of Cd content also leads to the emission broadening and degraded crystallinity. The absorption edge and ultraviolet emission peak shift to lower energy from 3.291 to 3.248 eV and 3.278 to 3.106 eV, respectively, with increasing Cd content from 0.3% to 3% at 275 K. The Stokes’ shift between the absorption and emission indicates the increase of localization of exciton with Cd content. Stokes’ shift increases with Cd content caused mainly by the localized states in ZnCdO films.

Phosphorus doped ZnO multilayer (ZnO:P) thin films were deposited in various oxygen partial pressures on (001) sapphire substrates by pulsed laser deposition (PLD). The phosphorus doped ZnO multilayer was deposited with a phosphorus doped ZnO layer and two pure ZnO layers on a sapphire substrate at various oxygen partial pressures. The ZnO/ZnO:P/ZnO multilayer thin films were post-annealed at 400 ∘C for 40 min. The top ZnO layer plays an important role to encapsulate phosphorus atoms in the ZnO:P layer activated by a post-annealing process. The carrier concentration could be controlled by using a ZnO multilayer structure. The structural, electrical and optical properties of the ZnO multilayered thin films have been investigated by X-ray diffraction (XRD), Hall measurements and photoluminescence (PL).

The solid-solid interaction and thermal decomposition behavior of 2wt% Ag2O in ZnO powder have been investigated by using thermogravimetry analysis and differential thermal analysis. Ag2O, which remained stable in ZnO up to 200°C, was observed to be thermally decomposed to Ag+ ions in the temperature range of 200–250°C, suggesting that Ag+ ions were diffused into ZnO matrix. Based on thermal analysis, ZnO:Ag films have been fabricated on a (001) Al2O3 substrate using specifically synthesized Ag-doped ZnO target by pulsed laser deposition. The effect of (002) peak shift on the structural property of Ag-doped ZnO films has been systematically characterized to investigate the influence of the substitution of Ag+ for Zn+. Ag-doped p-type ZnO films have been successfully grown at a deposition temperature in the range of 200–250°C, which is in good agreement with thermally decomposed temperature for Ag2O to Ag+ in ZnO powder, with hole concentrations of 4.9×1016–6.0×1017cm−3, hole mobilities of 0.29–2.32cm2∕Vs,...

The photoluminescence spectra of As doped p-type ZnO thin films reveal neutral acceptor bound exciton of 3.3437eV and a transition between free electrons and acceptor levels of 3.2924eV. Calculated acceptor binding energy is about 0.1455eV. Thermal activation and doping mechanism of this film have been suggested by the analysis of x-ray photoelectron spectroscopy. p-type formation mechanism of As doped ZnO thin film is related to the AsZn–2VZn complex model. ZnO-based p-n junction was fabricated by the deposition of an undoped n-type ZnO layer on an As doped p-type ZnO layer.

p-type ZnO films have been fabricated on a (0001) Al2O3 substrate, using Ag2O as a silver dopant by pulsed laser deposition. The structural property of those films is systematically characterized by observing the shift of (0002) peak to investigate the substitution of Ag+ for Zn+. Narrow deposition temperature for Ag-doped p-type ZnO films has been obtained in the range of 200–250°C with the hole concentration of 4.9×1016–6.0×1017cm−3. A neutral acceptor bound exciton has been clearly observed by photoluminescence emitted at 3.317eV in Ag-doped p-type ZnO thin films.