Nano ZnO Thin Films Research Articles

Effect of Ga Doping Concentration on Electrical and Optical Properties of Nano-ZnO:Ga Transparent Conductive Films

Transparent conductive nano ZnO thin films with different Ga doping concentrations (1, 3, 5, 7 at.%) were prepared on glass substrate by RF magnetron sputtering. The influence of Ga doping concentration on the structural, electrical and optical properties of ZnO:Ga films was investigated by XRD, SEM, Hall measurement and optical-transmission spectroscopy. It shows that the nano ZnO:Ga films are dense and flat, and have polycrystalline structure with preferential (002) and weak (101) orientation. The grain sizes, carrier concentration and Hall mobility changes non-linearly with the increase of Ga-content. The lowest resistivity of 1.44×10−3 Ωcm appears at 3 at.% Ga doping concentration. The average transmittance of the films is about 80∼90% in the visible range. The optical band gap obtained for these films is larger than for pure ZnO (∼3.37 eV).

Effect of Substrate Temperature on the Properties of Nano-ZnO: In Transparent Conductive Films

High quality transparent conductive In-doped nano-ZnO thin films with In content of 2 at% were prepared by RF magnetron sputtering. The effect of substrate temperature on the structure, electrical and optical properties of nano-ZnO thin films was investigated by XRD, Hall measurement and optical transmittance spectroscopy. It shows that all the films are polycrystalline with hexagonal wurtzite structure and c-axis is perpendicular to the substrate. The grain size of the films changed from 22.4 to 28.7 nm with different substrate temperatures. The lowest resistivity of the films obtained is 3.18×10−3 Ω⋅cm as the growth temperature is 100 °C. The transmittance of all the films is about 85% in the visible region, and the optical band gap is in the range of 3.40∼3.45 eV.

Effect of Thickness on the Properties of Ga-doped Nano-ZnO Thin Films Prepared by RF Magnetron Sputtering

Nano transparent conductive oxide (TCO) Ga-doped ZnO (GZO) thin films with thickness from 260 nm to 620 nm were prepared on glass substrates by RF magnetron sputtering from a powder target with 3 at.% Ga2O3. The substrate temperature was kept at 300 °C. The effect of thickness on the structural, electrical, and optical properties of GZO thin films was investigated. It shows that the nano-GZO films are dense and flat, and have polycrystalline structure with preferentially in the (002) orientation. With the increase of thickness, the crystallinity and the grain sizes of the films are improved, meanwhile the carrier concentration increases and the lowest resistivity of 3.685×10−3 Ω cm occurs in the 620 nm thick GZO film. The average optical transmittance of all the films is over 80% in the visible range. Decreasing the thickness, the optical transmission of the films increase, and the absorption edge shifts to shorter wavelength, which means the optical band gap is broadened.

Preparation and characterization of nano and microcrystalline ZnO thin films by PLD

Nano and microcrystalline ZnO thin films were prepared on glass substrates using pulsed laser deposition technique under a vacuum of 3 × 10 −7 Torr at different laser power density. Composition analyses show that the films deposited at low laser power density have more structural defects than the film deposited at high laser power density. It confirms that the content of Zn in free-state decreased greatly at high laser power density. Atomic force microscopy analysis shows that the surface roughness of the deposited films increases with an increase in laser power density. X-ray diffraction analyses show that all the films are oriented along (0 0 2) direction independently on the laser power density applied. The structural quality increases with an increase in laser power density. It is due to the fact that the increase of laser power density leads to the enhancement of peak intensity. The increase of laser power density reduces the film transmission in the visible range of the spectra. The optical band gap value is found to be in the range from 3.42 to 3.39 eV. It shows that the optical band gap value decreases with an increase in laser power density. FTIR analysis shows that the hydrated oxide content in the deposited films decreases with an increase in laser power density.

Structure and Photoluminescence of Nano-ZnO Films Grown on a Si(100) Substrate by Oxygen- and Argon-Plasma-Assisted Thermal Evaporation of Metallic Zn

Nano-ZnO thin films were prepared by oxygen- and argon-plasma-assistedthermal evaporation of metallic Zn at low temperature, followed bylow-temperature annealing at 300 degrees C to 500 degrees C in oxygenambient. X-ray diffraction patterns indicate that the nano-ZnO filmshave a polycrystalline hexagonal wurtzite structure. Raman scatteringspectra demonstrate the existence of interface layers between Zn andZnO. Upon annealing at 400 degrees C for 1 h, the interface modedisappears, and photoluminescence spectra show a very strong ultravioletemission peak around 381 nm. The temperature-dependent PL spectraindicate that the UV band is due to free-exciton emission.