Impact of the particles impingement on the electronic conductivity of Al doped ZnO films grown by reactive magnetron sputtering (original) (raw)
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Journal of Physics: Conference Series, 2013
High quality Aluminium-doped Zinc Oxide (AZO) films have been obtained by suitably controlling the magnetron sputtering parameters and the substrate temperature. The Xray diffraction studies showed that a transition of orientation from (002) plane to (103) plane, versus substrate temperature. The surface morphology characterized by scanning electron microscopy and atomic force microscopy exhibited a dense and compact structure at higher temperature. For 200 nm thick AZO films deposited at temperature 530°C, using a ZnO target with an Al 2 O 3 content of 3 wt%, the lowest electrical resistivity is 6.810 -4 .cm and transmittance is over 85% in the visible spectral region. The conductivity improvement of AZO films was closely related to the crystallanity characterized by the (103) orientation and the densely packed structure.
Thin Solid Films, 2020
In the present study, a ZnO seed-layer assisted sputtered deposition approach is used to enhance the carrier mobility and electrical conductivity of Al doped ZnO (AZO) thin film. The seed layer assisted grown AZO thin film showed an electrical conductivity, optical transmittance, and high figure-of-merit of 1806.94 ± 10.50 S/ cm, >90% (Vis-NIR), and 1.68 × 10 −2 Ω −1 , respectively. This high optoelctronic properties make AZO thin film qualified to be used for transparent electrode applications. The carrier mobility in the seed-layer assisted grown AZO thin film is observed to be 15.21 ± 0.04 cm 2 /Vs which is twofold higher than AZO thin film grown without seed-layer. The origin of enhanced carrier mobility is investigated in the light of generated defects and their nanoscale distribution in the polycrystalline AZO thin film during the sputtering process. The low grain boundary potential is observed in seed layer assisted grown AZO thin film using nanoscale Kelvin probe force microscopy and was attributed to the low defects segregation towards grain boundaries. The argument of low carrier defects like zinc interstitial and oxygen vacancies in seed-layer assisted grown AZO thin film is experimentally verified using X-ray photoelectron spectroscopy analysis. The analysis of defect chemistry and their nanoscale distribution helps us to understand that intrinsic defects and their segregation at grain boundaries critically affect the carrier mobility in AZO thin film.
Electronic structure of conducting Al-doped ZnO films as a function of Al doping concentration
Ceramics International, 2015
Transparent conducting Al-doped ZnO films were deposited by atomic layer deposition with various of Al doping concentrations. In order to explain the change in resistivity of Al-doped ZnO films depending on Al doping concentration, we investigated the correlations between the conducting property and electronic structure in terms of atomic configuration, the evolution of the conduction band and band gap, and band alignments (conduction band offset between minimum of conduction band and Fermi level, ΔE CB). ZnO film Al-doped at $ 3 at% and deposited at 250 1C showed the lowest resistivity, which resulted in changes in the conduction band of insulating Al 2 O 3 film, and increases in the band gap and conduction band offset (ΔE CB).
Solar Energy Materials and Solar Cells, 2011
Transparent Al-doped ZnO thin films were deposited by reactive magnetron sputtering with different oxygen flow rates. The electronic resistivity, measured by the 4 point-probe method, is very sensitive to the sample position relative to the magnetron axis: the closer the magnetron from the axis the higher the resistivity. This is more pronounced for the films deposited under higher oxygen flow rate. Neither Rutherford backscattering spectroscopy nor Zn-K edge X-ray absorption near edge structure (XANES) analyses evidenced any change in chemical composition such as a measurable variation of the oxygen stoichiometry. XANES at the Al-K and O-K edges show that (i) a portion of the aluminum atoms get positioned in octahedral conformation with oxygen, consistent with the formation of an Al 2 O 3 (ZnO) m nanolaminate structure, (ii) the films exhibit relaxed O-terminated (0001) surfaces with a higher density of empty states in more resistive samples. These two findings are believed to play a significant impact on the electrical measurements by dopant deactivation and by creating an insulating barrier at the film surface, respectively.
Materials Letters, 2012
Structural and electrical properties of off-axis DC magnetron sputtered Al 2 O 3-doped ZnO (AZO) films were systematically investigated as a function of deposition distance from the center. With increasing distance, the AZO films showed an enhanced crystallinity and a denser microstructure with a smooth surface. The AZO film sputtered at the edge of the deposition stage ($ 6 cm away from the center) showed the highest mobility ($ 10.1 cm 2 /V s) and the lowest resistivity ($ 2 Â 10 À 3 O cm) due to the high plasma and thermal power density, which was suitable for transparent conducting oxide applications.
Materials Today: Proceedings, 2017
Aluminum-doped zinc-oxide (AZO) thin films were deposited on silicon wafers and glass substrates by a pulsed DC magnetron sputtering at room temperature. The influence of different sputtering powers during the film deposition towards the obtained thin films was investigated. The crystal structures, physical morphologies, optical transmission, and electrical properties of the AZO films were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), spectrophotometer, and hall-effect measurements, respectively. The results demonstrated that all the AZO thin films exhibited the hexagonal structure, where the growth orientation between (002) and (103) were changed with the increase of the sputtering power. In addition, the average transmission of the AZO thin films was high to 87% in the visible region, indicating that the optical transmission was significantly influenced by the sputtering power. Furthermore, the resistivity, the charge mobility, and the carrier concentration of the AZO thin films were improved with the increased sputtering power. Finally, the improved conductivity related to the film crystallinity and thickness was determined and discussed.
Journal of Physics D: Applied Physics, 2010
We report on the possible origin of electrical heterogeneities in 4 at% Al-doped ZnO (AZO) reactively sputtered films. It is found through the Zn L 3 and Al K edge x-ray absorption near-edge structure that a fraction of the Al dopant is deactivated by its positioning in octahedral conformation with oxygen. This fraction as well as the conductivity, optical bandgap and c-axis parameter of ZnO wurtzite are all found to depend on the sample position during deposition. The present results suggest the formation of a metastable Al 2 O 3 (ZnO) m homologous phase that degrades the electrical conductivity.
Applied Mechanics and Materials, 2013
Transparent conducting Al-doped ZnO (AZO) thin films were deposited on soda-lime glass substrates by DC magnetron sputtering with a sintered ceramic target, AZOY® that contains a small amount of Y2O3 in addition to Al2O3 and ZnO. The effect of substrate temperatures (Ts) on the structural, electrical and optical properties of the prepared AZO films was evaluated extensively. By elevating Ts, the electrical conductivity of the films could be effectively improved from 1.68 ×10-3 cm (no substrates heating) to a minimum resistivity of 4.6210-4 cm at Ts = 400oC with an average visible transmittance (400~800nm) of ~80%. It revealed that substrate heating is closely related to the crystallinity and the surface roughness of the deposited films. It is noteworthy that the transmittance in the NIR region was also improved considerably as compared to those using alloy targets by reactive magnetron sputtering and even slightly higher than those using Al-doped ZnO (1 wt.%) ceramic targets by...
Journal of Nanoscience and Nanotechnology, 2009
Transparent conductive thin-films of aluminum-doped zinc oxide (AZO) were deposited on STNglass substrates by an asymmetric bipolar pulsed DC (ABPDC) reactive magnetron sputtering system. Two different alloys, Zn-1.6 wt%Al and Zn-3.0 wt%Al, were used as the sputtering targets. The films consist of columnar grains with a preferred orientation of c-axis. Strong crystal distortion and high density stacking faults were observed in high resolution TEM micrographs. The full-width at half-maximum (FWHM) of the (002) rocking curve has a close relationship with the resistivity of the films; the smaller the FWHM, the lower the resistivity. The lowest resistivity of 7 0 × 10 −4-cm was obtained from the film deposited with Zn-1.6 wt%Al target at 200 C.
Electron transport in Al-doped ZnO nanolayers obtained by atomic layer deposition
Journal of Physics: Conference Series
Al-doped ZnO thin films with different Al content were prepared by atomic layer deposition (ALD). To carry out thermal ALD, diethyl zinc (DEZ) and tri-methyl aluminium (TMA) were used as Zn and Al precursors, respectively, and water vapor as oxidant. Various numbers n of DEZ and m TMA cycles was used to obtain different [ZnO] n [Al 2 O 3 ] m films, where n = 100-95, m = 1-5. The X-ray diffraction analysis showed a predominantly (100) oriented polycrystalline phase for the ZnO:Al films with a low Al content (m = 1-3) and an amorphous structure for pure Al 2 O 3. In ZnO:Al with a higher Al content (m = 4-6) the (100) reflection disappeared and the (002) peak increased. The resistivity of the films decreased with the increase in the Al content, reaching a minimum of 3.3×10-3 Ω cm at about 1.1 % Al 2 O 3 for the [ZnO] 99 [Al 2 O 3 ] 2 sample; for higher dopant concentrations, the resistivity increased because of the increased crystal inhomogeneity due to axis reorientation.