Electrical Properties Of Al-doped ZnO Films Research Articles

Al concentration-dependent electrical modulation of Al-doped ZnO thin film using atomic layer deposition

A series of 150-nm-thick Al-doped ZnO (AZO) thin films with various Al doping concentrations were deposited by atomic layer deposition technique to determine their applicability in transparent electronic devices. For incorporation into transparent electrodes, the electrical properties of AZO films must be modulated to minimize the parasitic effect. The results show that AZO thin films with various Al dopant concentrations had different work-functions and electrical contact properties, while the other physical characteristics were not significantly changed. Hence, AZO thin films can be used as transparent conducting oxide materials and are potential alternatives for the currently used indium-tin-oxide (ITO) thin films.

Impact of atomic layer deposition temperature on electrical and optical properties of ZnO:Al films

This work highlights the impact of growth temperature on the electrical and optical properties of Al-doped ZnO (AZO) films deposited by the atomic layer deposition (ALD) technique. The ALD process and super-cycle sequence have been optimized, identifying their influence on film resistivity. By using this optimum ALD procedure, the optical and electrical properties of AZO films have been widely analyzed considering the deposition temperature. Results show promising values with film resistivity in the range of 1 mΩcm and average optical absorption below 2% for 50 nm thick AZO layers. Hall effect, X-ray diffraction and ellipsometry measurements point out that these excellent values are related to their high carrier concentration and mobility, crystalline phase and optical band gap, resulting in ALD AZO films with excellent properties to be applied in photovoltaic devices as transparent conductive oxide electrode.

Effects of substrate temperature on thermal stability of Al-doped ZnO thin films capped by AlOx

Effects of substrate temperature on the thermal stability of Al-doped ZnO (AZO) films have been studied. Degradation of electrical properties of AZO films by annealing under flowing N2 gas depends on their crystallinity controlled by the substrate temperature. A thin AlOx capping layer was employed to passivate the thermal degradation of the AZO layer. A strong correlation between Zn desorption and reduction in carrier concentration was observed. Thermal desorption of Zn was prevented by the AlOx layer, retaining carrier concentration. With the AlOx capping layer, the reduction in Hall mobility was prevented in samples with good c-axis orientation, while the reduction in Hall mobility was still observed in poor c-axis oriented films. However, the reduction was smaller than that in bare AZO films. The dependence of Hall mobility evolution on the substrate temperature, and therefore, on crystallinity, strongly suggests the impact of grain boundary scattering on thermal degradation. An increase in optical mobility, which was evaluated from optical spectra using the Drude model, with annealing temperatures, supports the conclusion that an increase in grain boundary scattering by annealing caused the degradation of Hall mobility. The increase in grain boundary scattering induced by Zn desorption was prevented by the capping layer, while contributions of domain alignment and other segregation of defects to the grain boundary scattering, which depend on the substrate temperature retained, leading to different evolutions of Hall mobility.

Influence of annealing duration on structural, optical and electrical properties of AZO thin films grown on corning glass by dc magnetron sputtering

Al doped ZnO (AZO) thin films were deposited using dc magnetron sputtering on corning glass substrate has successfully done. After deposition, the samples were annealed in vacuum ambient at temperature of 300 °C with variation in annealing duration of 0, 30, and 50 minutes, respectively. The structural, optical and electrical properties of these films have been investigated as a function of annealing duration. Thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-Vis spectrometer and I-V measurements. AZO thin films without annealing treatment was showed amorphous structure. However, after annealed at 30 and 50 minutes, the films obtained were polycrystalline with a hexagonal wurtzite structure and preferred orientation in the (002) plane. Average optical transmittance of the AZO thin films was over 85%. In Addition, the electrical resistivity is reduced from 1.85 × 106 Ωcm to 1.93 × 102 Ωcm when applying annealing treatment. It’s can be concluded, the annealing treatment in vacuum ambient was improved the crystallinity and simultaneously improved optical and electrical properties of AZO films.

Tailoring of optical and electrical properties of transparent and conductive Al-doped ZnO films by adjustment of Al concentration

Highly optically transparent and electrically conductive Al-doped ZnO (AZO) thin films with varied Al concentrations were synthesized by means of reactive deposition of ZnO host films and in-situ doping of Al by pulsed laser co-ablation of a Zn target and an Al target with the assistance of an oxygen plasma. The optical and electrical properties of AZO films were tailored by the adjustment of Al concentration which was realized by varying the laser fluence on the Al target. The morphology, composition and structure as well as the optical and electrical properties were characterized and the effects of Al doping and post-deposition annealing were investigated. Similar with undoped ZnO, the synthesized AZO films have a hexagonal wurtzite structure with the crystallinity deteriorated, present high visible transparency with the absorption edge blue shifted and show good electrical properties with the electrical conductivity increased. The structural, optical and electrical properties are strongly dependent on Al concentration and are significantly improved after annealing in H2/N2 mixed gas. Annealed AZO films containing 3.0at% Al have optical properties including an absorption edge near 325nm and an optical band gap of 3.67eV and electrical properties covering an electrical resistivity of 5.27 × 10−4Ωcm and a carrier concentration of 1.11 × 1021cm−3 with a Hall mobility of 10.7cm2/V s.

Characterization of Al-Doped ZnO Transparent Conducting Thin Film Prepared by Off-Axis Magnetron Sputtering

The off-axis sputtering technique was used to deposit Al-doped ZnO (AZO) films on glass substrates at room temperature. For the illustration of the sample position in the sputtering chamber, the value ofR/ris introduced. Here,ris the radius of AZO target and R is the distance between the sample and the center of substrate holder. A systematic study for the effect of deposition parameters on structural, optical, and electrical properties of AZO films has been investigated in detail. As the sample position ofR/ris fixed at 1.8, it is found that the as-deposited AZO film has relatively low resistivity of 2.67 × 10−3 Ω-cm and high transmittance above 80% in the visible region. Additionally, after rapid thermal annealing (RTA) at 600°C with N2atmosphere, the resistivity of this AZO film can be further reduced to 1.19 × 10−3 Ω-cm. This indicates the AZO films prepared by off-axis magnetron sputtering and treated via the appropriate RTA process have great potential in optoelectronic applications.

Properties of Al doped zinc oxide films prepared by electron beam-PVD

Al doped ZnO (AZO) films were prepared on quartz substrates by the co-evaporation of ZnO and Al2O3 by EB-PVD. Structural, optical and electrical properties of AZO films were investigated, focusing on the effect of the electron beam power applied to the Al2O3 ingot. X-ray diffraction measurement showed that the AZO films were highly c-axis oriented. Transmittance of all the AZO films was over 85% in the visible range. The highest reflectance in the near IR range was obtained at the EB power on Al2O3 of 7.5 kW, 73% at 2500 nm. The lowest resistivity of 2.34 × 10−4 Ωcm was obtained for the film deposited with the EB power on Al2O3 of 7.5 kW.

Highly conductive and transparent Al-doped ZnO films on glass substrate via incorporating hydrogen at low substrate temperatures

Al-doped ZnO (AZO) transparent conducting films were prepared on glass substrates by RF magnetron sputtering at substrate temperatures of 100°C and 250°C with various hydrogen contents in sputtering ambient. The effects of substrate temperature on the effectiveness of hydrogen incorporation in Al-doped ZnO films were compared and investigated. The microstructural, electrical and optical properties of AZO films were systematically analyzed by surface profiler, X-ray diffractometry, scanning electron microscope, four-point probe measurement and UV/vis spectrophotometer. The results indicate that hydrogen is incorporated at low substrate temperature is more effective in improving crystallinity and electrical properties of AZO films than at high substrate temperature. The lowest resistivity of 6.0×10−4Ω⋅cm and the average transmittance of more than 85% in the visible range were obtained with hydrogen incorporation at substrate temperature 100°C.

Effect of Substrate Temperature on the Properties of Al-Doped ZnO Films by RF Magnetron Sputtering

The Al-doped ZnO (AZO) films were deposited on the glass substrates by RF magnetron sputtering at different substrate temperatures. The effect of substrate temperature on the structural, optical, and electrical properties of AZO films was investigated. The results indicate each of the films has a preferential c-axis orientation. The grain size increases with substrate temperature increasing. All the films exhibit a high transmittance in visible region and have sharp ultraviolet absorption characteristics. The resistivity decreases with substrate temperature increasing up to 250oC, then increases for higher temperature.

Physical properties of Al-doped ZnO films deposited on nonwoven substrates by radio frequence magnetron sputtering

In this study, the polyethylene terephthalate (PET) spunbonded nonwoven materials were used as substrates for creating electro-optical functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit Al-doped ZnO (AZO) films onto the nonwovens. The influences of the deposition time on the structural, optical, and electrical properties of AZO films were investigated. Atomic force microscopy (AFM) was employed to examine the topography of the fibers. The AFM observation revealed a significant difference in the morphology of the fibers before and after the AZO sputter coating. The examination by UV–visible spectrophotometer analysis showed that the nonwovens deposited with transparent nanostructure AZO films had better UV absorption, and an average transmittance was approximately 50% in the visible light wavelength region. The surface conductivity of the materials was analyzed using a four-probe meter, and it was found that electrical resistance was significantly decreased as the sputtering time increased.

The low temperature synthesis of Al doped ZnO films on glass and polymer using pulsed co-magnetron sputtering: H2 effect

It has been reported that a small amount of hydrogen in argon plasma induces an increase in the crystallite size of the as-deposited films. In addition, control of the hydrogen partial pressure is expected to improve the carrier mobility by increasing the crystallinity of the film (larger crystal size and lower grain boundary effects). Al doped ZnO (AZO) films were deposited by co-CFUBM (closed field unbalanced magnetron) sputtering. The ultimate aim was to deposit transparent films on a polymer substrate with a low electrical resistivity. Therefore, the structural, optical and electrical properties of AZO films were investigated as a function of the hydrogen partial pressure. A minimum resistivity and maximum transparency of 8 × 10 − 4 Ω cm and 88.1% were obtained, respectively. A critical P H2 was expected to improve the carrier mobility by increasing the crystallinity of the film. However, above this value, conductivity reduced due to the formations of oxides such as ZnO and Al 2O 3 in the AZO films.