Structural, optical and electrical properties of ZnO and ZnO-Al 2 O 3 films prepared by dc magnetron sputtering

Abstract

ZnO and ZnO-Al 2 O 3 thin films were prepared by dc magnetron sputtering and their structural, optical and electrical properties were studied comparatively. It is discovered that the ZnO-Al 2 O 3 thin films remain transparent in a shorter wavelength range than the ZnO films, resulting from the increase of their band gap. Their resistivity decreases by seven orders of magnitude, which is caused by doping of Al to ZnO grains in the film. Preferential orientation of ZnO grains in the ZnO-Al 2 O 3 thin films deteriorates because of the existence of Al 2 O 3 impurity phase in the film. 68.55; 78.65; 73.60 ZnO thin films have many practical applications owing to their interesting properties. They are used in various pressure transducers, acoustic wave and acoustic-optical devices with their piezoelectric properties [1,2]. They are useful as transparent electrodes in panel displays and solar cells while doped with Al, In etc., and as catalytic combustion sensors while doped with Pt and Pd [3]. PACS:Another important application of ZnO films is the use as a buffer layer for the growth of GaN films. Recently, improvement of the GaN blue light-emitting diode [4] has made it possible to display full color by semiconductor [5]. One of the problems that has plagued further development of GaN film is lack of high-quality, closely lattice-matched substrate materials [6]. People often deposited GaN films on sapphire substrate although it has large lattice dismatch and thermal expansion. ZnO is closely lattice matched to GaN and has the same crystal structure. Therefore, the ZnO film offers the potential to be a substrate on which high-quality GaN films may be grown.As the development in flat panel displays frequently requires the improvement of electrical, optical, and chemical properties of the transparent electrodes, scientists are searching for new materials consisting of ternary or multicomponent oxides suitable for special applications. In 2 O 3 -SnO and ZnO:Al films have received much attention [7,8]. ZnO:Al films have the advantages that they can be produced at low substrate temperature and etched easily. But many research works focus on low Al content in ZnO films.This paper reports the preparation of ZnO-Al 2 O 3 and pure ZnO films by dc magnetron sputtering. The structural, optical, and electrical properties were compared between these two kinds of films. The possibility of ZnO-Al 2 O 3 films as a buffer layer and transparent electrodes of blue emitter diode is discussed. ExperimentSputtering targets were made from pressing pure Zn powder and Zn/Al(1:1) premixed powder, respectively, under the pressure of 6 × 10 8 Pa. The targets were then calcined in a vacuum furnace at 420 • C for 4 h, then polished and cleaned for sputtering. Intrinsic silicon and quartz glass plates were cleaned by alcohol in a supersonic wave apparatus and used as substrate.The ZnO and ZnO-Al 2 O 3 thin films were prepared by conventional planar magnetron sputtering. The deposition was carried out under dc power of 25 W, in an Ar and O 2 ambien...

Structural and X-Ray Photoelectron Spectroscopy Study of Al-Doped Zinc-Oxide Thin Films

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Highly transparent, UV‐B protective Al–Zn–O films with potential application in greenhouse screen systems

“…Thickness‐induced blue shifts in the optical band gaps of Al–Zn–O films have also been reported, partly attributed to an increase in the atomic percent of the aluminum and oxygen contents . Furthermore, it has been observed that the optical band gap of ZnO films shifts toward lower wavelengths as the films are alloyed with Al 2 O 3 …”

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Study the Effect of ZnO/Cu/ZnO Multilayer Structure by RF Magnetron Sputtering For Flexible Display Applications

“…This balanced electrical and optical properties of TCO makes it useful for a wide range of applications in flat-panel displays, solar cells, gas sensors, thin film transistor (TFT), liquid crystal displays (LCD), photovoltaic devices, organic light emitting diodes (OLEDs) and smart windows. [3][4][5][6][7][8] TCO films can be deposited by different deposition techniques such as spray pyrolysis, [9] solgel process, [10] pulsed laser deposition, [11] thermal evaporation, [12] chemical vapor deposition, [13] electron beam deposition [14] and radio frequency (RF) magnetron sputtering [15][16][17] on various substrate. Among different deposition techniques RF magnetron sputtering technique is more beneficial due to its uniformity and high deposition rates.…”