Preparation Of Zno Thin Films And Their Uv Detection Features

Zinc oxide (ZnO) is a versatile semiconductor material with a wide band-gap of 3.37eV at room temperature (RT). It is very chemically and thermodynamically stable and is regarded as one of the most promising materials for fabricating efficient blue light emitting devices and ultraviolet (UV) photodetectors. In this paper, ZnO thin films were fabricated on glass substrates by two different kinds of techniques, one is the pulsed laser deposition (PLD), and the other is the thermal oxidation of metallic Zinc (Zn) films. We also studied UV detection characterization of ZnO thin films.1. Highly c-axis oriented ZnO films were grown on glass substrates by PLD. Ultraviolet photodetectors were fabricated based on metal-semiconductor-metal planar structures. Properties of photoconductive ultraviolet detectors were presented. Photocurrent transients show that the detector has a large photocurrent and the response curve of the detector is fitted well with exponential curve. The large photocurrent should result from the accumulation of conduction electrons. The relaxation time constant obtained from the curve fitting represents the time accumulation during the process.2. Dark conductivity transients were measured with an electric field applied, and a change of up to more than three orders of magnitude was observed. Dark conductivity transients indicate that the increase /decrease of the conductivity may be attribute to the adsorption/desorption of oxygen on the surface and the grain boundaries. For an aged film as ours, the conductivity decreases to the minimum value because of the oxygen chemisorption, and when an electric field is applied, the conductivity would increase due to oxygen desorption.3. Zn films were deposited on glass substrates by electron beam evaporation, and then were placed on the oven in an open-air environment. Polycrystalline ZnO films covered with ZnO nanobelts were grown. Ultraviolet photodetectors were fabricated on polycrystalline ZnO films covered with ZnOnanowires. The spectral response and the photocurrent transients were studied extensively. The UV photoconductivity increases by two orders. Till today, we don't find any reports like ours.