Studies On Preparation And Property Of ZnMnO Films

In recent years, much attention has been given to wide band gap semiconductors for the wide use in blue and ultraviolet light emitters and detectors. ZnO is wide direct band gap semiconductor with band gap energy of 3.37 eV and 60meV exciting energy at room temperature, and it is widely used. Doping can changes the property of ZnO, so ZnXO attracts lots of scientists (X means doping element). If X is 3d transition-metal ions, ZnXO may shows magnetism and Diluted Magnetic Semiconductors (DMS) can be achieved. ZnMnO is one of them. The incorporation of Mn into ZnO not only gives rise to the introduction of magnetic moments but also increases the band gap, which allows one to increase the functionality of ZnMnO-based heterostructures.There have been some reports on the property of ZnMnO thin films. ZnMnO films grown by different methods have different properties. In this dissertation, the ZnMnO thin films have been prepared by radio frequency magnetron sputtering at low temperature (80℃) on SiO₂ glasses for the first time. The structural and optical properties of ZnMnO thin films have been systemically investigated. The influence of conditions, such as deposition power, deposition time and annealing temperature, on the characteristic of ZnMnO thin films have also been studied.In the first chapter, the characteristic and application of ZnO have been introduced first. The progress of the studies on ZnMnO has also been mentioned.In the second chapter the equipment and measure method have been introduced. The Zno.95Mno.05O films were deposited in a JPGF-450 model radio frequency magnetron sputtering system with a base pressure of 6×10^-3 Pa. A power supply operated at a crystal-controlled frequency of 13.56 MHz. The sintered ceramic targets with a mixture of ZnO (99.99%) and MnO₂ (99.99%) were employed as source material. During film deposition, the argon maintained at 1 Pa. The sputtering power was 60～140 W. In order to investigate the effect of annealing temperature on the properties of ZnMnO thin films, part samples of ZnMnO films were respectively annealed at 500℃and 600℃in the air. In the third chapter the structural properties of ZnMnO films were discussed. The structure of ZnMnO films were measured by XRD and Raman spectrum. The observation of only (0002) peak revealed the films were sing-phase hexagonal wurtzite structure and had a preferred orientation with the c axis perpendicular to the substrates. The vibration mode of E₂ appears in Raman spectra of ZnMnO, indicating that the films are of wurtzite structure. Characteristic peak of Mn was also observed.The optical properties of ZnMnO films were discussed in the fourth chapter. ZnMnO thin films are high transparent in the visible region from 400nm to 800 nm and have a sharp absorption edge in the UV region. By calculating the band gap energy of Zn_0.95Mn_0.05O is 3.37eV. UV (398nm) and green (490nm) peaks were observed in photoluminescence (PL) spectra. After annealing in the air, the intensity of the UV peak increased.The influence of deposition condition, such as power and time, on the characteristic of ZnMnO thin films have been studied in the fifth chapter.In the sixth chapter, we discuss the influence of annealing temperature on ZnMnO films. With increasing annealing temperature, the intensity of the (0002) peaks for the XRD, grain sizes and intensities of the UV photoluminescence peaks increase while the FWHM of (0002) peaks decrease, which demonstrate that the high quality of the ZnMnO films deposited by RF magnetron sputtering can be obtained by controlling annealing temperature.In the last chapter, we summarize our work.