| The main aim of this project is to suvey the preparation method and properties of the ZnO thin films, trying to find a new way to fabricate ZnO. In our research, we combine the advantages of both PLD ( pulsed laser deposition ) and ECR (electron cyclotron resonance) discharge method, forming a new thin film growth technique: Electron cyclotron resonance plasma assisted pulsed laser deposition, ECR-PLD. Based on this new method, ZnO thin films were successfully prepared, following by research on the properties of those films. Besides, N element was successfully doped into ZnO film. The efforts on N-dopped ZnO were also discussed in this thesis.Pulsed laser deposition, also known as PLD, came to application sooner after the inventation of laser. However, limited by the technologies at that time, the advantages of PLD was not obvious. Therefore it was not widely researched and applied until superconductive materials were synthesized by PLD in 1970s, but now PLD has been used in various materials fabrication. Electron cyclotron resonance (ECR) microwave discharge method can work at low pressure, producing plasma with high density, high ionization and high purity. Combining these two methods together, a new kind of method, which can be used in thin film preparation, was carried out. Pulsed lasers, when focused, heat the surface of target to an extremely high temperature in a small region, which help to break the non-equilibrium theremodynamic limitations; while with ECR discharging, another plasma was produced, full of active chemical components. Meanwhile plasma produced by ECR discharge method can also improve the properties of thin film by providing additive energy. In this thesis, researches were conducted on the properties of ZnO thin films prepared by PLD and ECR-PLD respectively, following with discussions on the influence of preparation conditions.Zinc Oxide is a direct-band semiconductor material with wide bandgap. Optical devices, which can emit blue light or even UV light, can be made in the use of this property. However, in normal method, ZnO shows Zn-rich effect and result in n-type, limiting the application in devices. According to former research, impurities can be found in ZnO, which will also degrade its electric properties. Thus how to grow c-axis ZnO, helping electrons and holes move easiy in the surface's plane, became a new topic in the research field. Moreover, Si is a main materials used in semiconductor intergration and it is easily to be contaminanted when heated or annealled. Therefore, a research on fabrication at room temperature is also essential for further study.Through experiments, it is found that ZnO thin film can be prepared by PLD, but the film properties are far from satisfactory and no c-axis growth was found before annealing. However, when ECR enhance pulsed laser deposition was applied, the properties of thin film was greatly improved. This method made it possible to prepare ZnO with good orietaion of (002) on Si (100) substrate.Doping method is another main research on this material. ZnO shows different properties, including magnatic and electric, after being doped with different elements. It is also reported that p-type ZnO was successfully fabricated through doping group I or group V elements. It is easily to realize N-doped ZnO through ECR-PLD technology and it was also proved that N incorporated into ZnO thin film, improving the performance of ZnO.It is also proved in our research that ECR enhanced pulsed laser deposition can that prepare composite thin films at room temperation, through reaction between two different plasmas. This technology can help with the growth of thin film and improve the electric, crystal and optical properties. Research and disucussion will conducted on ZnO thin films prepared by PLD and ECR-PLD respectively, and N-doped ZnO through ECR-PLD will also be discussed in this thesis. |
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