Growth of Semiconductor Thin Films by Pulsed Laser Deposition

Abstract

Pulsed ultraviolet light from a XeF excimer laser was used to grow thin films of zinc oxide and tin dioxide on (111) p-type silicon wafers within a versatile high vacuum laser deposition system. This pulsed laser deposition system was self-designed and self-built. Parameters such as pressure, target temperature, and distance from the target to the substrate can be adjusted in the system. Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy and ellipsometry were used to analyze the structures and properties of ZnO and SnO2 thin films. The critical temperature required to fabricate a crystalline ZnO thin film by pulsed laser deposition was found and has been confirmed. For the SnO2 thin film, the critical temperature required to generate a crystalline structure could not be found because of the temperature limit of the substrate heater used in the experiment. In SnO2 thin films, thermal annealing has been used to convert into crystalline structure with (110), (101) and (211) orientations. After fabricating the amorphous SnO2 thin films, they were put into an oven with specific temperatures to anneal them. The minimum annealing temperature range was found for converting the amorphous SnO2 thin films into SnO2 thin films with a crystalline structure. Thermal annealing has also been applied to some amorphous ZnO thin films which were fabricated under the critical temperature required to produce crystalline ZnO thin films. The minimum annealing temperature range for amorphous ZnO thin films was found and only one orientation (002) shown after annealing. Laser annealing technology has also been applied for converting both amorphous ZnO and SnO2 thin films, and results show that this method was not well suited for this attempt. ZnO thin films and SnO2 thin films with a crystalline structure have inportant widely used in industry, for example, application in devices such as solar cells and UV or blue-light-emitting devices. The aim of this research is to help improving the manufacturing process of ZnO and SnO2 thin films.