Research On Microstructure And Properties Of Silicon Based Embedded Nano-composite Thin Films Prepared By APCVD

In this thesis, the structure, preparation method and basic properties of embedded nano-composite materials and photo luminescence of nanocrystalline silicon have been summarized. Research of photoelectric devices using several kinds of silicon-based nano-materials has also been presented.The micro structure of the films prepared with SiH4 as the source gas by atmosphere pressure chemical vapor deposition (APCVD) and its influence on the photoluminescence and optical properties have systematically studied by the means of the measurements of TEM HREM XPS SEM and Raman. The nano-crystals of Si are found embedded in the amorphous matrix in the unannealed sample. The crystallinity of the films is increased with raising deposit temperature. When deposit temperature is raised from 450℃ to 500℃, the size of nano-crystals is increased from l~4nm to 5nm. A few 8162 nano-crystals are also found, which are derived from the amorphous oxide in the matrix. Simultaneity, some special patterns appear while nano-crystals move and rearrange. When anneal temperature is below 600℃, the crystallinity can not be improved obviously for short anneal time, but the crystallization trend appear. High anneal temperature and long anneal time do good on increasing the size and density of silicon nano-crystals. At the same time, an exceptional structure has been found in the sample annealed for one hour at 800℃. It appears the single crystal lattice irradiated by high-energy electron beam within a few seconds and then becomes amorphous structure quickly.The photoluminescence of the thin films without post heating shows that the increasing of the deposit temperature decreases the PL intensity. Only the sample deposited at 450℃ has one evident luminescence band found nearby 523.2nm. If the anneal temperature is increased or the anneal time prolonged, the PL intensity could be raised in evidence. By comparable investigation, two luminescence mechanisms can explain the different variety of PL intensity of origin and annealed samples and are dominant mechanisms separately in unanneal and anneal course.The optical property of the thin films has systematically been studied. The thickness and crystallinity both influence the transmission and reflectance of films. High deposit temperature leads to transmission falling of the unannealed films. But the average transmission of sample deposited at 500℃ is higher than that at 450℃. After dealing with post heating at the same deposit temperature, the average of transmission and reflectance of the films are smaller than unannealed ones but Eopt is enlarged.