The Research On Fabrication, Property And Mechanism Of Si-based Luminescent Materials

Silicon nanocrystals can emit visible light and exhibit novel optoelectronic properties and special structure. It shows high potential on light-emitting devices, photodetector, optoelectronic devices and sensor. The porous silicon is a represent of silicon-based nanometer material, in this dissertation, the preparation process, the mechanism of formation of porous silicon and its luminescence were systematically investigated. The porous silicon was fabricated by electrochemical and chemical methods and the photoluminescence properties were measured. Intensive red, orange, yellow, green light can be seen when porous silicon was irradiated under ultraviolet light or work as positive biases. It was discovered that with the increase of the current density, anodizing time and the reduction of HF concentration, the peaks of PL shows the blue shift. When PS are exposed to the air, the intensity of PL will decrease. A novel and easy method was adopted to improve the intensity and stability of the photoluminescence.The mechanics of photoluminescence, electroluminescence and formation process are still in argument. It was discovered that the stable red and orange light-emitting was caused by quantum confinement and the surface state played an assistant role; the unstable yellow and green light-emitting was mainly caused by surface state and the quantum confinement played an assistant role. The electroluminescence of porous silicon in HCl acid at positive stemmed from the oxidation of Si-H bond on the surface of PS. We provided new proof for this theory. In addition, the relation between the formation process and the mechanism of photoluminescence was discussed and the mechanism of formation process and PL were analyzed.