Study On Photoluminescence Enhancement And Stimulated Radiation Of Silicon Nanocrystals

Silicon nanocrystal has become a promising material for optical-electronic in-tegration. Comparing with bulk silicon, silicon nanocrystal holds properties of photoluminescence, electroluminescence and stimulated emission. It also ad-vanced in physical and chemical stability with other nano-structured silicon mate-rial such as porous silicon. Moreover, silicon nanocrystal is compatible with recent practice in silicon-based semiconductor industry.The following issues are discussed in this thesis:1. The obtaining, enhancement and modification of photoluminescence (PL] from silicon nanocrystal are studied. The samples were made by reactive evapora-tion of silicon oxide and silicon dioxide, followed by annealing in nitrogen for one hour at1100degree Celsius. Raman, XRD, HRTEM and PL tests were performed to characterize the formation of silicon nanocrystal. Treatments such as passivation, doping and ion-sputtering were used to modify the PL of the samples. Hydrogen passivation and Ce3+dopoing were found most effective in increasing PL intensity. The Matrix effect and its influence on the PL of silicon nanocrystal were discussed in detail. Samples with different materials as the buffer layer were made. By chang-ing the environment matrix of silicon nanocrystal from silicon dioxide to silicon nitride, it was found that the PL intensity will change due to the band gap constrain from the matrix in which the silicon nanocrystal embedded.2. Surface states treatments will influence the PL of silicon nanocrystal. We utilized hydrogen, oxygen and ammonia to anneal as-prepared samples with sili-con nanocrystals and analysis the PL change due to these treatments. The analysis includes the intensity, position and shape of the peak. Through this the role that surface states played in the photoluminescence of silicon nanocrystals is discussed.3. The stimulated emission from silicon nanocrystal is studied by performing VSL and SES test to silicon nanocrystals emdedded thin films. The fitting result shows that the optical gain of silicon nanocrystals can reach114cm-1. These tests were also performed to other samples with different surface states treatments us-ing different pumping power densities. Detailed study of these results showed that samples with higher PL intensity obtain larger optical gain, which indicated the possibility towards a silicon-based laser through ultilizing high PL intensity silicon nanocrystals.4. A brief discussion on the preparation of waveguide structure using the sili-con nanocrystals embedded thin film is shown at the last chapter. With the help of ellipsometry, optical constants of silicon nanocrystals were found out. Waveguide structure design was studied thanks to computer simulation tools. Building silicon nanocrystal embedded thin film as gain mediums for a silicon laser in the future research is also discussed.