The Study Of Character Of Silicon Quantum Dots Upon Thermal Annealing Of Silicon Carbide Films

When the feature size of material is getting smaller, the quantum size effect, quantuminterference effect, non-linear optical effect, quantum tunneling effect, Coulomb blockadeeffect and surface and interfacial effect will behave more obvious, which result in somedifferent physical and chemical properties from macroscopic materials. So that siliconquantum dots have a wide development prospect in the area of semiconductor device likeLED, solar cells and storage.Plasma-enhanced chemical vapor deposition (PECVD) is used to deposit anon-stoichiometric silicon carbide film with SiH4and CH4as reactant gas. Parameters suchas the flow ratio of reactant gas, the power of radio source, the temperature of substrate andthe time of reaction were optimized. Thermal annealing, as the most critical step in theexperiment, is used to achieve the silicon quantum dots.Firstly, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-raydiffraction (XRD) spectroscopy shows the mechanism of the formation of silicon quantumdots with the annealing temperature changing. From the perspective of the change ofchemical bonds, a large number of hydrogen atoms are existed in the film. With the rising ofannealing temperature, chemical bonds like SiHn, CHn, Si-CH3and C-SiH are broken, so thathydrogen atoms are overflew and silicon atoms with dangling bonds combine with eachother. From the perspective of the crystallization, the crystallization and growth of siliconquantum dots are promoted with the rising of annealing temperature. When the annealingtemperature increased from900℃to1050℃, the crystallinity of the silicon quantum dotsincreased from40.1%to42.3%, and the average size of them is also increased. Secondly, thephotoluminescence (PL) spectrum is used to analysis the luminescent property of siliconquantum dots. When the annealing temperature is lower than1050℃, the red shift of peaksof silicon quantum dots can be attributed to the increasing of the average size of siliconquantum dots. When the annealing temperature is higher than1050℃, the blue shift of thepeaks may due to the connection between the silicon quantum dots. Finally, the morphologyof silicon quantum dots is revealed by transmission electron microscopy (TEM) images, andthe average size of them is about3-4nm, which is consistent with the calculated results.