Research On The Losing Of Nitrogen In SiO_xN_y And SiC_xN_y Films

With the development of nanotechnology, nanocrystals have become the potential photoelectrical materials. SiOxNy and SiCxNy systems have a large variable range of composition and adjustable phase structures, especially, during the annealing process, the nitrogen element is easy to escape, which leads to Si or SiC nanocrystals left in the oxide matrix. It is destined to be a new method of fabricating nanocrystals.In this research, a series of SiCxNy and SiOxNy thin films with different compositions were deposited by reactive r.f. magnetron sputtering by changing the target and ratio of the flow rate of Ar and N2. Then the films were annealed at different temperatures. XPS, FTIR, TEM and PL were adopted to investigate the structre and bond types of the materials.The ratio of the flow rate of Ar and N2 is the most important parameter which affects the compositions of the films. It was found that the atomic percentage of oxygen is the lowest and nitrogen is the highest only when the ratio is 8/2. In this case, the PL intensity of the films is the highest. The compostion change arises from the different sputtering capabilities of Ar+ and N-.Target type is also an important factor affecting the composition of films. Compared with silicon target, the atomic percentage of oxygen in the films prepared with Si3N4 target was much higher, which is attributed to the different sputtering rates of the two kinds of targets. The sputtering rate of Si3N4 is lower, so more oxygen atoms were doped into the films in the longer process of deposition.As compared with annealing time, the temperature has more significant effect on the losing of nitrogen element. Visible photoluminescence (PL) originated from the Si dangling bonds was detected after annealing at 1000℃, while the PL intensity decreases as annealed at 1100℃, which may be attributed to the bonding of Si dangling bonds with O element and the reduction of luminescence centers.After annealed at 1000℃, all of the nitrogen in SiCxNy films disappeared and SiC nanocrystals with high density were observed. The as-annealed film emits UV and visible lights, which are attributed to the defects and quantum confinement effect in SiC, respectively.