Luminescence study of silicon nanostructures prepared by ion beam mixing
Introduction
There is currently an increasing interest in Si nanoclusters as a material that offers new application in silicon-based optoelectronics and is compatible with silicon IC technologies. Especially, Si nanoclusters obtained by high temperature annealing of deposited SiOx layers are a subject of attention due to intense visible and IR luminescence and simple fabrication process. Among the various methods applied to synthesize SiOx, silicon ions implantation offers great potentialities. It is a versatile technique where many parameters can be easily modified and controlled. Nevertheless the following limitations exist: the total amount of implanted atoms is limited by sputtering phenomenon; depth homogeneity of implantation profiles is hardly achieved; all reported Si+ implantation results concerned only thermal oxide and Si substrate. Ion beam mixing of deposited films stack provides a new technique to form SiOx and Si nanoclusters by keeping the most important advantages of direct Si+ implantation without the drawbacks mentioned above [1], [2].
Photoluminescence (PL) and electroluminescence (EL) from Si nanoclusters obtained by various technique has been extensively studied. It is now commonly accepted that quantum confinement in Si nanoclusters and radiative recombination at the interface states of clusters are the processes responsible for observed emission. In this paper, we present our work on the PL and EL results from annealed SiOx layers obtained by ion beam mixing of a-Si/SiO2 multilayer films (MLF) by different ions. The results show quantum confinement origin of luminescence from created Si nanoclusters.
Section snippets
Results and discussion
a-Si/SiO2 multilayer structures were deposited by a PECVD system on (100) p-Si wafers as described elsewhere [3]. Different samples with 4 periods were made to find the effect of a-Si/SiO2 layer thickness ratio on PL and EL. For mixing of MLF Ar (65 keV) or Kr (130–200 keV) ions were used with doses in the range of 5×1015–5×1016 ions/cm2. Samples were furnace annealed at temperatures 1000 and 1100 °C for 1 h in N2 atmosphere. A semitransparent Au electrode of 20 nm thickness and 2.5 mm diameter
Conclusion
We have proposed to use ion beam mixing for silicon nanostructure fabrication from multilayered a-Si/SiO2 film. The existence of nanoclusters was proved by TEM image and luminescence study of the nanostructures prepared at different conditions. It was showed that ion beam mixing is most effective when maximum of nuclear energy loss is situated in the middle of multilayered film. Dose dependence of luminescence efficiency has maximum due to negative influence of accumulated in MLF mixing atoms.
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