Fundamental study of nanofabrication by electron irradiation

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We have studied electron irradiation effects in semiconductor crystals by means of electron microscopy and associated experimental techniques. In addition to structural studies on electron-irradiation-induced defects in silicon, we have examined silicon surface nanoholes, which are introduced on a clean silicon surface by electron irradiation. We have experimentally determined the dependence of diameters, spatial distribution and excavating rate of silicon surface nanoholes on electron irradiation condition. This detailed date can be used for application of silicon surface nonoholes. Furthermore, we have found that gold nanoparticles of certain size can be formed on electron-irradiated silicon surface. The experimental procedure is as follows ; 1) preparation of a clean silicon surface, 2) irradiation of electron beam of the surface, 3) deposition of gold homogeneously on the surface, and 4) annealing the surface at elevated temperatures. Al the processes are carried out in ultra vacuu … More m environment. As a result, gold nanoparticles are formed selectively on either the center or the periphery of the irradiated areas at the certain experimental condition. We have analyzed this peculiar phenomenon based on a simple model. We assume that electron irradiation induces atomistic roughness on surface according to the intensity profile of electron beam. This roughness, introduced heterogeneously on the surface, affects the surface diffusion of adatoms, i.e. deposited gold atoms. Extending a basic theory of surface diffusion and clustering of adatoms to that on the heterogeneously roughened surface, we have explained qualitatively our experimental result. Furthermore, having known that the size of the selectively grown gold nanoparticles on electron irradiated areas are commensurate to that as catalysts for growing silicon nanowires, we have actually succeeded in growing silicon nanowires from the selectively grown gold particle via vapor liquid solid (VLS) mechanism using silane as source gas. The experimental results summarized above will be utilized for nanofabrication of semiconductor crystals by electron irradiation. Less