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Modeling Growth Directional Features of Silicon Nanowires Obtained Using SiO T. Y. Tan, Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708-0300; S. T. Lee, Center Of Super-Diamond and Advanced Films (COSDAF) & Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, China; U. Gösele, Max-Planck-Institute of Microstructure Physics, Weinberg 2, D06120 Halle, Germany. ABSTRACT Silicon nanowires (SiNW) grown using Si monoxide source materials are mainly oriented in the direction, and some in the direction. These directional features may be understood by postulating that growth of the SiNW is governed by lateral advancement of {111} plane layers that are stepped, and the role of particular kinds of dislocations providing perpetuate steps. INTRODUCTION Semiconductor nanoclusters and nanowires have interesting electrical and optical properties. Among the various means of growing these materials, the vapor-liquid-solid (VLS) reaction [16], and the oxide-assisted (OA) method using unstable semiconductor-oxide source materials either by thermal evaporation or by laser ablation [7-13] produce nanowires in large quantities that are convenient for fundamental studies. A particular growth directional feature of the so-grown long semiconductor nanowires is well documented for the case of Si nanowires (SiNW): for VLS method the SiNW growth direction or its long dimension is [3,6], while for those obtained by the OA method this direction is primarily , sometimes also [9,13], see Fig. 1 for an example. In VLS growth, a metal (usually Au) is used as a catalyst, which appears as a small (molten) ball at the tip of the SiNW. This metal ball, super-saturated with Si atoms resulting from decomposition of the source materials SiCl4 or SiH4, renders the SiNW to grow rapidly. On the other hand, the OA SiNW is covered by a layer of oxide. In the OA cases, the supersaturation of Si atoms in the oxide is relatively low or moderate. In this paper we propose a model to explain the above mentioned SiNW growth directional features of the OA cases. MODELING OF SiNW GROWTH DIRECTIONAL FEATURES To explain the directional features of the OA cases, we use the postulates that: (i) a Si atom at a surface position is stable if it possesses two or more bonds, i.e., having two or more nearest neighbor atoms; (ii) growth of the SiNW is due to lateral advancement of {111} plane layers that are stepped at the growth front, and (iii) some dislocations will provide the growth front with perpetuate {111} layer steps. Postulate (i) is intuitively trivial. Postulate (ii) has been previously proposed by Csepregi et al. [14] to explain epitaxial Si growth rate dependence on wafer orientations of ion implantation induced amorphous Si layers. Postulate (iii) is classical in explaining whisker growth of metal and molecular crystals [15,16]. To use these postulates for the SiNW cases, they are further developed for the needed in-depth details. F8.38.1 Downloaded from https://www.cambridge.org/core