A model for growth directional features in silicon nanowires

Long silicon nanowires (SiNWs) grown by laser ablation or by thermal evaporation of monoxide source materials are primarily oriented in the <112> direction, and some in the <110> direction, but rarely in the <100> or <111> directions. We propose a model to explain these SiNW growth directional features. The model consists of two parts. Part one is concerned with mechanism-based criteria and part two with applying these criteria to explain the experimental results. Four criteria are considered: (i) the stability of a Si atom occupying a surface site; (ii) the Si {111}ace stability in the presence of oxygen; (iii) the stepped Si {111} surface layer lateral growth process; and (iv) the effect of dislocations in providing perpetuating {111} steps to facilitate SiNW growth. Analyses of SiNW growth in accordance with these criteria showed that <112> and <110> are the preferred SiNW growth directions, and that <111> and <100> are not.