Fabrication of Crystalline Semiconductor Nanowires by Vapor-Liquid-Solid Glancing Angle Deposition (VLS-GLAD) Technique
Materials Research Society Symposium Proceedings
Vapor-liquid-solid (VLS) method has become one of the few and most powerful bottomup single crystal nanowire growth techniques in nanotechnology due to its easy scalability from micro to nano feature sizes, high throughput, relatively low cost, and its applicability to various semiconductor materials. On the other hand, control of growth direction and crystal orientation of nanowires, which determine their electrical, optical, and mechanical properties, stand as major issues in VLS technique.
... this study, we demonstrate new vapor-liquid-solid glancing angle deposition (VLS-GLAD) fabrication approach to make well-ordered arrays of crystalline semiconductor nanowires with controlled geometry. VLS-GLAD is a physical vapor deposition based method and utilizes selective deposition of source atoms onto metal catalyst nanoislands placed on a crystal wafer. VLS-GLAD incorporates an obliquely incident flux of source atoms and selective deposition on catalyst islands is achieved by "shadowing effect". This geometrical process combined with conventional VLS growth mechanism leads to growth of crystalline semiconductor nanowire arrays tilted towards the incoming flux. In this study, we report morphological and structural properties of tilted single crystal germanium nanowire arrays fabricated by using conventional thermal evaporation system. In addition to the tilted geometry, by introducing substrate rotation, nanowires with various morphologies including helical, zigzag, or vertical shapes can be fabricated. Engineering crystalline nanowire morphology by using VLS-GLAD have the potential of enabling control of optical, electrical, and mechanical properties of these nanostructures leading to the development of novel 3D nano-devices.