Well controlled assembly of silicon nanowires by nanowire transfer method

Efforts to date in silicon nanowire research have primarily focused on the nanowire synthesis and the demonstration of individual nanowire-based devices exhibiting interdisciplinary potential spanned from electrical ( Duan et al 2003 Nature 425 274-8; Cui and Lieber 2001 Science 291 851-3; Morales and Lieber 1998 Science 279 208-11) through biomedical applications ( Cui et al 2003 Science 293 1289-92; Zheng et al 2005 Nature Biotechnol. 23 1294-301). However, the realization of integrated nanowire devices requires well ordered assembly of a silicon nanowire ( Huang et al 2001 Science 291 630-3; Whang et al 2003 Nano Lett. 3 1255-9) as well as simple and cost effective fabrication. Here we describe a simple fabrication scheme and a large-scale assembly of silicon nanowires by combining top-down fabrication with nanowire transfer onto another insulator substrate for device manufacture. Our innovative fabrication method enables us to obtain well defined silicon nanowires as a freestanding bridge structure with a diameter of 20-200 nm and a length varying from 5 to 100 mu m using micro-machining processes. Direct transfer of the freestanding nanowires simply provides large-scale assembly of silicon nanowire on various substrates for highly integrated devices such as high-performance thin-film transistors (TFTs) ( Duan et al 2003 Nature 425 274-8; Ishihara et al 2003 Thin Solid Films 427 77-85) and nanowire-based electronics ( Cui and Lieber 2001 Science 291 851-3). Electrical transport properties of the transferred silicon nanowire were also investigated.