Synthesis and postgrowth doping of silicon nanowires

Abstract

High-quality silicon nanowires (SiNWs) were synthesized via a thermal evaporation method without the use of catalysts. Scanning electron microscopy and transmission electron microscopy showed that SiNWs were long and straight crystalline silicon with an oxide sheath. Field effect transistors were fabricated to investigate the electrical transport properties. Devices on as-grown material were p-channel with channel mobilities 1–10cm2V−1s−1. Postgrowth vapor doping with bismuth converted these to n-channel behavior.

Applications of electron microscopy to the characterization of semiconductor nanowires

“…The details of VS type growth are still not well understood; however under certain conditions epitaxial growth may also occur [18,19]. Using this method we have successfully grown nanowires of β-Ga 2 O 3 (unpublished), Si [20] and GaN [21].…”

“…2. The morphological details of each nanostructure can be appreciated from the insets, chemical maps for crystalline Si and amorphous SiO 2 obtained using energy-filtered TEM (EFTEM) [20]. These clearly reveal that the nanowire in the upper left corner is in fact a Si/SiO x core-sheath structure, in contrast to the nanochain (center left) is primarily SiO x .…”

“…Planar defects are also common in our Si nanowires [20], and these are {111} type twins that run obliquely across the nanowire (see arrowed feature in Fig. 5a) but never along the nanowires.…”

“…Our VS-grown Si nanowires [20] were mostly grown along the commonly reported <111> and <211> directions [25,35,36]. Figure 5a shows a typical VS-grown Si nanowire, with a ~15 nm diameter crystalline Si core sheathed with ~10 nm of amorphous oxide.…”

“…We have successfully demonstrated that dielectrophoretic assembly is a viable technique to assemble β-Ga 2 O 3 nanowire arrays (unpublished data). We used lithographic contact patterning to fashion Si nanowire FETs and were able to modulate the electrical characteristics of the fabricated Si nanowire FETs from p-to n-type via post-growth doping [20].…”