Size-controlled percolation pathways for electrical conduction in porous silicon

摘要: Silicon shows photo- and electroluminescence at visible wavelengths when chemically etched into a microporous network of ‘wires’ several nanometres thick1. This raises the possibility silicon-based optoelectronic technology. The luminescence properties may be understood on basis injection or creation electrons holes in interconnected wires which recombine radiatively with high efficiency1,2. Elucidating electron-transport mechanisms has been held back by difficulties, particularly that making stable, high-quality contacts to porous material. Here we report experiments probe conduction process using photoemission stimulated hard-ultraviolet/X-ray synchrotron radiation, obviating need for good electrical contacts. We find conductivity silicon films is temperature-dependent, become insulating low temperatures. suggest these results terms percolation occurring through sites thermally activated, postulate this activation consequence Coulomb blockade effect3,4 nanoscale channels film. consistent our observation optical ‘unblocking’ conducting pathways. These imply size distribution nanowires backbone plays key role determining properties, porous-silicon light-emitting diodes use only small (and least efficient) fraction Improvements efficiency possible taking account percolative nature process.