Charge transfer on porous silicon membranes studied by current-sensing atomic force microscopy

A visible rectification effect on the current-voltage curves of metal/porous silicon/p-silicon has been observed by currentsensing atomic force microscopy.The current-voltage curves of porous silicon membranes with different porosities,prepared through variation of etching current density for a constant time,indicate that a higher porosity results in a higher resistance and thus a lower rectification,until the current reaches a threshold at a porosity＞55%.We propose that the conductance mode in the porous silicon membrane with porosities＞55% is mainly a hopping mechanism between nano-crystallites and an inverse static electric field between the porous silicon and p-Si interface blocks the electron injection from porous silicon to p-Si,but with porosities ＜55%,electron flows through a direct continuous channel between nano-crystallites.