Properties of ambient air aged thin porous silicon

Thin porous silicon (PS) exhibits the red and blue luminescence bands without any rapid thermal oxidation. In addition, ambient air aged thin PS displays the increase of blue photoluminescence (PL) band with the reduction of the red PL band. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) have been performed both on freshly prepared and ambient air aged anodically etched PS samples. STM studies of these samples reveal the porous structure and displays less than 5 nm feature size for visible luminescing samples. STS analysis of freshly prepared PS shows the expected increase in band-gap energy compared with unetched silicon. The ambient air aged PS which exhibits both red and blue PL reveals an electronic structure similar to that obtained from STS.