Abstract
At atmospheric pressure, semiconductor silicon (Si-I) has the stable diamond structure. Under hydrostatic pressures of 11~12 GPa, the Si-I phase undergoes a phase transformation to the phase, which has a β-tin structure. During the release of pressure, metastable phases semi-metallic Si-III, semiconductive Si-XII and amorphous silicon are produced from Si-II at different unloading rates. Although most experimental results reveal various properties of phases, less informations about the nanoscale properties have been explored.In the experiment, conducting atomic force microscopy is used to study the high conductivity Si-III phase under nanoindentation. With loading forces of 3~90 mN, discontinuities in the load-displacement curves are observed, which are caused by the volume expansion effect when the Si-III and Si-XII phases are produced. In the simultaneously obtained topography and current images, high current regions are found to be randomly distributed in the indented region. These regions have sizes ranging from several tens to several hundreds of nm with a smallest diameter of around 25 nm. Current-voltage curves in the high current site have also been measured and fitted with Fowler-Nordheim equation. Barrier height between Si-III and SiO2 and work function of Si-III were determined to be 0.39 and 1.51 eV, respectively.