Near-field surface photovoltage

A phenomenon called near-field surface photovoltage is presented. It is bas ed on inducing photovoltage only at a semiconductor space-charge region usi ng near-field illumination. The photovoltage is obtained by measuring the c ontact potential difference between an optical near-field force sensor and a semiconductor surface under illumination. It is shown that the near-field illumination induces photovoltage at the surface which is principally diff erent from photovoltage induced by far-field illumination. The mechanisms t hat govern the different far-field and near-field photovoltage response are discussed. (C) 2000 American Institute of Physics. [S0003- 6951(00)04132-2 ].