{Reference Type}: Journal Article {Title}: Distance dependence of atomic-resolution near-field imaging on α-Al2O3 (0001) surface with respect to surface photovoltage of silicon probe tip {Author}: Yamanishi, Junsuke; Tokuyama, Takashi; Naitoh, Yoshitaka; Li, Yan Jun; Yasuhiro, Sugawara {Journal}: Nano Research {ISBN/ISSN}: 1998-0124 {Year}: 2016 {Volume}: 9 {Issue}: 2 {Pages}: 530-536 {DOI}: 10.1007/s12274-015-0934-4 {Keywords}: near-field scanning optical microscopy {Keywords}: near field {Keywords}: surface photovoltage {Keywords}: α-Al2O3 (0001) {Keywords}: force detection {Abstract}: Recently, we achieved atomic-resolution optical imaging with near-field scanning optical microscopy using photon-induced force detection. In this technique, the surface photovoltage of the silicon-tip apex induced by the optical near field on the surface is measured as the electrostatic force. We demonstrated atomicresolution imaging of the near field on the α-Al2O3 (0001) surface of a prism. We investigated the spatial distribution of the near field by scanning at different tip-sample distances and found that the atomic corrugation of the near-field signal was observed at greater distances than that of the atomic force microscopy signal. As the tip-sample distance increased, the normalized signal-to-noise ratio of the near field is in a gradual decline almost twice that of the frequency shift (Δf). {URL}: https://www.sciopen.com/article/10.1007/s12274-015-0934-4 {Language}: en