A variable cryogenic temperature near-field scanning optical microscope

We describe a novel variable (cryogenic) temperature near-field scanning optical microscope (VT-NSOM) designed specifically for submicron imaging of materials and devices over a temperature range of 12-300 K. In high vacuum, we cool only the sample stage of the compact NSOM, thereby maintaining a large scan area (35 mu m x 35 mu m) at low temperatures and enabling rapid (similar to 30 min) temperature changes. With incorporation into an external conventional optical microscope, the VT-NSOM is capable of imaging a single submicron feature over the entire temperature range. We demonstrate the performance of the instrument by examining the photoresponse of threading dislocation defects in relaxed GeSi films. (C) 1999 American Institute of Physics. [S0034-6748(99)00908-9].