ASSESSMENT OF NSOM RESOLUTION ON III-V SEMICONDUCTOR THIN-FILMS

Emission-mode aperture near-field scanning optical microscopy (NSOM) i s applied to semiconductor thin films for resolution assessment and ar tifact investigation purposes. We have used GaAs thin films deposited on GaP(111) substrates with A and B polarities by metal organic vapour phase epitaxy (MOVPE). Optical discrimination of GaAs islands on GaP( 111) has been accomplished with a lateral resolution better than 20 nm (lambda/35) in the transmission mode. These samples have proven valua ble for inspection of contrast mechanisms, based on discrimination of materials having different refractive index and absorption coefficient s, as well as investigation of topography and shadowing artifacts in o ptical near-field imaging.