Near-field optical-scanning microscopy

Near-field optical-scanning (NFOS) microscopy or]] optical stethoscopy" provides images with resolution in the 20-nm range, i.e., a very small fraction of an optical wavelength. Scan images of metal films with fine structures presented in this paper convincingly demonstrate this resolution capability. Design of an NFOS microscope with tunnel distance regulation, its theoretical background, application potential, and limitations are discussed.