FACTS AND ARTIFACTS IN NEAR-FIELD OPTICAL MICROSCOPY

Near-field optical (NFO) microscopes with an auxiliary gap width regul ation (shear force, tunneling) may produce images that represent the p ath of the probe rather than optical properties of the sample. Experim ental and theoretical evidence leads us to the conclusion that many NF O results reported in the past might have been affected or even domina ted by the resulting artifact. The specifications derived from such re sults for the different types of NFO microscopes used therefore warran t reexamination. We show that the resolving power of aperture NFO micr oscopes, 30-50 nm, is of genuine NFO origin but can be heavily obscure d by the artifact. (C) 1997 American Institute of Physics.