MODEL FOR SCANNING TUNNELING OPTICAL MICROSCOPY - A MICROSCOPIC SELF-CONSISTENT APPROACH

A general method based on a microscopic picture of matter is developed in order to describe the optical interaction between a thin dielectric tip and a corrugated sample lighted in total reflection. Such a model is expected to interpret recent images obtained from scanning tunneling optical microscopy (steps, infinite tracks, glass plate with local scratches). The conversion of evanescent waves into homogeneous propagating ones is studied from a molecular-physics perspective (multipolar interactions between each atom of the tip and of the object). Our approach is concerned with the study of subwavelength details lying at the surface of a transparent medium. So, instead of solving the macroscopic Maxwell equations and applying the corresponding boundary conditions at the surface of the tip and of the object, we prefer a microscopic treatment in which the dielectric surrounding is taken into account from a set of dynamical matrices introducing all correlations between each elementary volume inside the object. Relations with experiments are discussed. © 1990 The American Physical Society.