Scanning tunneling microscopy of silver and gold metal liquidlike films

Abstract

Metal liquidlike films (MELLFs) are formed when an aqueous colloidal metal suspension is in contact with an immiscible organic liquid phase. That the major constituent of the films is metal is evident from their metallic luster and high reflectivity. They can easily flow, support hydrodynamic waves, and generally do not tear upon insertion of objects through them. They thus exhibit the rheological properties of liquids. They do not, however, conduct. These films have been lifted onto an atomically flat gold substrate and examined with a scanning tunneling microscope. The very high vertical resolution of this instrument provides a unique insight into the shape of the deposited metal particles. On silver MELLFs two types of features are consistently observed: long, slablike features with flat faces of width ∼500 Å, and spheroid features of similar lateral dimension, some of which also exhibit flat facets (smooth to within 10 Å). Only the latter type of feature has been observed on gold MELLFs, but the lateral dimensions are smaller, approximately 200 Å. The dimensions of the spheroidal particles are confirmed by both transmission electron microscopy and atomic force microscopy.