FLOW-INJECTION SYSTEM FOR THE SCANNING TUNNELING MICROSCOPE

A flow injection scanning tunneling microscopy (FISTM) system is descr ibed and characterized which permits observation of surface chemical p rocesses. This modification to a standard scanning tunneling microscop e consists of a peristaltic pump attached via a manual HPLC-type flow injector to a constant-volume sample cell. Images recorded as fluids c ontinuously exchange in the cell are reported. Evidence supports that analytes are transported into the tip region through a stagnant fluid domain by diffusion from the adjacent, circulating bulk solution. Elec trochemical measurements of the exposed tip surface area and rates of diffusion of analytes are presented and interpreted. Erosion of contam inants on a gold surface exposed to hydrogen peroxide was observed usi ng FISTM, and these results are presented. (C) 1995 American Institute of Physics.