STM INVESTIGATIONS OF SOLID-SURFACES IN WATER AND AIR

Scanning tunneling microscopy (STM) investigations on nonplanar surfac e elements of different specimen materials are carried out in atmosphe ric air and when they are covered with distilled water in order to det ermine effects of water on the recorded surface topography and the tun neling barrier. When water is supplied to a dry specimen surface small scale topographic irregularities (up to about 0.2 mum) are found to b e smoothed and characteristic changes are observed in the tunneling ba rrier signals of the investigated materials. The observed topographic changes in water are expected to be caused by nano-voids formed by det achment of the liquid from concave surface elements. During scanning t he STM tips were found to be worn, particularly when scanning in air o n some of the non-noble metals, much less in water. As wear affects th e resolution of the STM it may be an advantage to scan in water instea d of in air if locally the specimen has a poor conductivity, but the p ossibility that the recorded interface topography is affected by the w ater must be taken into consideration. Further, the level of the tunne ling barrier signals of different materials and their change at exposu re to water instead of air can be used for detecting nucleation of sur face coatings.