Scanning tunneling microscopy in air and liquid

In air, atomic images in three different grades of graphite crystals have been investigated with an STM. In the ordered regions, single-crystal flake graphite (Kish graphite) showed an anomalously large atomic corrugation Δ Z and a small ratio of the tunneling current modulation Δ I T /⟨ I T ⟩ compared with those of highly oriented pyrolytic graphite (HOPG). In disordered regions, the Kish graphite and HOPG showed occasionally novel super-structures near defects, whereas pyrolytic graphite (PG) showed random atomic images frequently. In liquid, an electrochemically treated surface of a polycrystalline silver electrode in solution has been investigated with an STM where an electrochemical cell was mounted on the sample stage for in-situ STM measurements. Localized electrochemical reactions were found in a specific area of the topographic image as large asymmetric spikes which were also observed as time-resolved asymmetric current-spikes.