Nanoscale elemental identification by synchrotron‐radiation‐based scanning tunneling microscopy

Abstract

Abstract Scanning tunneling microscopy (STM) combined with synchrotron radiation (SR) enabled elemental analysis on solid surfaces at an anometer scale. The principle of analysis is based on the inner‐shell excitation of a specific energy level under STM observation. After first demonstrative results on a semiconductor heterointerface (Ge nanoisland on an Si(111) 7 × 7 surface), a second trial of nanoscale elemental analysis by the SR‐STM system was accomplished for Cu nanodomains on a Ge(111) 2 × 8 surface. A key to achieve successful results is to effectively increase the signal to noise (S/N) ratio and to extract the element‐specific modulation of the tunneling current, which is derived from the inner‐shell excitation. An essential point for signal detection with a high S/N ratio is to construct a total system including lock‐in amplifier with an optical chopper for high accuracy, and a real‐time control system to check the incident‐beam condition by observing the beam‐induced current profiles. Using these techniques, it has been shown that the SR‐STM system provides new possibilities forn anoscale surface analysis. Copyright © 2008 John Wiley & Sons, Ltd.