Scanning tunneling microscopy for the study of the synchrotron-radiation stimulated processes; Synchrotron-radiation stimulated desorption of SiO2 films on Si(111) surface

We have constructed a scanning tunneling microscopy (STM) system for the st udy of synchrotron radiation (SR) stimulated photochemical reactions. In or der to eliminate the vibration and acoustic noise, the entire UHV chamber i s mounted on a high-performance air-suspended vibration isolation table and was also covered by the soundproof mat. The mechanisms for SR stimulated d esorption of SiO2 thin films on the Si(lll) surfaces have been investigated using the STM, low energy electron diffraction (LEED), and Auger electron spectroscopy. An atomically flat and clean Si(lll)-(7x7) surface was obtain ed after two hours SR irradiation at a surface temperature of 700 degrees C . The STM topograph suggests that the desorption mechanism may be completel y different between thermal and SR stimulated desorption of SiO2 film.