Thermal Transformation of 4,4"-Diamino-p-terphenyl on a Si(111)-7 x 7 Surface Analyzed by X-ray Photoemission Spectroscopy and Scanning Tunneling Microscopy

Analysis using X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM) was carried out for 4,4 diamino-p- terphenyl (DAT) deposited on a Si(111)-7 * 7 surface with a low coverage at room temperature adn subsequently heated at temperature from 300 to 800 degrees C. The XPS analysis showed that nitrogen atoms in amingo groups of DAT partly reacted wit the Si at 350 degrees C and were transformed to silicon nitride at 600 degrees C while caron atoms in phenyl rings of DAT partly reacted with the Si at 600 degrees C. The aggregations were found after being heated at 800 degrees C by STM observation and were attributed to silicon carbide and silicon nitride with carbon atoms in the phenyl rings out of DAT by XPS analysis. The XPS and STM combined analysis revealed the critical temperatures of decompostion and transformation of molecules on substrates with their arrangement and chemcial states at a molecular level.