Ultrahigh-vacuum multitechnique study of AuCN monolayers on Au(111) formed by electrochemical deposition

The two kinds of monolayers of AuCN electrodeposited on Au(111), indexed (1.15x root 3R-30 degrees) and (1.41x2 root 3R-30 degrees), have been subjected to x-ray and ultraviolet photoelectron spectroscopy (XPS, UPS) and high resolution electron energy loss spectroscopy (HREELS) as well as low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and scanning tunneling microscopy (STM) to determine the geometrical, electronic, and vibrational properties. The -AuCN- chain structure was taken into consideration. XPS yielded Au 4f signals from AuCN indicating fractional charges on the Au atom incorporated in AuCN. The UPS of AuCN/Au(111) was composed mainly of the Au orbitals with weak signals from CN orbitals, attributed by DV-X alpha relativistic molecular orbital calculation. By HREELS, the C-N stretching frequencies were found to be 2140-2160 cm(-1), which are consistent with the electronic structure. In the frequency region below 300 cm(-1), loss peaks related to the Au-N bonds were seen. The structures of -AuCN- chains in the (1.15x root 3R-30 degrees) and (1.41x2 root 3R-30 degrees) adlayers are discussed upon these new findings. (C) 2000 American Institute of Physics. [S0021-9606(00)70527-7].