Ultrahigh-vacuum multitechnique study of AuCN monolayers on Au(111) formedby 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 subject ed 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 scanni ng tunneling microscopy (STM) to determine the geometrical, electronic, and vibrational properties. The -AuCN- chain structure was taken into consider ation. 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 mai nly of the Au orbitals with weak signals from CN orbitals, attributed by DV -X alpha relativistic molecular orbital calculation. By HREELS, the C-N str etching frequencies were found to be 2140-2160 cm(-1), which are consistent with the electronic structure. In the frequency region below 300 cm(-1), l oss peaks related to the Au-N bonds were seen. The structures of -AuCN- cha ins in the (1.15x root 3R-30 degrees) and (1.41x2 root 3R-30 degrees) adlay ers are discussed upon these new findings. (C) 2000 American Institute of P hysics. [S0021-9606(00)70527-7].