Add time:09/30/2019         Source:infona.pl

The influence of surface carbon on the formation of highly regular thin films of P-QUATERPHENYL (cas 135-70-6) (4P) grown on a Au(111) surface has been investigated in the mono- and multilayer regime by thermal desorption spectroscopy (TDS), X-ray photoelectron spectroscopy (XPS) and micro-channelplate low energy electron diffraction (MCP-LEED) under UHV conditions. A small carbon pre-coverage of 0.03 monolayers (ML) improves the surface mobility of adsorbed 4P molecules with respect to the clean surface by passivating Au surface defects. This enables a highly crystalline 4P film growth even at a low substrate temperature of 93K. Otherwise, the thermodynamically stable monolayer structure is identical to that on the C-free surface, namely consisting of alternating edge/face packed, lying molecules. The structure of the first 4P monolayer grown on a 0.15ML C covered Au(111) surface is different. Only edge-on oriented molecules accommodate in the corresponding surface unit cell. At a C coverage of 0.5ML the first 4P monolayer is disordered, whereas for higher coverages a highly crystalline structure with upright standing molecules is adopted. Depending on the substrate temperature during film growth the surface carbon causes a different wetting behaviour of the 4P films, resulting in a different mesoscopic film morphology.

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