کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5424485 | 1395826 | 2008 | 8 صفحه PDF | دانلود رایگان |
We report experiments performed on vacuum deposited perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) films on Ag(1Â 0Â 0) by spot profile analysis low energy electron diffraction (SPA-LEED) and scanning tunnelling microscopy (STM). Up to a coverage of 1Â ML, PTCDA forms a commensurate c(8Â ÃÂ 8) structure with two molecules per primitive unit cell, which are perpendicularly oriented to each other (four molecules per c(8Â ÃÂ 8) unit cell). The PTCDA islands exhibit an equilibrium shape that corresponds to the symmetry of the Ag(1Â 0Â 0) surface. The structural order is stable up to a temperature of â¼670Â K, at which a phase transition to a disordered phase occurs. Upon cooling back to room temperature, the order is partly re-obtained, although there is evidence that molecules have partly desorbed and dissociated at the high temperature. At coverages above 1Â ML, a second layer orders in a herringbone structure on top of the c(8Â ÃÂ 8)-ordered first layer. The corresponding unit cell is very similar to that of the (1Â 0Â 2) plane of PTCDA bulk crystals.
Journal: Surface Science - Volume 602, Issue 12, 15 June 2008, Pages 2061-2068