کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5424386 | 1395822 | 2008 | 7 صفحه PDF | دانلود رایگان |
Surface structures and related electronic properties of flat Co nanoislands supported on Cu(1Â 1Â 1) are studied before and after adsorbing different doses of molecular hydrogen at 10Â K by low-temperature scanning tunneling microscopy/spectroscopy (STM/STS) at 5Â K. It is found that the adsorption process on Co consists in two steps. First, H2 dissociatively chemisorbs on Co forming an atomic H adlayer. Subsequently, molecules impinging on that H-terminated Co surface are physisorbed. When adsorbing a low dose of hydrogen on the Co/Cu(1Â 1Â 1) system, STM analysis shows that the chemisorbed hydrogen adlayer on Co forms a p(2Ã2) superstructure. On Cu surface however, no superstructure is observed. When adsorbing a high dose of H2, hydrogen-induced superstructures are observed on both Co and Cu surfaces. These superstructures are ascribed to the presence of physisorbed molecules as revealed by the STS spectra. A (3Ã3) superstructure is observed on Co and a mixture of (2Ã2) and (3Ã3) is identified on Cu. A model describing the adsorption sites of molecules is proposed: H2 molecules occupy on-top sites when arranged as a (2Ã2) phase and they occupy on-top and bridge sites when arranged as a (3Ã3) phase. Besides, STM-induced desorption is used to desorb atomic hydrogen from selected Co nanoisland surface. The desorption is visualized in terms of a disappearance of the p(2Ã2) superstructure.
Journal: Surface Science - Volume 602, Issue 24, 15 December 2008, Pages 3667-3673