کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5423823 | 1395803 | 2009 | 4 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Structural evolution of sulfur overlayers on Pd(1Â 1Â 1)
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
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چکیده انگلیسی
Low energy ion scattering spectroscopy (LEISS) has been used to characterize the evolution of ordered structures of S on the Pd(1Â 1Â 1) surface during annealing. During exposure of the Pd(1Â 1Â 1) surface to 0.7Â L H2S at 300Â K-conditions that produce the S(â3Â ÃÂ â3)R30 overlayer-the intensity of the Pd LEIS signal decreases and a feature assigned to adsorbed S appears as the adsorbed layer forms. When the surface is held at 300Â K after exposure to H2S is stopped, the LEIS Pd intensity partially recovers and the S signal weakens, presumably as surface S atoms assume their equilibrium positions in the S(â3Â ÃÂ â3)R30 overlayer. Subsequent annealing of the S(â3Â ÃÂ â3)R30 structure at 700Â K causes it to convert into a S(â7Â ÃÂ â7)R19 overlayer, whose LEIS spectrum is identical to that of clean Pd(1Â 1Â 1). The absence of LEIS evidence for S atoms at the exposed surface of the S(â7Â ÃÂ â7)R19 overlayer is at odds with published models of a mixed Pd-S top layer. Despite the similarity of the LEIS spectra of Pd(1Â 1Â 1) and Pd(1Â 1Â 1)-S(â7Â ÃÂ â7)R19, their activities for dissociative hydrogen adsorption are very different-the former readily adsorbs hydrogen at 100Â K, while the latter does not-suggesting that S exerts its influence on surface chemistry from subsurface locations.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Surface Science - Volume 603, Issue 13, 1 July 2009, Pages L82-L85
Journal: Surface Science - Volume 603, Issue 13, 1 July 2009, Pages L82-L85
نویسندگان
James B. Miller, Andrew J. Gellman,