Adsorption and thermal decomposition of C2D5I on the (110) and (111) planes of NiAl: A temperature programmed deposition and x-ray photoelectron spectroscopy study

This study investigates the adsorption and the subsequent thermal decompois tion of d(5)-iodoethane (C2D5I) on the (110) and (111) planes of NiAl using temperature programmed desorption (TPD) and x-ray photoelectron spectrosco py (XPS). Both I 3 d(5/2) and C 1 s XPS data show that C2D5I adsorbs molecu larly on both NiAl surfaces at 120 K. Upon heating the sample, the C-I bond starts to cleave and the scission of this bond is complete on NiAl(110) an d NiAl(111) by 150 and 300 K, respectively. It is suspected that this cleav age results in the formation of C2D5(ad) and I-(ad). TPD results show that the thermal decomposition of C2D5(ad) yields C2D4 and D-2 as the main produ cts on both the surfaces. The main difference in the decomposition products of C2D5(ad) species on the two surfaces is that desorption of C2D4 occurs on NiAl(111) at similar to 315 K, similar to 50 K higher than the correspon ding value for NiAl(110). (C) 1999 American Vacuum Society. [S0734-2101(99) 00603-X].