Adsorption and thermal reaction of short-chain iodoalkanes on Ge(100)

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Title:	Adsorption and thermal reaction of short-chain iodoalkanes on Ge(100)
Authors:	Chuang, P.Y., Lee, W.L., Teng, T.F., Lai, Y.H., Hung, W.H.
Keywords:	Alkyl monolayers;Disproportionations;Ge surfaces;Ge(100);Hydride elimination;Iodoalkane;Temperature range;Thermal decompositions;Thermal reactions;Two-temperature;X ray photoelectron spectra
Date:	2010
Issue Date:	2013-05-21T09:08:41Z (UTC)
Publisher:	Department of Chemistry, Tunghai University
Abstract:	The adsorption and thermal decomposition of iodoalkanes CH 3I, C 2H 5I, and C 4H 9I on Ge(100) were studied with temperature-programmed desorption (TPD) and X-ray photoelectron spectra (XPS) using synchrotron radiation. At 105 K, the iodoalkanes adsorb both molecularly and dissociatively on Ge(100); the shorterchain iodoalkane dissociates to form a surface alkyl and an I adatom to a greater extent. The chemisorbed iodoalkane gradually dissociates to form a surface alkyl and an I adatom in a temperature range 200-370 K. At 720 K, most surface CH 3 desorbs directly from the surface, and other surface CH 3 radicals undergo disproportionation to desorb as CH 4. Surface C 2H 5 and C 4H 9 mostly undergo β-hydride elimination to desorb as C 2H 4 and C 4H 8 at ?550 K, respectively. The temperature for C 4H 9 to react is slightly lower than that for C 2H 5 because the C 4H 9 chain exhibits a stronger interaction with the surface than C 2H 5. The I adatom can react with a H atom liberated during decomposition of a surface alkyl and subsequently desorbs as molecular HI in two temperature regimes, ?650 and ?720 K. Some I adatoms are removed from the surface via direct desorption in atomic form at 720 K. On annealing to 770 K, the Ge surface becomes free of I adatom but retains a deposit of residual C as adatoms. According to our data, the temperature of fabrication and operation of a Ge-based device with the alkyl monolayer is suggested to be not higher than 530 K. ? 2009 American Chemical Society.
Relation:	Journal of Physical Chemistry C 113 (40) , pp. 17447-17454
Appears in Collections:	[化學系所] 期刊論文

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