AVS 49th International Symposium
    Surface Science Thursday Sessions
       Session SS+EL+OF-ThM

Paper SS+EL+OF-ThM9
Adsorption Chemistry of Cyanogen Bromide and Iodide on Silicon (100)

Thursday, November 7, 2002, 11:00 am, Room C-112C

Session: Reactions and Patterning of Organics on Silicon
Presenter: N.F. Materer, Oklahoma State University
Authors: N.F. Materer, Oklahoma State University
P. Rajasekar, Oklahoma State University
E.B. Kadossov, Oklahoma State University
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The adsorption of cyanogen iodide (ICN) and bromide (BrCN)on a silicon (100) surface is studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and thermal desorption spectroscopy (TPD). After submonolayer exposures, XPS indicates that the CN triple bond of both ICN and BrCN emains intact upon adsorption at 100K. The UPS spectrum of these molecules contains two peaks assigned to the pi electrons in the CN triple bond. The splitting of these levels, due to the interaction between the pi electrons on the cyanogen and the halide, show that some portion of the initially adsorbed cyanogens halide also remains intact upon low temperatures adsorption. In contrast, the UPS spectrum of ICN and BrCN adsorbed at room temperature on Si(100) contains only one peak due to the pi electrons in the carbon nitrogen triple bond. The lack of splitting in the room temperature UPS spectrum is a result of XC (X=Br, I) bond dissociation. Thus, the XC bonds breaks while the CN bond remains intact during room temperature adsorption on Si(100). Upon annealing the Si(100) surface to higher temperatures, the UPS spectra indicates that the C-N triple bond remains intact until approximately 700 K. Simultaneous changes in the C 1s photoelectron peak are consistent with the idea that C-N bond cleavage in the cyanogen halides is correlated with silicon carbide formation.