Adsorption chemistry of cyanogen bromine and cyanogen chlorine on silicon(100)

The adsorption and decomposition of cyanogen halides, XCN (X = Br, Cl), on Si(100) is investigated utilizing X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). For submonolayer exposures, XPS indicates that the CN triple bond of XCN remains intact upon adsorption at 100 K. The UPS spectrum contains two peaks assigned to the π-electrons in the CN triple bond. The splitting indicates that some fraction of the XCN molecules adsorbs molecularly at low temperature. XPS analyses of the C 1s photoelectron peak following submonolayer exposure at low temperature suggest a greater fraction of BrCN (60%) adsorbs molecularly than ClCN (40%). XPS and UPS measurements at room temperature show that the X−CN bond breaks, while the CN bond remains intact during room-temperature adsorption on Si(100). Thus, the UPS spectrum of XCN adsorbed at room temperature on Si(100) contains a peak at 6.0 eV due to the unperturbed π electrons of the CN species. Upon annealing a CN-saturated Si(100)...