Palladium Thin-Films on Clean and Hydrogen-Terminated Si(110): The Effect of Hydrogen Termination on Metal Adsorption

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A combined scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED) study of the room-temperature deposition of palladium on wet-chemically-prepared H/Si(110) and vacuum-prepared Si(110) “$16{\times}2$” was carried out to gauge the ability of a hydrogen barrier layer to restrict reactive adsorption of Pd on Si(110) (e.g. silicide formation) and to determine the effect of the hydrogen barrier layer on the growth mode of the deposited films. For deposition quantities less than 1.5 monolayers (ML), Pd atoms adsorbed in a random fashion on the clean Si(110) surface, while islands formed on the H/Si(110) surface. However, after ${\sim}3$ ML of deposition the film morphology took on a disordered hillock motif for both clean and hydrogen-terminated substrates. The size distribution of the hillocks was remarkably narrow, and indistinguishable for clean and hydrogen terminated substrates. Further, the hillock morphology was invariant with Pd deposition between 3 and ${\sim}8$ ML. XPS analysis revealed the deposited films to be chemically similar to Pd2Si for both Si(110) “$16{\times}2$”, and H/Si(110) substrates, indicating that the hydrogen barrier layer does not prevent silicide formation.
2009-08-25