Adsorption and Thermal Decomposition Chemistry of 1-Propanol and Other Primary Alcohols on the Si(100) Surface

Abstract

The adsorption of several simple primary alcohols (1-propanol, ethanol, and methanol) on the Si(100)−(2 × 1) surface has been investigated using Auger electron spectroscopy (AES) and thermal desorption spectroscopy (TDS). These alcohols appear to undergo dissociative adsorption on this surface at room temperature. These results are in agreement with infrared and photoemission spectroscopic studies of ethanol and methanol adsorption. By comparison to the AES results from the adsorption of methyl iodide on Si(100), it was concluded that the surface saturation coverage of 1-propanol on Si(100) is slightly less than half a monolayer, identical (within experimental uncertainty) to the saturation coverages of ethanol and methanol. TDS reveals no parent desorption channels for all three of these molecules, and instead provides evidence for a β-hydrogen elimination channel of the surface-bound alkoxy radicals, as well as competing surface decomposition channels. To gain further physical insight into the available reaction pathways for these molecules on this surface, we have used ab initio and density functional theories to study adsorption on silicon clusters and found that the reaction paths obtained from this computational treatment are consistent with the experimental results.