Carbonyl mediated attachment to silicon: Acetaldehyde on Si(001)

摘要

A detailed understanding of the chemical reactions of organic molecules with semiconductor surfaces will greatly aid schemes for the incorporation of organic functionality into existingtechnologies. In this paper we report on the reaction of acetaldehyde (CH3CHO) with silicon (001) as revealed by a combination of temperature-dependent scanning tunneling microscopy (STM)experiments and density functional theory (DFT). We observe that low-coverage exposures at room temperature result almost exclusively in the formation of a single adsorbate species. Conversion ofthis structure into thermodynamically favored bridge-bonded structures is achieved through temperature anneals between 150-250℃. We determine the chemical identity of each of theexperimentally observed species by comparison with DFT total energy calculations and simulated STM images. Calculations of transition states are used to formulate a full reaction pathwayexplaining the formation of the observed species. Excellent agreement is found between our experimental measurements and theoretical calculations. The results also present a picture consistentwith our previous work on acetone and reveal a general reaction pattern for molecules containing the acetyl COCH_3functional group, where the initial attachment to surface is mediated by acarbonyl C=0 group. This suggests that modification of the residue R will facilitate in binding otherelectronically active molecules to the surface in a controlled fashion.