AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA3
Reaction of Acetyl Chloride on Ge(100)-2x1: Formation of a Surface-bound Carbonyl

Tuesday, November 4, 2003, 2:40 pm, Room 328

Session: Organic Functionalization of Semiconductor Surfaces
Presenter: M.A. Filler, Stanford University
Authors: M.A. Filler, Stanford University
S.F. Bent, Stanford University
Correspondent: Click to Email
Since the introduction of vacuum-based organic functionalization of group-IV semiconductor surfaces, there has been considerable interest in attaching molecules beyond the initial monolayer. However, functional groups that are expected to be reactive in second layer reactions, such as amines and ketones, also react directly with the bare semiconductor surface. It is therefore necessary to protect these groups during the deposition of the initial layer or use a molecule where other pathways can kinetically compete and leave the reactive moiety intact. To this end, we have studied the reaction of acetyl chloride on Ge(100)-2x1 at 300K with infrared spectroscopy, temperature programmed desorption, and density functional theory. Infrared spectra show a strong @nu@(C=O) stretching peak near 1680 cm@super -1@ and no vibration modes in the @nu@(Ge-H) region indicating that Cl dissociation to produce a surface-bound carbonyl is the dominant reaction pathway. TPD results provide additional evidence of this surface product; ketene evolves near 525K while at higher temperatures H@sub 2@, HCl, and GeCl@sub 2@ desorb. DFT calculations predict that the barrier to Cl dissociation is only 1 kcal/mol above a chlorine dative-bonded state and is considerably smaller than that of any other reaction pathway. All of this data is strong evidence for a Cl dissociation reaction leaving a surface-bound carbonyl, which is expected to be more reactive toward second layer attachment chemistries and possibly enable layer-by-layer deposition of ultrathin organic films.