AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThM

Paper EM-ThM3
Thermal Chemistry and Photochemistry of Organothiols Chemisorbed on GaAs(110)

Thursday, November 5, 1998, 9:00 am, Room 316

Session: Compound Semiconductor Surface Chemistry
Presenter: N. Camillone, III, Columbia University
Authors: N. Camillone, III, Columbia University
K.A. Khan, Columbia University
R.M. Osgood, Jr., Columbia University
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Self-assembled monolayers of organothiols and related compounds hold promise for use in the semiconductor industry as ultrathin electron beam resists, atomic-layer-epitaxy precursor layers, and monolayer adhesives. We have recently begun fundamental studies of the surface chemistry and photophysics of small organothiols [CH@sub 3@SH, (CH@sub 3@S)@sub 2@ and CH@sub 3@SCH@sub 3@] on GaAs. Temperature programmed desorption measurements indicate that each of these species interact strongly with the GaAs surface. The first monolayer of CH@sub 3@SH desorbs near 300 K, compared to approximately 100 K for the second layer, indicating a chemical interaction between the thiol and the surface, despite the fact that the molecule predominantly appears to desorb intact. The behavior of (CH@sub 3@S)@sub 2@ is quite different; the disulfide decomposes upon adsorption (or during the TPD temperature ramp) and desorbs predominantly as CH@sub 3@SCH@sub3@ at approximately 500 K, perhaps as the result of a concerted associative/dissociative desorption process which leaves sulfur at the surface. In addition, we will report on UV photoreaction cross section measurements and photoreaction products for these thiol, sulfide and disulfide compounds. For example, the measured cross section for photodissociation of an annealed (CH@sub 3@S)@sub 2@ monolayer at 193 nm is orders of magnitude smaller than that for CH@sub 3@SH.