Adsorption of CO, O2, and H2O on GaAs(100): Photoreflectance Studies

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Adsorption of CO, 02, and H2O on semi-insulating GaAs(l00) has been examined with photoreflectance (PR). This work represents the first use of PR for quantitative adsorption measurements on semiconductors. In PR, the laser-induced change in surface reflectance is monitored as a function of wavelength. The resulting spectra are sensitive to changes in both the surface potential and the nature of surface states. Results at the E1(3.0 eV) and E0(1.4 eV) transitions are complementary to each other. Sticking coefficients S were obtained from E1data for these gases, and S at low coverage was found to increase in the order CO<O2<H2O. S decreases by at least four orders of magnitude for all the gases as saturation is approached. The results suggest that oxygen has two binding states that fill sequentially. Gas adsorption generally improves the communication between isolated surface states and the bulk.

Original languageEnglish (US)
Pages (from-to)3279-3286
Number of pages8
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Issue number6
StatePublished - Nov 1989

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films


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