title: Atom-to-atom interactions for atomic layer deposition of trimethylaluminum on Ga-rich GaAs(001)-4 × 6 and As-rich GaAs(001)-2 × 4 surfaces: a synchrotron radiation photoemission study.
abstract: High-resolution synchrotron radiation photoemission was employed to study the effects of atomic-layer-deposited trimethylaluminum (TMA) and water on Ga-rich GaAs(001)-4 × 6 and As-rich GaAs(001)-2 × 4 surfaces. No high charge states were found in either As 3d or Ga 3d core-level spectra before and after the deposition of the precursors. TMA adsorption does not disrupt the GaAs surface structure. For the (4 × 6) surface, the TMA precursor existed in both chemisorbed and physisorbed forms. In the former, TMA has lost a methyl group and is bonded to the As of the As-Ga dimer. Upon water purge, the dimethylaluminum-As group was etched off, allowing the now exposed Ga to bond with oxygen. Water also changed the physisorbed TMA into the As-O-Al(CH3)2 configuration. This configuration was also found in 1 cycle of TMA and water exposure of the (2 × 4) surface, but with a greater strength, accounting for the high interface defect density in the mid-gap region.
authors.affiliation: National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan. pi@nsrrc.org.tw.
authors.forename: Tun-Wen
authors.initials: TW
authors.lastname: Pi
authors.forename: Hsiao-Yu
authors.initials: HY
authors.lastname: Lin
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Liu
authors.forename: Tsung-Da
authors.initials: TD
authors.lastname: Lin
authors.forename: Gunther K
authors.initials: GK
authors.lastname: Wertheim
authors.forename: Jueinai
authors.initials: J
authors.lastname: Kwo
authors.forename: Minghwei
authors.initials: M
authors.lastname: Hong