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Open Access Nano Express

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

Tun-Wen Pi1*, Hsiao-Yu Lin2, Ya-Ting Liu2, Tsung-Da Lin3, Gunther K Wertheim4*, Jueinai Kwo2* and Minghwei Hong3*

Author Affiliations

1 National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan

2 Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan

3 Graduate Institute of Applied Physics and Department of Physics, National Taiwan University, Taipei 10617, Taiwan

4 Woodland Consulting, 175 Woodland Ave, Morristown, NJ, 07960, USA

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Nanoscale Research Letters 2013, 8:169  doi:10.1186/1556-276X-8-169

Published: 12 April 2013

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.

Keywords:
GaAs; Al2O3; Atomic layer deposition; Synchrotron radiation photoemission; 73.90. + f; 79.60.Jv