Nature of the Band Gap of In 2 O 3 Revealed by First-Principles Calculations and X-Ray Spectroscopy

Bulk and surface sensitive x-ray spectroscopic techniques are applied in tandem to show that the valence band edge for In2O3 is found significantly closer to the bottom of the conduction band than expected on the basis of the widely quoted bulk band gap of 3.75 eV. First-principles theory shows that the upper valence bands of In2O3 exhibit a small dispersion and the conduction band minimum is positioned at Gamma. However, direct optical transitions give a minimal dipole intensity until 0.8 eV below the valence band maximum. The results set an upper limit on the fundamental band gap of 2.9 eV.

• UD
  U.S. Department of Energy

  Awards: DE-FG02-98ER45680, AC02-98CH10886, DE-AC02, DE-FG02-, DE-AC36-99GO10337, DE-FG02, DE-AC02-, FG02-98ER45680
• DA
  Deutscher Akademischer Austauschdienst
• DF
  Deutsche Forschungsgemeinschaft

  Awards: KL1225/4, SFB 595
• AC
  American Chemical Society Petroleum Research Fund
• EA
  Engineering and Physical Sciences Research Council

  Awards: DE-AC02-98CH10886, EP/E025722/1
• AR
  Army Research Office
• BN
  Brookhaven National Laboratory

  Awards: DE-AC02-98CH10886, AC02-98CH10886