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Characterization of as‐grown and adsorbate‐covered N‐polar InN surfaces using in situ photoelectron spectroscopy
Author(s) -
Eisenhardt Anja,
Himmerlich Marcel,
Krischok Stefan
Publication year - 2012
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201100098
Subject(s) - x ray photoelectron spectroscopy , band bending , binding energy , materials science , molecular beam epitaxy , analytical chemistry (journal) , adsorption , epitaxy , ultraviolet photoelectron spectroscopy , valence (chemistry) , chemistry , nanotechnology , atomic physics , layer (electronics) , optoelectronics , nuclear magnetic resonance , physics , organic chemistry , chromatography
The surface electronic properties and adsorption behaviour of as‐grown and oxidized N‐polar InN films are characterized by photoelectron spectroscopy (XPS, UPS). The epitaxial growth of the InN layers was performed by plasma‐assisted molecular beam epitaxy on GaN/6H‐SiC(000‐1). After growth and in situ characterization the InN surfaces were exposed to molecular oxygen to evaluate the adsorption behaviour of O 2 on N‐polar InN and to study its impact on the surface electronic properties of the III‐nitride material. The results are compared with studies on In‐polar InN on GaN/sapphire templates. The as‐grown N‐polar InN surface exhibits a pronounced surface state at a binding energy of ∼1.6 eV. The valence band minimum lies about 0.8–1.0 eV below the surface Fermi level. Additionally, the XPS core level binding energies for InN(000‐1) are reduced compared to InN(0001) films, indicating different surface band bending for clean N‐polar and In‐polar InN, respectively. The interaction of molecular oxygen with the InN(000‐1) surface leads to a downward band bending by 0.1 eV compared to the initial state. Additional adsorption of species from the residual gas of the UHV chamber increases the surface downward band bending. Furthermore two pronounced oxygen related states with an energy distance of ∼5 eV could be detected in the valence band region. The adsorbed oxygen results in an additional component in the N1s core level spectra, which is interpreted as formation of NO x bonds.