Photoelectron emission yield experiments on evolution of sub-gap states in amorphous In-Ga-Zn-O thin films with post deposition hydrogen treatment

Total photoyield emission spectroscopy (TPYS) was applied to study the evolution of sub-gap states in hydrogen-treated amorphous In-Ga-Zn-O (a-IGZO) thin films. The a-IGZO thin films were subjected to hydrogen radicals and subsequently annealed in ultra-high vacuum (UHV) conditions. A clear onset of...

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Bibliographic Details
Published in:Applied physics letters 2015-09, Vol.107 (11)
Main Authors: Hayashi, Kazushi, Hino, Aya, Tao, Hiroaki, Ochi, Mototaka, Goto, Hiroshi, Kugimiya, Toshihiro
Format: Article
Language:English
Subjects:
ANNEALING
Applied physics
ATOMS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
DEPOSITION
DESORPTION
ELECTRON EMISSION
Emission analysis
EMISSION SPECTROSCOPY
EV RANGE 01-10
Evolution
High vacuum
HYDROGEN
Hydrogen atoms
Hydrogen storage
HYDROGENATION
Indium gallium zinc oxide
SPECTRA
SPECTROMETERS
Spectrum analysis
THIN FILMS
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Summary:Total photoyield emission spectroscopy (TPYS) was applied to study the evolution of sub-gap states in hydrogen-treated amorphous In-Ga-Zn-O (a-IGZO) thin films. The a-IGZO thin films were subjected to hydrogen radicals and subsequently annealed in ultra-high vacuum (UHV) conditions. A clear onset of the electron emission was observed at around 4.3 eV from the hydrogen-treated a-IGZO thin films. After successive UHV annealing at 300 °C, the onset in the TPYS spectra was shifted to 4.15 eV, and the photoelectron emission from the sub-gap states was decreased as the annealing temperature was increased. In conjunction with the results of thermal desorption spectrometer, it was deduced that the hydrogen atoms incorporated in the a-IGZO thin films induced metastable sub-gap states at around 4.3 eV from vacuum level just after the hydrogenation. It was also suggested that the defect configuration was changed due to the higher temperature UHV annealing, and that the hydrogen atoms desorbed with the involvement of Zn atoms. These experiments produced direct evidence to show the formation of sub-gap states as a result of hydrogen incorporation into the a-IGZO thin films.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4931143