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Title: Band gap and defect states of MgO thin films investigated using reflection electron energy loss spectroscopy

The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS) and high-energy resolution REELS (HR-REELS). HR-REELS with a primary electron energy of 0.3 keV revealed that the surface F center (FS) energy was located at approximately 4.2 eV above the valence band maximum (VBM) and the surface band gap width (E{sub g}{sup S}) was approximately 6.3 eV. The bulk F center (F{sub B}) energy was located approximately 4.9 eV above the VBM and the bulk band gap width was about 7.8 eV, when measured by REELS with 3 keV primary electrons. From a first-principles calculation, we confirmed that the 4.2 eV and 4.9 eV peaks were F{sub S} and F{sub B}, induced by oxygen vacancies. We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies. Finally, we calculated the secondary electron emission yields (γ) for various noble gases. He and Ne were not influenced by the defect states owing to their higher ionization energies, but Ar, Kr, and Xe exhibited a stronger dependence on the defect states owing to their small ionization energies.
Authors:
 [1] ;  [2] ;  [3] ; ;  [1] ;  [4] ;  [5] ; ;  [6]
  1. Analytical Engineering Group, Samsung Advanced Institute of Technology, 130, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, S. Korea, 443-803 (Korea, Republic of)
  2. (Korea, Republic of)
  3. CAE Group, Samsung Advanced Institute of Technology, 130, Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, S. Korea, 443-803 (Korea, Republic of)
  4. Department of Physics, Chungbuk National University, Cheongju, S. Korea (Korea, Republic of)
  5. Analysis & Simulation Center, Asahi Kasei Corporation, 2-1 Samejima, Fuji, Shizuoka 416-8501 (Japan)
  6. College of Information and Communication Engineering, Sungkyunkwan University, Cheoncheon-dong 300, Jangan-gu, Suwon 440-746, S. Korea (Korea, Republic of)
Publication Date:
OSTI Identifier:
22492270
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 5; Journal Issue: 7; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ELECTRON EMISSION; ELECTRONIC STRUCTURE; ELECTRONS; ENERGY GAP; ENERGY LEVELS; ENERGY RESOLUTION; ENERGY-LOSS SPECTROSCOPY; EV RANGE; F CENTERS; HELIUM; IONIZATION; KEV RANGE; MAGNESIUM OXIDES; NEON; OXYGEN; REFLECTION; SURFACES; THIN FILMS; VALENCE