skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1416194
Grant/Contract Number:
SC0004954
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Ultramicroscopy
Additional Journal Information:
Journal Volume: 178; Journal Issue: C; Related Information: CHORUS Timestamp: 2018-01-09 02:42:49; Journal ID: ISSN 0304-3991
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Liu, Qianlang, March, Katia, and Crozier, Peter A. Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy. Netherlands: N. p., 2017. Web. doi:10.1016/j.ultramic.2016.06.010.
Liu, Qianlang, March, Katia, & Crozier, Peter A. Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy. Netherlands. doi:10.1016/j.ultramic.2016.06.010.
Liu, Qianlang, March, Katia, and Crozier, Peter A. Sat . "Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy". Netherlands. doi:10.1016/j.ultramic.2016.06.010.
@article{osti_1416194,
title = {Nanoscale probing of bandgap states on oxide particles using electron energy-loss spectroscopy},
author = {Liu, Qianlang and March, Katia and Crozier, Peter A.},
abstractNote = {},
doi = {10.1016/j.ultramic.2016.06.010},
journal = {Ultramicroscopy},
number = C,
volume = 178,
place = {Netherlands},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.ultramic.2016.06.010

Citation Metrics:
Cited by: 3works
Citation information provided by
Web of Science

Save / Share:
  • Nanoscale optical band gap variations in epitaxial thin films of two different spinel ferrites, i.e., NiFe₂O₄ (NFO) and CoFe₂O₄ (CFO), have been investigated by spatially resolved high resolution electron energy loss spectroscopy. Experimentally, both NFO and CFO show indirect/direct band gaps around 1.52 eV/2.74 and 2.3 eV, and 1.3 eV/2.31 eV, respectively, for the ideal inverse spinel configuration with considerable standard deviation in the band gap values for CFO due to various levels of deviation from the ideal inverse spinel structure. Direct probing of the regions in both the systems with tetrahedral A site cation vacancy, which is distinct frommore » the ideal inverse spinel configuration, shows significantly smaller band gap values. The experimental results are supported by the density functional theory based modified Becke-Johnson exchange correlation potential calculated band gap values for the different cation configurations.« less
  • 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 primarymore » 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.« less
  • Spin-polarized electron energy-loss spectroscopy has been used to investigate the probing depth of low energy ({similar to}30 eV) electrons at metal surfaces and to study the growth and morphology of monolayer-level metal films. Studies of the Cu(100)/Mo system show that the probing depth in molybdenum is small, {similar to}1 monolayer, and that molybdenum grows layer-by-layer on Cu(100). Data for the Cu(100)/Fe system are also reported that suggest that iron deposition on a room-temperature Cu(100) substrate does not initially result in simple layer-by-layer growth.
  • Layer specific direct measurement of optical band gaps of two important van der Waals compounds, MoS{sub 2} and ReS{sub 2}, is performed at nanoscale by high resolution electron energy loss spectroscopy. For monolayer MoS{sub 2}, the twin excitons (1.8 and 1.95 eV) originating at the K point of the Brillouin zone are observed. An indirect band gap of 1.27 eV is obtained from the multilayer regions. Indirect to direct band gap crossover is observed which is consistent with the previously reported strong photoluminescence from the monolayer MoS{sub 2}. For ReS{sub 2}, the band gap is direct, and a value of 1.52 andmore » 1.42 eV is obtained for the monolayer and multilayer, respectively. The energy loss function is dominated by features due to high density of states at both the valence and conduction band edges, and the difference in analyzing band gap with respect to ZnO is highlighted. Crystalline 1T ReS{sub 2} forms two dimensional chains like superstructure due to the clustering between four Re atoms. The results demonstrate the power of HREELS technique as a nanoscale optical absorption spectroscopy tool.« less