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Title: Evidence That the Anomalous Emission from CaF 2 :Yb 2+ Is Not Described by the Impurity Trapped Exciton Model

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2]; ORCiD logo [2];  [3];  [3]; ORCiD logo [4]
  1. Physics Department, University of California, Santa Cruz, California 95064, United States
  2. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
  3. Dodd-Walls Centre for Photonic and Quantum Technologies and Department of Physics and Astronomy, University of Canterbury, PB 4800, Christchurch 8140, New Zealand
  4. Departamento de Química, Instituto Universitario de Ciencia de Materiales Nicolás Cabrera, and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1390297
DOE Contract Number:
AC02-76SF00515; MAT2011-24586; MAT2014-54395-P
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry Letters; Journal Volume: 8; Journal Issue: 14
Country of Publication:
United States
Language:
English

Citation Formats

MacKeen, C., Bridges, F., Kozina, M., Mehta, A., Reid, M. F., Wells, J. -P. R., and Barandiarán, Z.. Evidence That the Anomalous Emission from CaF 2 :Yb 2+ Is Not Described by the Impurity Trapped Exciton Model. United States: N. p., 2017. Web. doi:10.1021/acs.jpclett.7b01103.
MacKeen, C., Bridges, F., Kozina, M., Mehta, A., Reid, M. F., Wells, J. -P. R., & Barandiarán, Z.. Evidence That the Anomalous Emission from CaF 2 :Yb 2+ Is Not Described by the Impurity Trapped Exciton Model. United States. doi:10.1021/acs.jpclett.7b01103.
MacKeen, C., Bridges, F., Kozina, M., Mehta, A., Reid, M. F., Wells, J. -P. R., and Barandiarán, Z.. Fri . "Evidence That the Anomalous Emission from CaF 2 :Yb 2+ Is Not Described by the Impurity Trapped Exciton Model". United States. doi:10.1021/acs.jpclett.7b01103.
@article{osti_1390297,
title = {Evidence That the Anomalous Emission from CaF 2 :Yb 2+ Is Not Described by the Impurity Trapped Exciton Model},
author = {MacKeen, C. and Bridges, F. and Kozina, M. and Mehta, A. and Reid, M. F. and Wells, J. -P. R. and Barandiarán, Z.},
abstractNote = {},
doi = {10.1021/acs.jpclett.7b01103},
journal = {Journal of Physical Chemistry Letters},
number = 14,
volume = 8,
place = {United States},
year = {Fri Jul 07 00:00:00 EDT 2017},
month = {Fri Jul 07 00:00:00 EDT 2017}
}
  • Materials that luminesce after excitation with ionizing radiation are extensively applied in physics, medicine, security, and industry. Lanthanide dopants are known to trigger crystal scintillation through their fast d–f emissions; the same is true for other important applications as lasers or phosphors for lighting. However, this ability can be seriously compromised by unwanted anomalous emissions often found with the most common lanthanide activators. We report high-resolution X-ray-excited optical (IR to UV) luminescence spectra of CaF2:Yb and SrF2:Yb samples excited at 8949 eV and 80 K. Ionizing radiation excites the known anomalous emission of ytterbium in the CaF2 host but notmore » in the SrF2 host. Wave function-based ab initio calculations of host-to-dopant electron transfer and Yb2+/Yb3+ intervalence charge transfer explain the difference. The model also explains the lack of anomalous emission in Yb-doped SrF2 excited by VUV radiation.« less
  • We show that near-surface defects produced by mechanical treatments and electron irradiation can significantly enhance the intensity of luminescence due to the decay of self-trapped excitons (STEs) in single-crystal calcium fluoride during 157- and 193-nm irradiation. For example, polishing can double the intensity of the STE luminescence. Defects produced by mechanical indentation can either increase or decrease the luminescence intensity, depending on the indentation force. Electron irradiation also enhances subsequent STE luminescence. When electron-irradiated samples are annealed, additional increases in luminescence intensity are observed. Plausible mechanisms for the observed effects on STE luminescence intensity are discussed.
  • We investigated the optical absorption of the fundamental band edge and the origin of the emission from {beta}-FeSi{sub 2} nanoparticles synthesized by ion-beam-induced epitaxial crystallization of Fe{sup +} implanted SiO{sub 2}/Si(100) followed by thermal annealing. From micro-Raman scattering and transmission electron microscopy measurements it was possible to attest the formation of strained {beta}-FeSi{sub 2} nanoparticles and its structural quality. The optical absorption near the fundamental gap edge of {beta}-FeSi{sub 2} nanoparticles evaluated by spectroscopic ellipsometry showed a step structure characteristic of an indirect fundamental gap material. Photoluminescence spectroscopy measurements at each synthesis stage revealed complex emissions in the 0.7-0.9 eVmore » spectral region, with different intensities and morphologies strongly dependent on thermal treatment temperature. Spectral deconvolution into four transition lines at 0.795, 0.809, 0.851, and 0.873 eV was performed. We concluded that the emission at 0.795 eV may be related to a radiative direct transition from the direct conduction band to an acceptor level and that the emission at 0.809 eV derives from a recombination of an indirect bound exciton to this acceptor level of {beta}-FeSi{sub 2}. Emissions 0.851 and 0.873 eV were confirmed to be typical dislocation-related photoluminescence centers in Si. From the energy balance we determined the fundamental indirect and direct band gap energies to be 0.856 and 0.867 eV, respectively. An illustrative energy band diagram derived from a proposed model to explain the possible transition processes involved is presented.« less
  • SnO{sub 2} quantum dots (QDs) are potential materials for deep ultraviolet (DUV) light emitting devices. In this study, we report the temperature and excitation power-dependent exciton luminescence from SnO{sub 2} QDs. The exciton emission exhibits anomalous blue shift, accompanied with band width reduction with increasing temperature and excitation power above 300 K. The anomalous temperature dependences of the peak energy and band width are well interpreted by the strongly localized carrier thermal hopping process and Gaussian shape of band tails states, respectively. The localized wells and band tails at conduction minimum are considered to be induced by the surface oxygen defectsmore » and local potential fluctuation in SnO{sub 2} QDs.« less
  • The first lanthanide(II) cationic species with coordination numbers 7,8, and 9 have been structurally characterized. Mercury amalgams of the elemental lanthanides (Ln(Hg) where Ln = Sm, Eu, Yb) cleanly reduce Mn[sub 2](CO)[sub 10] and Co[sub 2](CO)[sub 8] in polydentate ethers to [Mn(CO)[sub 5]][sup [minus]] and [Co(CO)[sub 4]][sup [minus]] and are oxidized to solvated Ln(II) cations. In the bidentate ether DME (DME = 1,2-dimethoxyethane), [(DME)[sub x]Sm][sup 2+] ions show some association with the metal carbonylate ions, based upon IR evidence. In the tridentate ether DIME (diethylene glycol dimethyl ether = DIME), IR data suggest that only the solvent-separated species [(DIME)[sub 3]Ln][Co(CO)[submore » 4]][sub 2] (Ln: Sm = 3; Yb = 4) and [(DIME)[sub 3]Ln][Mn(CO)[sub 5]][sub 2] (Ln: Sm = 5; Yb = 6; Eu = 7) are formed. Structural characterizations confirm the presence of discrete [(DIME)[sub 3]Sm][sup 2+] and [(DIME)[sub 3]Yb][sup 2+] ions in 3 and 4, in which the DIME oxygens form a 9-coordinate tricapped trigonal prismatic geometry about Ln(II).« less