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Title: Effect of photon irradiation on conductivity of nanoscale yttria-doped zirconia thin films

Abstract

The effect of photon irradiation on high temperature conductivity of nanoscale yttria-doped zirconia thin films is reported. Nanoscale films show substantial decrease in total conductivity (as high as {approx}40%) during ultraviolet (UV) irradiation, while the conductivity of bulk single crystals shows negligible changes. The UV induced conductivity changes are rapid and reversible and activation energies for ion migration remain unaffected. The reduction in conductivity may arise from changes in effective oxygen vacancy concentration. Such UV-influenced alteration of electrical properties offers an elegant route to tailor surface catalytic activity of oxygen ion and mixed conductors used in various solid-state devices.

Authors:
;  [1]
  1. Harvard School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, Massachusetts 02138 (United States)
Publication Date:
OSTI Identifier:
20971859
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 90; Journal Issue: 9; Other Information: DOI: 10.1063/1.2709990; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACTIVATION ENERGY; CATALYSIS; DOPED MATERIALS; IONIC CONDUCTIVITY; IRRADIATION; MONOCRYSTALS; NANOSTRUCTURES; OXYGEN; OXYGEN IONS; PHOTONS; PHYSICAL RADIATION EFFECTS; THIN FILMS; ULTRAVIOLET RADIATION; VACANCIES; YTTRIUM OXIDES; ZIRCONIUM OXIDES

Citation Formats

Karthikeyan, Annamalai, and Ramanathan, Shriram. Effect of photon irradiation on conductivity of nanoscale yttria-doped zirconia thin films. United States: N. p., 2007. Web. doi:10.1063/1.2709990.
Karthikeyan, Annamalai, & Ramanathan, Shriram. Effect of photon irradiation on conductivity of nanoscale yttria-doped zirconia thin films. United States. doi:10.1063/1.2709990.
Karthikeyan, Annamalai, and Ramanathan, Shriram. Mon . "Effect of photon irradiation on conductivity of nanoscale yttria-doped zirconia thin films". United States. doi:10.1063/1.2709990.
@article{osti_20971859,
title = {Effect of photon irradiation on conductivity of nanoscale yttria-doped zirconia thin films},
author = {Karthikeyan, Annamalai and Ramanathan, Shriram},
abstractNote = {The effect of photon irradiation on high temperature conductivity of nanoscale yttria-doped zirconia thin films is reported. Nanoscale films show substantial decrease in total conductivity (as high as {approx}40%) during ultraviolet (UV) irradiation, while the conductivity of bulk single crystals shows negligible changes. The UV induced conductivity changes are rapid and reversible and activation energies for ion migration remain unaffected. The reduction in conductivity may arise from changes in effective oxygen vacancy concentration. Such UV-influenced alteration of electrical properties offers an elegant route to tailor surface catalytic activity of oxygen ion and mixed conductors used in various solid-state devices.},
doi = {10.1063/1.2709990},
journal = {Applied Physics Letters},
number = 9,
volume = 90,
place = {United States},
year = {Mon Feb 26 00:00:00 EST 2007},
month = {Mon Feb 26 00:00:00 EST 2007}
}
  • Structural changes and atomic-scale interfacial phenomena induced by room temperature ultraviolet (UV) irradiation on yttria-doped zirconia (YDZ) thin films grown on semiconductor substrates have been investigated in detail. Interfacial layer formation, film densification, and changes in crystallinity were observed in films grown on Si, while there was minimal difference in films grown on Ge. No significant grain growth and phase transformation were observed, suggesting that cation related kinetics remains unperturbed under UV exposure. The formation of interfacial layers thicker than room temperature self-limiting thickness suggests that effective local field for oxygen vacancies inside the YDZ film was affected by photonmore » illumination.« less
  • We report on synthesis, structural evolution, and high temperature properties of ultrathin yttria-doped-zirconia (YDZ) films grown by alloy oxidation under ultraviolet (UV) irradiation. From high-resolution studies on interfacial layer growth kinetics, we found that oxygen diffusivity maximum in UV-YDZ film is located at higher yttria concentration than that in thermally oxidized films. It is likely that the oxygen-rich nature of UV-grown films enabled by photon irradiation is responsible for the observed differences. The results demonstrate routes for synthesis of oxide films with controlled structure and stoichiometry.
  • Taking advantage of the fact that TiO{sub 2} additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on both solutions were prepared by solid state reaction. In particular, additions of 15 mol% of TiO{sub 2} give rise to composite materials constituted by 0.51 mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49 mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y{sub 2}(Ti{sub 1-y}Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as an impurity phase with y close to 1, according to FT-Raman results. Lower and highermore » additions of titania than that of 15 mol%, i.e., x=0, 5, 10, 20, 25 and 30 mol% were considered to study the evolution of 8YSZ phase as a function of the TiO{sub 2} content. Furthermore, zirconium titanate phase (ZrTiO{sub 4}) is detected when the titania content is equal or higher than 20 mol% and this phase admits Y{sub 2}O{sub 3} in solid solution according to FE-SEM-EDX. The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the pO{sub 2} range from 0.21 to 10{sup -7.5} atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01 S/cm. The ionic plus electronic conductivity is 0.02 S/cm at 1000 {sup o}C and 10{sup -12.3} atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a -1/4 pO{sub 2} dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}. -- Graphical abstract: FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material. Display Omitted Research highlights: {yields} Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors under low partial pressures. {yields} From 5 mol% of TiO{sub 2}, Y{sub 2}(Ti{sub 1-y},Zr{sub y}){sub 2}O{sub 7} pyrochlore is present as a minor phase, being y close to 1 according to FT-Raman studies. {yields} The onset of the electronic conductivity under reducing conditions exhibit a -1/4 pO{sub 2} dependence. The n-type electronic conduction is due to a small polaron-hopping between Ti{sup 3+} and Ti{sup 4+}.« less
  • The monolithic integration of thermoelectric generators and magnetoresistive functionality on the basis of misfit cobaltate [Ca{sub 2}CoO{sub 3}]{sub 0.62}[CoO{sub 2}] thin films into silicon technology is a prerequisite for their application in miniaturized electric circuits. Here, we report on [Ca{sub 2}CoO{sub 3}]{sub 0.62}[CoO{sub 2}] thin films grown by pulsed laser deposition on (001)-silicon with a thin epitaxial yttria-stabilized zirconia (YSZ) buffer layer. X-ray diffraction and cross-sectional high resolution transmission electron microscopy analysis reveal that high quality c-axis oriented heteroepitaxial [Ca{sub 2}CoO{sub 3}]{sub 0.62}[CoO{sub 2}] films with a 12-fold in-plane rotational symmetry can be grown, which exhibit remarkable lower electrical resistivitymore » compared to those with random in-plane orientation. This result is explained by energetically preferred epitaxial growth directions of the pseudo hexagonal [CoO{sub 2}] sublayer in monoclinic [Ca{sub 2}CoO{sub 3}]{sub 0.62}[CoO{sub 2}] onto the cubic (001)-YSZ surface leading to a highly symmetric in-plane mutual orientation of the charge transporting CoO{sub 2} sublayer domains.« less
  • Yttria fully stabilized zirconia (FSZ) is a candidate material for nuclear inert matrix fuel cell and nuclear waste containment due to its isostructure with UO{sub 2} and PuO{sub 2} and its outstanding radiation resistance. Amorphous and polycrystalline cubic FSZ thin films of thickness around 400 nm were deposited on (100) Si by ultraviolet pulsed laser ablation and irradiated with 2.6 GeV uranium ions at fluences between 2x10{sup 11} and 1.2x10{sup 12} ions cm{sup -2}. The films were characterized before and after irradiation using scanning electron microscopy, atomic force microscopy, grazing incidence x-ray diffraction, and x-ray photoelectron spectroscopy (XPS). Amorphization, followedmore » by partial recrystallization, is observed for irradiated crystalline films, whereas the amorphous films remain unaltered. A shift in the relative position of the XPS Zr 3d, Y 3d, and O 1s core lines is observed upon irradiation both in the crystalline and amorphous films, indicating differences in the local chemical environment at the surface as well as in near-surface layers. Such changes are ascribed to oxygen migration at the film surface, which may promote the recrystallization of as-deposited crystalline films but does not affect amorphous films.« less