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Title: Growth of highly strained CeO 2 ultrathin films

Abstract

Large biaxial strain is a promising route to tune the functionalities of oxide thin films. However, large strain is often not fully realized due to the formation of misfit dislocations at the film/substrate interface. In this work, we examine the growth of strained ceria (CeO 2) thin films on (001)-oriented single crystal yttria-stabilized zirconia (YSZ) via pulsed-laser deposition. By varying the film thickness systematically between 1 and 430 nm, we demonstrate that ultrathin ceria films are coherently strained to the YSZ substrate for thicknesses up to 2.7 nm, despite the large lattice mismatch (~5%). The coherency is confirmed by both X-ray diffraction and high-resolution transmission electron microscopy. This thickness is several times greater than the predicted equilibrium critical thickness. Partial strain relaxation is achieved by forming semirelaxed surface islands rather than by directly nucleating dislocations. In situ reflective high-energy electron diffraction during growth confirms the transition from 2-D (layer-by-layer) to 3-D (island) at a film thickness of ~1 nm, which is further supported by atomic force microscopy. We propose that dislocations likely nucleate near the surface islands and glide to the film/substrate interface, as evidenced by the presence of 60° dislocations. Finally, an improved understanding of growing oxide thin filmsmore » with a large misfit lays the foundation to systematically explore the impact of strain and dislocations on properties such as ionic transport and redox chemistry.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [3];  [2];  [1]
  1. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Stanford Univ., Stanford, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1348852
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 11; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ceria; dislocation; strain; yttria-stabilized zirconia

Citation Formats

Shi, Yezhou, Lee, Sang Chul, Monti, Matteo, Wang, Colvin, Feng, Zhuoluo A., Nix, William D., Toney, Michael F., Sinclair, Robert, and Chueh, William C. Growth of highly strained CeO2 ultrathin films. United States: N. p., 2016. Web. doi:10.1021/acsnano.6b04081.
Shi, Yezhou, Lee, Sang Chul, Monti, Matteo, Wang, Colvin, Feng, Zhuoluo A., Nix, William D., Toney, Michael F., Sinclair, Robert, & Chueh, William C. Growth of highly strained CeO2 ultrathin films. United States. doi:10.1021/acsnano.6b04081.
Shi, Yezhou, Lee, Sang Chul, Monti, Matteo, Wang, Colvin, Feng, Zhuoluo A., Nix, William D., Toney, Michael F., Sinclair, Robert, and Chueh, William C. Mon . "Growth of highly strained CeO2 ultrathin films". United States. doi:10.1021/acsnano.6b04081. https://www.osti.gov/servlets/purl/1348852.
@article{osti_1348852,
title = {Growth of highly strained CeO2 ultrathin films},
author = {Shi, Yezhou and Lee, Sang Chul and Monti, Matteo and Wang, Colvin and Feng, Zhuoluo A. and Nix, William D. and Toney, Michael F. and Sinclair, Robert and Chueh, William C.},
abstractNote = {Large biaxial strain is a promising route to tune the functionalities of oxide thin films. However, large strain is often not fully realized due to the formation of misfit dislocations at the film/substrate interface. In this work, we examine the growth of strained ceria (CeO2) thin films on (001)-oriented single crystal yttria-stabilized zirconia (YSZ) via pulsed-laser deposition. By varying the film thickness systematically between 1 and 430 nm, we demonstrate that ultrathin ceria films are coherently strained to the YSZ substrate for thicknesses up to 2.7 nm, despite the large lattice mismatch (~5%). The coherency is confirmed by both X-ray diffraction and high-resolution transmission electron microscopy. This thickness is several times greater than the predicted equilibrium critical thickness. Partial strain relaxation is achieved by forming semirelaxed surface islands rather than by directly nucleating dislocations. In situ reflective high-energy electron diffraction during growth confirms the transition from 2-D (layer-by-layer) to 3-D (island) at a film thickness of ~1 nm, which is further supported by atomic force microscopy. We propose that dislocations likely nucleate near the surface islands and glide to the film/substrate interface, as evidenced by the presence of 60° dislocations. Finally, an improved understanding of growing oxide thin films with a large misfit lays the foundation to systematically explore the impact of strain and dislocations on properties such as ionic transport and redox chemistry.},
doi = {10.1021/acsnano.6b04081},
journal = {ACS Nano},
issn = {1936-0851},
number = 11,
volume = 10,
place = {United States},
year = {2016},
month = {11}
}

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