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Title: Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers

Abstract

We demonstrate the strain release of LaAlO{sub 3} epitaxial film on SrTiO{sub 3} (001) by inserting ultra-thin 'SrAlO{sub x}' buffer layers. Although SrAlO{sub x} is not a perovskite, nor stable as a single phase in bulk, epitaxy stabilizes the perovskite structure up to a thickness of 2 unit cells (uc). At a critical thickness of 3 uc of SrAlO{sub x}, the interlayer acts as a sliding buffer layer, and abruptly relieves the lattice mismatch between the LaAlO{sub 3} filmand the SrTiO{sub 3} substrate, while maintaining crystallinity. This technique may provide a general approach for strain relaxation of perovskite film far below the thermodynamic critical thickness. A central issue in heteroepitaxial filmgrowth is the inevitable difference in lattice constants between the filmand substrate. Due to this lattice mismatch, thin film are subjected to microstructural strain, which can have a significan effect on the filmproperties. This challenge is especially prominent in the rapidly developing fiel of oxide electronics, where much interest is focused on incorporating the emergent physical properties of oxides in devices. Although strain can be used to great effect to engineer unusual ground states, it is often deleterious for bulk first-orde phase transitions, which are suppressed by the strain andmore » symmetry constraints of the substrate. While there are some reports discussing the control of the lattice mismatch in oxides using thick buffer layers, the materials choice, lattice-tunable range, and control of misfit dislocations are still limited. In this Letter, we report the fabrication of strain-relaxed LaAlO{sub 3} (LAO) thin film on SrTiO{sub 3} (STO) (001) using very thin 'SrAlO{sub x}' (SAO) buffer layers. Whereas for 1 or 2 pseudo-perovskite unit cells (uc) of SAO, the subsequent LAO filmis strained to the substrate, at a critical thickness of 3 uc the SAO interlayer abruptly relieves the lattice mismatch between the LAO and the STO, although maintaining the relative crystalline orientation between the filmand the substrate. For 4 uc or greater, the perovskite epitaxial template is lost and the LAO filmis amorphous. These results suggest that metastable interlayers can be used for strain release on the nanometer scale.« less

Authors:
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1024167
Report Number(s):
SLAC-PUB-14516
Journal ID: ISSN 0003-6951; APPLAB; TRN: US201119%%103
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Journal Article
Journal Name:
Applied Physics Letters 98, 171901:1-3 (2011)
Additional Journal Information:
Journal Volume: 98; Journal Issue: 17; Journal ID: ISSN 0003-6951
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BUFFERS; DISLOCATIONS; ENGINEERS; EPITAXY; FABRICATION; GROUND STATES; ORIENTATION; OXIDES; PEROVSKITE; PHYSICAL PROPERTIES; RELAXATION; STRAINS; SYMMETRY; THERMODYNAMICS; THICKNESS; THIN FILMS; PHYS

Citation Formats

Bell, Christopher. Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers. United States: N. p., 2011. Web.
Bell, Christopher. Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers. United States.
Bell, Christopher. Thu . "Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers". United States. https://www.osti.gov/servlets/purl/1024167.
@article{osti_1024167,
title = {Nanometer-Scale Epitaxial Strain Release in Perovskite Heterostructures Using 'SrAlOx' Sliding Buffer Layers},
author = {Bell, Christopher},
abstractNote = {We demonstrate the strain release of LaAlO{sub 3} epitaxial film on SrTiO{sub 3} (001) by inserting ultra-thin 'SrAlO{sub x}' buffer layers. Although SrAlO{sub x} is not a perovskite, nor stable as a single phase in bulk, epitaxy stabilizes the perovskite structure up to a thickness of 2 unit cells (uc). At a critical thickness of 3 uc of SrAlO{sub x}, the interlayer acts as a sliding buffer layer, and abruptly relieves the lattice mismatch between the LaAlO{sub 3} filmand the SrTiO{sub 3} substrate, while maintaining crystallinity. This technique may provide a general approach for strain relaxation of perovskite film far below the thermodynamic critical thickness. A central issue in heteroepitaxial filmgrowth is the inevitable difference in lattice constants between the filmand substrate. Due to this lattice mismatch, thin film are subjected to microstructural strain, which can have a significan effect on the filmproperties. This challenge is especially prominent in the rapidly developing fiel of oxide electronics, where much interest is focused on incorporating the emergent physical properties of oxides in devices. Although strain can be used to great effect to engineer unusual ground states, it is often deleterious for bulk first-orde phase transitions, which are suppressed by the strain and symmetry constraints of the substrate. While there are some reports discussing the control of the lattice mismatch in oxides using thick buffer layers, the materials choice, lattice-tunable range, and control of misfit dislocations are still limited. In this Letter, we report the fabrication of strain-relaxed LaAlO{sub 3} (LAO) thin film on SrTiO{sub 3} (STO) (001) using very thin 'SrAlO{sub x}' (SAO) buffer layers. Whereas for 1 or 2 pseudo-perovskite unit cells (uc) of SAO, the subsequent LAO filmis strained to the substrate, at a critical thickness of 3 uc the SAO interlayer abruptly relieves the lattice mismatch between the LAO and the STO, although maintaining the relative crystalline orientation between the filmand the substrate. For 4 uc or greater, the perovskite epitaxial template is lost and the LAO filmis amorphous. These results suggest that metastable interlayers can be used for strain release on the nanometer scale.},
doi = {},
journal = {Applied Physics Letters 98, 171901:1-3 (2011)},
issn = {0003-6951},
number = 17,
volume = 98,
place = {United States},
year = {2011},
month = {8}
}