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Thickness‐Dependent Strain Evolution of Epitaxial SrTiO 3 Thin Films Grown by Ion Beam Sputter Deposition
Author(s) -
Panomsuwan Gasidit,
Saito Nagahiro
Publication year - 2018
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.201700211
Subject(s) - materials science , thin film , epitaxy , vicinal , substrate (aquarium) , tetragonal crystal system , strain (injury) , deposition (geology) , sputter deposition , relaxation (psychology) , composite material , sputtering , crystallography , nanotechnology , layer (electronics) , crystal structure , chemistry , oceanography , biology , psychology , paleontology , social psychology , medicine , organic chemistry , sediment , geology
Epitaxial SrTiO 3 (STO) thin films are grown on vicinal (001)‐oriented LaAlO 3 (LAO) substrates with various thicknesses (3–108 nm) by an ion beam sputter deposition (IBSD). Thickness‐dependent strain in the STO films is investigated comprehensively through the X‐ray analysis. The STO films grow on the LAO substrates under a compressive strain along in‐plane direction ( a ‐ and b ‐axes) and a tensile strain along the growth direction ( c ‐axis). With increasing film thickness, the STO unit cells evolve from more to less tetragonal structure, indicating the occurrence of strain relaxation. Quantitative strain analysis is also carried out for all STO films in terms of biaxial and hydrostatic components. It is found that the major cause of strain in STO films is caused by biaxial component over hydrostatic component. The surface morphology of STO films exhibit a step‐and‐terrace structure with roughness close to the LAO substrate (approx. 0.1 nm), indicating a 2D growth mode. However, as the film thickness increases, the surface terrace become rougher, which is caused by the effect of strain relaxation.