Anisotropic strain relaxation in (Ba{sub 0.6}Sr{sub 0.4})TiO{sub 3} epitaxial thin films
- Department of Ceramic and Materials Engineering, Rutgers, State University of New Jersey, Piscataway, New Jersey 08854 (United States)
We have studied the evolution of anisotropic epitaxial strains in <110>-oriented (Ba{sub 0.60}Sr{sub 0.40})TiO{sub 3} paraelectric (m3m) thin films grown on orthorhombic (mm2) <100>-oriented NdGaO{sub 3} by high-resolution x-ray diffractometry. All the six independent components of the three-dimensional strain tensor were measured in films with 25-1200-nm thickness, from which the principal stresses and strains were obtained. Pole figure analysis indicated that the epitaxial relations are [001]{sub m3m} parallel [001]{sub mm2} and [110]{sub m3m} parallel [010]{sub mm2} in the plane of the film, and [110]{sub m3m} parallel [100]{sub mm2} along the growth direction. The dislocation system responsible for strain relief along [001] has been determined to be vertical bar b vertical bar{sup (001)}=3/4 vertical bar b vertical bar. Strain relief along the [110] direction, on the other hand, has been determined to be due to a coupled mechanism given by vertical bar b vertical bar{sup (110)}=vertical bar b vertical bar and vertical bar b vertical bar{sup (110)}={radical}(3)/4vertical bar b vertical bar. Critical thicknesses, as determined from nonlinear regression using the Matthews-Blakeslee equation, for misfit dislocation formation along [001] and [110] direction were found to be 5 and 7 nm, respectively. The residual strain energy density was calculated as {approx}2.9x10{sup 6} J/m{sup 3} at 25 nm, which was found to relax an order of magnitude by 200 nm. At 200 nm, the linear dislocation density along [001] and [110] are {approx}6.5x10{sup 5} and {approx}6x10{sup 5} cm{sup -1}, respectively. For films thicker than 600 nm, additional strain relief occurred through surface undulations, indicating that this secondary strain-relief mechanism is a volume effect that sets in upon cooling from the growth temperature.
- OSTI ID:
- 20709649
- Journal Information:
- Journal of Applied Physics, Vol. 97, Issue 10; Other Information: DOI: 10.1063/1.1901833; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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