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Title: Formation and Thickness Evolution of Periodic Twin Domains in Manganite Films Grown on SrTiO3(001) Substrates

Abstract

We present an extended synchrotron x-ray scattering study of the structure of thin manganite films grown on SrTiO3(001) substrates and reveal a new kind of misfit strain relaxation process which exploits twinning to adjust lattice mismatch. We show that this relaxation mechanism emerges in thin films as one-dimensional twinning waves which freeze out into a twin domain pattern as the manganite film continues to grow. A quantitative microscopic model which uses a matrix formalism is able to reproduce all x-ray features and provides a detailed insight into this novel relaxation mechanism. We further demonstrate how this twin angle pattern affects the transport properties in these functional films.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959516
Report Number(s):
BNL-82502-2009-JA
Journal ID: ISSN 0031-9007; PRLTAO; TRN: US1005750
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 98
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; FUNCTIONALS; RELAXATION; SCATTERING; STRAINS; STRONTIUM TITANATES; SUBSTRATES; SYNCHROTRONS; THICKNESS; THIN FILMS; TRANSPORT; TWINNING; X-RAY DIFFRACTION; national synchrotron light source

Citation Formats

Gebhardt,U., Kasper, N., Vigliante, A., Wochner, P., Dosch, H., Razavi, F., and Habermeier, H.. Formation and Thickness Evolution of Periodic Twin Domains in Manganite Films Grown on SrTiO3(001) Substrates. United States: N. p., 2007. Web. doi:10.1103/PhysRevLett.98.096101.
Gebhardt,U., Kasper, N., Vigliante, A., Wochner, P., Dosch, H., Razavi, F., & Habermeier, H.. Formation and Thickness Evolution of Periodic Twin Domains in Manganite Films Grown on SrTiO3(001) Substrates. United States. doi:10.1103/PhysRevLett.98.096101.
Gebhardt,U., Kasper, N., Vigliante, A., Wochner, P., Dosch, H., Razavi, F., and Habermeier, H.. Mon . "Formation and Thickness Evolution of Periodic Twin Domains in Manganite Films Grown on SrTiO3(001) Substrates". United States. doi:10.1103/PhysRevLett.98.096101.
@article{osti_959516,
title = {Formation and Thickness Evolution of Periodic Twin Domains in Manganite Films Grown on SrTiO3(001) Substrates},
author = {Gebhardt,U. and Kasper, N. and Vigliante, A. and Wochner, P. and Dosch, H. and Razavi, F. and Habermeier, H.},
abstractNote = {We present an extended synchrotron x-ray scattering study of the structure of thin manganite films grown on SrTiO3(001) substrates and reveal a new kind of misfit strain relaxation process which exploits twinning to adjust lattice mismatch. We show that this relaxation mechanism emerges in thin films as one-dimensional twinning waves which freeze out into a twin domain pattern as the manganite film continues to grow. A quantitative microscopic model which uses a matrix formalism is able to reproduce all x-ray features and provides a detailed insight into this novel relaxation mechanism. We further demonstrate how this twin angle pattern affects the transport properties in these functional films.},
doi = {10.1103/PhysRevLett.98.096101},
journal = {Physical Review Letters},
number = ,
volume = 98,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We present an extended synchrotron x-ray scattering study of the structure of thin manganite films grown on SrTiO{sub 3}(001) substrates and reveal a new kind of misfit strain relaxation process which exploits twinning to adjust lattice mismatch. We show that this relaxation mechanism emerges in thin films as one-dimensional twinning waves which freeze out into a twin domain pattern as the manganite film continues to grow. A quantitative microscopic model which uses a matrix formalism is able to reproduce all x-ray features and provides a detailed insight into this novel relaxation mechanism. We further demonstrate how this twin angle patternmore » affects the transport properties in these functional films.« less
  • The dislocation structure at the initial stage of relaxation of Ge{sub x}Si{sub 1-x} films (x{approx}0.4-0.8) grown on Si(001) substrates tilted at 6 deg. to the nearest (111) plane is studied. One of the directions along which edge dislocations are formed is no longer in the plane of the interface but crosses the latter at the angle of miscut. Therefore, long edge misfit dislocations (MDs) cannot exist in the direction of substrate misorientation, because their ends move away from the interface during dislocation propagation. Two different mechanisms of formation of short segments of edge (90 deg. ) MDs in the directionmore » of substrate misorientation are found. The first mechanism is the correlated nucleation of complementary 60 deg. dislocation half-loops manifested in the form of the so-called Y-center consisting of a short segment of the 90 deg. MD and 60 deg. MDs diverging from this segment in form of two rays in the miscut direction. In the second mechanism, the 90 deg. MD segment is formed owing to intersection of already existing complementary 60 deg. MDs slipping in mirrorlike inclined planes {l_brace}111{r_brace}. Samples annealed at higher temperatures contain MD segments, which lose their contrast on one of the TEM images taken to detect edge dislocation segments in the two-wave diffraction mode but do not coincide with the direction [110] (they pass along the intersections of the mirrorlike inclined planes {l_brace}111{r_brace} with the surface of the misoriented Si substrate). To explain this phenomenon, a model is proposed, where one of the pair of complementary 60 deg. MDs propagating at an angle to each other continuously approaches the other by the cross-slip mechanism. Formation of a chain of edge MD segments connected by a pair of 60 deg. MDs becomes possible. The averaged direction of such a dislocation structure coincides with the direction of one of the 60 deg. MDs.« less
  • We have prepared VO{sub 2} thin films epitaxially grown on TiO{sub 2}(001) substrates with thickness systematically varied from 2.5 to 13 nm using a pulsed laser deposition method, and studied the transport property and electronic states of the films by means of resistivity and in situ synchrotron photoemission spectroscopy (SRPES). In resistivity measurements, the 13-nm-thick film exhibits a metal-insulator transition at around 290 K on cooling with change of three orders of magnitudes in resistivity. As the film thickness decreases, the metal-insulator transition broadens and the transition temperature increases. Below 4 nm, the films do not show the transition andmore » become insulators. In situ SRPES measurements of near the Fermi level valence band find that the electronic state of the 2.5-nm-thick film is different than that of the temperature-induced insulator phase of VO{sub 2} itself although these two states are insulating. Ti 2p core-level photoemission measurements reveal that Ti ions exist near the interface between the films and TiO{sub 2} substrates, with a chemical state similar to that in (V,Ti)O{sub 2} solid solution. These results indicate that insulating (V,Ti)O{sub 2} solid solution is formed in the thinner films. We propose a simple growth model of a VO{sub 2} thin film on a TiO{sub 2}(001) substrate. Near the interface, insulating (V,Ti)O{sub 2} solid solution is formed due to the diffusion of Ti ions from the TiO{sub 2} substrate into the VO{sub 2} film. The concentration of Ti in (V,Ti)O{sub 2} is relatively high near the interface and decreases toward the surface of the film. Beyond a certain film thickness (about 7 nm in the case of the present 13-nm-thick film), the VO{sub 2} thin film without any Ti ions starts to grow. Our work suggests that developing a technique for preparing the sharp interface between the VO{sub 2} thin films and TiO{sub 2} substrates is a key issue to study the physical property of an ultrathin film of ''pure'' VO{sub 2}, especially to examine the presence of the novel electronic state called a semi-Dirac point phase predicted by calculations.« less
  • Ninety degree edge misfit dislocations (MDs) are 'sessile' dislocations; such dislocations, however, were found in large amounts in relaxed films. The commonly accepted formation mechanism of such dislocations is an interaction of two complementary 60 deg. dislocations with appropriate Burger's vectors, for example: a/2[101] + a/2 [011] = a/2 [110]. In the present study, four possible types of interaction were analyzed: (i) random meeting of two complementary MDs; (ii) crossing of two complementary 60 deg. MDs in the vicinity of film-substrate interface in systems grown on substrates misoriented from exact (001) orientation; (iii) formation of edge MDs during cross-slipping ofmore » a secondary MD; and (iv) induced nucleation of a secondary complementary 60 deg. MD. Examples of discussed interactions are given. Contrary to the widespread opinion that edge MDs in GeSi and InGaAs films grown by MBE on Si and GaAs substrates predominantly form under elastic strains greater than 2% and at the final stage of plastic relaxation, in the present study, we show that such dislocations may also form at an early stage of plastic relaxation in films with less-than-1% lattice misfit with substrate. A necessary condition for that is a sufficient amount of 60 deg. dislocations available in the system by the moment the strained film starts growing. Dislocations (60 deg. ) can be introduced into the system using a preliminarily grown, partially or fully relaxed buffer layer. This layer serves as a source of threading dislocations for the next growing layer that favor the formation of paired complementary MDs and their 'reagents', edge MDs, at the interface with growing film.« less
  • No abstract prepared.