New Approach in Equilibrium Theory for Strained Layer Relaxation

Fischer, A.; Kühne, H.; Richter, Hans

doi:10.1103/physrevlett.73.2712

Cited by 211 publications

(136 citation statements)

References 10 publications

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“…Several models have been developed from Matthews-Blakeslee's, for metals and semiconductors. Let us cite the one by Fischer et al [167] who extended Matthews-Blakeslee's model to take into account the interaction between straight dislocations and the one by Chidambarrao et al [168] who also extended it by taking into account the effect of Peierls barrier. However, for ferroelectrics, it usually predicts critical thicknesses that are smaller than what has been observed experimentally.…”

Section: Critical Thickness For Dislocations Generationmentioning

confidence: 99%

Strain on ferroelectric thin films

Janolin

2009

J Mater Sci

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Strain engineering aims to take advantage of the stress field imposed by substrates on thin films. It requires an understanding of the consequences of stress fields on the physical properties of the deposited materials. This is achieved in ferroelectric thin films through the use of misfit-strain phase diagrams that show the stability regions for the possible phases. These encompass bulk phases as well as new ones exhibiting symmetries that are not present in the bulk. For the solid solution lead zirconate-lead titanate, Pb(Zr 1-x Ti x )O 3 , monoclinic phases found in the bulk morphotropic phase boundary region and associated to concentrations exhibiting the highest properties can be stabilized on a wider range of composition in thin films. In addition, phases of lower symmetry can be stabilized through the use of anisotropic biaxial stress fields, generated by orthorhombic substrates for example. Another crucial aspect of the influence of biaxial stress fields is the generation of domain structures. Theoretical tools as well as experimental verifications have provided much insight on the underlying physics. We, therefore, present here an overview of the influence of both iso-and anisotropic biaxial stress fields on the structures and properties of ferroelectric thin films exemplified on Pb(Zr 1-x Ti x )O 3 .

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Section: Critical Thickness For Dislocations Generationmentioning

confidence: 99%

Strain on ferroelectric thin films

Janolin

2009

J Mater Sci

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“…Using the theoretical models of Fischer et al . [26] and Matthews and Blakeslee [27] that have been successful in predicting the conditions, i.e., in GaAsP systems [27] a relaxation of the biaxially compressed layer should occur for critical layer thicknesses of 4 -14 nm (x=0.1) and 6.3 nm (x=0.2) when room temperature stiffness constants of GaN are applied [24]. Here, however, for all the Ga 1-x In x N/GaN samples in the study (0<x<0.2) no relaxation can be observed at a ternary film thickness of 40 nm.…”

Section: Strain and Compositionmentioning

confidence: 99%

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

Wetzel

Nitta

Takeuchi

et al. 1998

MRS Internet j. nitride semicond. res.

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A study of the optoelectronic properties of strained 40 nm Ga 1-x In x N layers on GaN films is presented. The fact of pseudomorphic strain leads to a new interpretation of the film composition when derived from x-ray scattering. In addition we directly confirm that strain induces huge piezoelectric fields in this uniaxial system by the observation of Franz-Keldysh oscillations in photoreflection. As a function of composition (0 < x < 0.2) and strain we derive the electronic band gap energy and the piezoelectric field strength. We interpret both in terms of effective bowing parameters and piezoelectric coefficients, respectively. From a spatially resolved micro photoluminescence at room temperature we find no evidence for spatial band gap or composition variations of more than 60 meV over the length scale from 1 to 50 µ m (x=0.187) in our material. At the same time, an observed discrepancy between photoluminescence peak energy and photoreflection band gap energy increases with x to some 160 meV. We attribute this redshift to photon assisted tunneling in the huge piezoelectric fields (Franz-Keldysh effect).

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“…For example, sample B is partially relaxed while a thinner one ͑A͒ is almost fully relaxed, and a thicker one ͑G͒ is pseudomorphic. Critical thicknesses can, for some samples, be well above the values calculated using the relaxation models, 27,28 as pointed out in Ref. 22.…”

mentioning

confidence: 99%

Compositional dependence of the strain-free optical band gap in InxGa1−xN layers

Pereira

Correia

Monteiro

et al. 2001

Applied Physics Letters

112

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The effect of strain on the compositional and optical properties of a set of epitaxial single layers of In x Ga 1Ϫx N was studied. Indium content was measured free from the effects of strain by Rutherford backscattering spectrometry. Accurate knowledge of the In mole fraction, combined with x-ray diffraction measurements, allows perpendicular strain (⑀ zz ) to be evaluated. Optical band gaps were determined by absorption spectroscopy and corrected for strain. Following this approach, the strain free dependence of the optical band gap in In x Ga 1Ϫx N alloys was determined for xр0.25. Our results indicate an ''anomalous,'' linear, dependence of the energy gap on the In content, at room temperature: E g (x)ϭ3.39-3.57x eV. Extension of this behavior to higher concentrations is discussed on the basis of reported results.

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New Approach in Equilibrium Theory for Strained Layer Relaxation

Cited by 211 publications

References 10 publications

Strain on ferroelectric thin films

Strain on ferroelectric thin films

On the Bandstructure in GaInN/GaN Heterostructures - Strain, Band Gap and Piezoelectric Effect

Compositional dependence of the strain-free optical band gap in InxGa1−xN layers

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