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Young T.D., Jurczak G., Lotsari A.♦, Dimitrakopulos G.P.♦, Komninou Ph.♦, Dłużewski P., A study of the piezoelectric properties of semipolar 11(2)over-bar2 GaN/AlN quantum dots,
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, ISSN: 0370-1972, DOI: 10.1002/pssb.201552156, Vol.252, No.10, pp.2296-2303, 2015Streszczenie: GaN quantum dots grown in (inline image)’orientated AlN are studied. The inline image-nucleated quantum dots exhibit rectangular- or trapezoid-based truncated pyramidal morphology. Another quantum dot type orientated on inline image is reported. Based on high-resolution transmission microscopy and crystal symmetry, the geometry of inline image-orientated quantum dots is proposed. A piezoelectric model is used within a finite element method to determine and compare the strain-state and electrostatic potential associated with the quantum dot morphology and an estimation of the band-edge energy is made. We report on some novel properties of the inline image-orientated quantum dot, including mixed strain-states and strain-state bowing. Słowa kluczowe: III–V semiconductors, AlN, GaN, nanostructures, piezoelectric properties, quantum dots Afiliacje autorów:
Young T.D. | - | IPPT PAN | Jurczak G. | - | IPPT PAN | Lotsari A. | - | Aristotle University of Thessaloniki (GR) | Dimitrakopulos G.P. | - | Aristotle University of Thessaloniki (GR) | Komninou Ph. | - | Aristotle University of Thessaloniki (GR) | Dłużewski P. | - | IPPT PAN |
| | 20p. |
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Dimitrakopulos G.P.♦, Kalesaki E.♦, Kioseoglou J.♦, Kehagias T.♦, Lotsari A.♦, Lahourcade L.♦, Monroy E.♦, Häusler I.♦, Kirmse H.♦, Neumann W.♦, Jurczak G., Young T.D., Dłużewski P., Komninou Ph.♦, Karakostas T.♦, Morphology and strain of self-assembled semi-polar GaN quantum dots in (1112) AlN,
JOURNAL OF APPLIED PHYSICS, ISSN: 0021-8979, DOI: 10.1063/1.3506686, Vol.108, pp.104304-1-9, 2010Streszczenie: GaN quantum dots (QDs) grown in semipolar (11-22) AlN by plasma-assisted molecular-beam epitaxy were studied by transmission electron microscopy (TEM) and scanning transmission electron microscopy techniques. The embedded (11-2)-grown QDs exhibited pyramidal or truncated-pyramidal morphology consistent with the symmetry of the nucleating plane, and were delimited by nonpolar and semipolar nanofacets. It was also found that, in addition to the (11-22) surface, QDs nucleated at depressions comprising {10-11} facets. This was justified by ab initio density functional theory calculations showing that such GaN/AlN facets are of lower energy compared to (11-22). Based on quantitative high-resolution TEM strain measurements, the three-dimensional QD strain state was analyzed using finite-element simulations. The internal electrostatic field was then estimated, showing small potential drop along the growth direction, and limited localization at most QD interfaces. Słowa kluczowe: Quantum dots, Transmission electron microscopy, III-V semiconductors, High resolution transmission electron microscopy, Epitaxy Afiliacje autorów:
Dimitrakopulos G.P. | - | Aristotle University of Thessaloniki (GR) | Kalesaki E. | - | Aristotle University of Thessaloniki (GR) | Kioseoglou J. | - | Aristotle University of Thessaloniki (GR) | Kehagias T. | - | Aristotle University of Thessaloniki (GR) | Lotsari A. | - | Aristotle University of Thessaloniki (GR) | Lahourcade L. | - | CNRS (FR) | Monroy E. | - | CNRS (FR) | Häusler I. | - | Humboldt-Universität zu Berlin (DE) | Kirmse H. | - | Humboldt-Universität zu Berlin (DE) | Neumann W. | - | Humboldt-Universität zu Berlin (DE) | Jurczak G. | - | IPPT PAN | Young T.D. | - | IPPT PAN | Dłużewski P. | - | IPPT PAN | Komninou Ph. | - | Aristotle University of Thessaloniki (GR) | Karakostas T. | - | Aristotle University of Thessaloniki (GR) |
| | 32p. |
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Dłużewski P., Young T.D., Dimitrakopulos G.♦, Komninou Ph.♦, Continuum and atomistic modelling of the mixed straight dislocation,
INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING, ISSN: 1543-1649, DOI: 10.1615/IntJMultCompEng.v8.i3.80, Vol.8, pp.331-342, 2010Streszczenie: A continuum and atomistic approach to the modeling of dislocations observed by high-resolution transmission electron microscopy (HRTEM) is discussed in terms of the continuum theory of dislocations. The atomistic models are obtained by means of the use of a mathematical formula for discrete dislocations. A new analytical solution for a continuously distributed dislocation core is presented. This solution is employed in the finite element modeling of residual stresses induced by the net of dislocations visible on an HRTEM image of GaN structure. This paper terminates with some comments on the atomistic/finite-element modeling of dislocation fields. Because of some confusion concerning notations used in the literature, the mathematical foundations of the continuum theory of dislocations are revisited. Słowa kluczowe: dislocations, field theory, atomistic models, finite element method, high-resolution transmission electron microscopy Afiliacje autorów:
Dłużewski P. | - | IPPT PAN | Young T.D. | - | IPPT PAN | Dimitrakopulos G. | - | Aristotle University of Thessaloniki (GR) | Komninou Ph. | - | Aristotle University of Thessaloniki (GR) |
| | 27p. |
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Young T.D., Kioseoglou J.♦, Dimitrakopulos G.P.♦, Dłużewski P., Komninou Ph.♦, 3D modelling of misfit networks in the interface region of heterostructures,
JOURNAL OF PHYSICS D-APPLIED PHYSICS, ISSN: 0022-3727, DOI: 10.1088/0022-3727/40/13/027, Vol.40, pp.4084-4091, 2007Streszczenie: We present a methodology for the stress–strain analysis of a film/substrate interface by combining crystallographic and continuum modelling. Starting from measurements of lattice parameters available from experimental observations, the heterostructure is recast initially in the form of a crystallographic model and finally as a continuum elastic model. The derived method is capable of handling dense arrays of misfit dislocations as well as large areas of the interface between two crystal structures. As an application we consider the misfit dislocation network in the GaN/Al2O3 interface region through determination of strain relaxation and associated residual stresses. Our calculated results are referred back to and found to be in good agreement with the experimental observations of misfit dislocation arrays obtained from high resolution transmission electron microscopy. Afiliacje autorów:
Young T.D. | - | IPPT PAN | Kioseoglou J. | - | Aristotle University of Thessaloniki (GR) | Dimitrakopulos G.P. | - | Aristotle University of Thessaloniki (GR) | Dłużewski P. | - | IPPT PAN | Komninou Ph. | - | Aristotle University of Thessaloniki (GR) |
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