Partner: Sławomir Kret

Institute of Physics, Polish Academy of Sciences (PL)

Recent publications
1.Wojnar P., Zieliński M., Janik E., Zaleszczyk W., Wojciechowski T., Wojnar R., Szymura M., Kłopotowski Ł., Baczewski L.T., Pietruchik A., Wiater M., Kret S., Karczewski G., Wojtowicz T., Kossut J., Strain-induced energy gap variation in ZnTe/ZnMgTe core/shell nanowires, APPLIED PHYSICS LETTERS, ISSN: 0003-6951, DOI: 10.1063/1.4873355, Vol.104, pp.163111-1-5, 2014
Abstract:

Strain-induced changes of ZnTe energy gap in ZnTe/ZnMgTe core/shell nanowires arising from lattice mismatch between the core and the shell semiconductor are studied by means of optical methods. It is shown that the increase of the Mg content in the shell, as well as the increase of the shell thickness result in an effective redshift of the near band edge photoluminescence from ZnTe nanowire cores, which reflects directly the decrease of energy gap under tensile strain conditions. The conclusions are supported by theoretical calculations in terms of the valence force field model. The observed change of ZnTe energy gap can be as large as 120 meV with respect to the unstrained conditions and can be tuned in a continuous manner by adjusting shell parameters, which open a path towards an effective band gap engineering in these structures.

Keywords:

Nanowires, II-VI semiconductors, Magnesium, Band gap, Quantum effects

Affiliations:
Wojnar P.-Institute of Physics, Polish Academy of Sciences (PL)
Zieliński M.-other affiliation
Wiater M.-Institute of Physics, Polish Academy of Sciences (PL)
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Karczewski G.-other affiliation
Wojtowicz T.-Institute of Physics, Polish Academy of Sciences (PL)
Kossut J.-Institute of Physics, Polish Academy of Sciences (PL)
Janik E.-other affiliation
Zaleszczyk W.-other affiliation
Wojciechowski T.-Institute of Physics, Polish Academy of Sciences (PL)
Wojnar R.-IPPT PAN
Szymura M.-other affiliation
Kłopotowski Ł.-other affiliation
Baczewski L.T.-Institute of Physics, Polish Academy of Sciences (PL)
Pietruchik A.-Institute of Physics, Polish Academy of Sciences (PL)
2.Nalepka K.T., Hoffman J., Kret S., Nalepka P., Szymański Z., Laser-deposited Cu/α–Al2O3 nanocomposite: experiment and modeling, APPLIED PHYSICS A-MATERIALS SCIENCE AND PROCESSING, ISSN: 0947-8396, DOI: 10.1007/s00339-014-8317-3, Vol.117, pp.169-173, 2014
Abstract:

A Nd:YAG laser operating at a wavelength of 266 or 355 nm is used to deposit a thin layer of copper on the (0 0 0 1)α-Al2O3 surface. The formation process is precisely controlled by identification of time distribution of two characteristics: energy and flux density of particles incident on the substrate. For this purpose, the Cu-plasma expansion is described by means of an analytical hydrodynamic model whose self-similar solutions are fitted to the experimental plasma images and time-of-flight spectra. The obtained nanocomposite is examined by the aberration-corrected high-resolution transmission electron microscopy (Cs-HRTEM) method. The results reveal that copper crystals assume one main orientation relative to the substrate (1 1 1)[2 −1 −1]Cu∥ (0 0 0 1)[−1 −1 2 0]α–Al2O3 and the formed interface has a specific microstructure. To reconstruct the phase boundary region, molecular dynamic (MD) and static (MS) simulations are carried out. The results show that strong bonding between copper and sapphire induces structural changes in the (1 1 1) Cu layer nearest the substrate and leads to formation of the system of partially dissociated dislocations in the next layer. In consequence, the Cu/α–Al2O3 interface becomes the semicoherent system. The lattice matching regions of the individual Cu layers are significantly lowered, which results in strong deformations along the closed packed planes. The reconstructed interface is used for Cs-HRTEM image simulation. A good accordance with the experimental results indicates that the MD model correctly maps the microstructure at the phase boundary of the synthesized nanocomposite.

Affiliations:
Nalepka K.T.-IPPT PAN
Hoffman J.-IPPT PAN
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Nalepka P.-Agriculture University in Krakow (PL)
Szymański Z.-IPPT PAN
3.Wojnar R., Wojnar P., Kret S., Elastic State Induced Energy Gap Variation in ZnTe/ZnMgTe Core/Shell Nanowires, TECHNISCHE MECHANIK, ISSN: 0232-3869, Vol.34, pp.233-245, 2014
Abstract:

The zinc telluride (ZnTe) nanowires grown recently are covered with the ZnMgTe shell. As a result of addition of magnesium the ZnMgTe lattice is expanded with respect to pure ZnTe lattice. From the lattice mismatch between the ZnMgTe shell and ZnTe nanowire core the internal strain and stress are created. Depending on the shell thickness and the Mg content in the shell the optical emission exhibits a considerable energy shift. To estimate this effect, at least qualitatively, the elastic state of the nanowire is calculated.

An analysis of the state of strain and stress in the core-shell nanowire within linear elasticity, using an analogy with thermal stresses is presented, in the similar way as it is applied, e.g. in hygro-mechanics. The suitable system of the differential Lame-Navier’s type equations is derived, and its solution for the axially symmetric problem is given. The jump of stress at the core-shell boundary is determined.

Affiliations:
Wojnar R.-IPPT PAN
Wojnar P.-Institute of Physics, Polish Academy of Sciences (PL)
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
4.Kret S., Dłużewski P., Szczepańska A., Żak M., Czernecki R., Kryśko M., Leszczyński M., Maciejewski G., Homogenous indium distribution in InGaN/GaN laser active structure grown by LP-MOCVD on bulk GaN crystal revealed by transmission electron microscopy and X-ray diffraction, NANOTECHNOLOGY, ISSN: 0957-4484, DOI: 10.1088/0957-4484/18/46/465707, Vol.18, No.46, pp.465707-0, 2007
Abstract:

We present transmission electron microscopy (TEM) and x-ray quantitative studies of the indium distribution in InxGa1−xN/GaN multiple quantum wells (MQWs) with x = 0.1 and 0.18. The quantum wells were grown by low-pressure metalorganic chemical vapour deposition (LP-MOCVD) on a bulk, dislocation-free, mono-crystalline GaN substrate. By using the quantitative TEM methodology the absolute indium concentration was determined from the 0002 lattice fringe images by the strain measurement coupled with finite element (FE) simulations of surface relaxation of the TEM sample. In the x-ray diffraction (XRD) investigation, a new simulation program was applied to monitor the indium content and lateral composition gradients. We found a very high quality of the multiple quantum wells with lateral indium fluctuations no higher than ΔxL = 0.025. The individual wells have very similar indium concentration and widths over the whole multiple quantum well (MQW) stack. We also show that the formation of 'false clusters' is not a limiting factor in indium distribution measurements. We interpreted the 'false clusters' as small In-rich islands formed on a sample surface during electron-beam exposure.

Affiliations:
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Dłużewski P.-IPPT PAN
Szczepańska A.-other affiliation
Żak M.-other affiliation
Czernecki R.-other affiliation
Kryśko M.-other affiliation
Leszczyński M.-other affiliation
Maciejewski G.-IPPT PAN
5.Maciejewski G., Kret S., Ruterana P., Piezoelectric field around threading dislocation in GaN determined on the basis of high-resolution transmission electron microscopy image, JOURNAL OF MICROSCOPY, ISSN: 0022-2720, Vol.223, pp.212-215, 2006
6.Jurczak G., Maciejewski G., Kret S., Dłużewski P., Ruterana P., Modelling of indium rich clusters in MOCVD InxGa1−xN/GaN multilayers, JOURNAL OF ALLOYS AND COMPOUNDS, ISSN: 0925-8388, DOI: 10.1016/j.jallcom.2004.05.038, Vol.382, No.1-2, pp.10-16, 2004
Abstract:

Chemical composition in a ternary alloy is examined using a quantitative high resolution transmission electron microscopy, finite element modelling of the thin foil relaxation phenomena and microscopy image simulation. The measurement of local lattice distortion on transmission electron microscopy images is a powerful tool for chemical composition determination. However, for the correct interpretation of the results, one needs to take into account the inhomogeneous relaxation of the sample and the strain averaging across the sample. The 3D finite element modelling of such phenomena have been performed as a function of chemical composition and geometry of an indium rich cluster in a MOCVD InxGa1−xN/GaN quantum well. Lattice distortion field measured on: experimental transmission electron microscopy image and simulated one, obtained on the basis of finite element simulation, are compared. This procedure allows an accurate determination of chemical composition in such heterostructures.

Keywords:

Indium clusters, Vapour deposition, Transmissionelectron microscopy, Elasticity, Finite element method, Lattice distortion, Image simulation

Affiliations:
Jurczak G.-IPPT PAN
Maciejewski G.-IPPT PAN
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Dłużewski P.-IPPT PAN
Ruterana P.-CNRS (FR)
7.Dłużewski P., Maciejewski G., Jurczak G., Kret S., Laval J.-Y., Nonlinear FE analysis of residual stresses induced by dislocations in heterostructures, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, DOI: 10.1016/j.commatsci.2003.10.012, Vol.29, No.3, pp.379-395, 2004
Abstract:

In this paper the field theory of dislocations is used in the finite element analysis of residual stresses in epitaxial layers. By digital processing of the HRTEM image of a GaAs/ZnTe/CdTe system the tensor maps of dislocation distribution are extracted. Such obtained maps are used as the input data to the finite element code. The mathematical foundations of this code are based on the compatibility equations for lattice distortions. The surface tension induced by misfit dislocations is considered here in terms of a 3D boundary-value problem for stress equilibrium in the interfacial zone. The numerical results show how strongly the surface tension depends on the nonlinear elastic behaviour of the crystal structure.

Keywords:

Microscopy and microanalysis techniques, Nonlinear elasticity, Dislocation structure, Finite element analysis, Residual stresses, Layered structures

Affiliations:
Dłużewski P.-IPPT PAN
Maciejewski G.-IPPT PAN
Jurczak G.-IPPT PAN
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Laval J.-Y.-CNRS (FR)

Conference papers
1.Ruterana P., Singh P., Kret S., Cho H.K., Lee H.J., Suh E.K., Jurczak G., Maciejewski G., Dłużewski P., Size and shape of In rich clusters and InGaN QWs at the nanometer scale, IWN 2004, International Workshop on Nitrides Semiconductors, 2004-06-19/06-23, Pittsburgh (US), DOI: 10.1002/pssc.200461463, Vol.2, No.7, pp.2381-2384, 2005
Abstract:

Following the need to accurately understand the In composition fluctuations and their role on the optical properties of the GaN based heterostructures, an investigation of MOCVD InGaN/GaN quantum wells is carried out. To this end, quantitative High Resolution Transmission Electron Microscopy (HRTEM) is coupled with image simulation and Finite Element Method (FEM) for the thin foil relaxation modelling. The results show that the indium content can reach x = 1 in the clusters inside the core. In these MOCVD QWs, we attempt to connect the Quantum dot density, composition, and shape to the growth conditions, in order to help the engineering process of highly efficient devices.

Affiliations:
Ruterana P.-CNRS (FR)
Singh P.-CNRS (FR)
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Cho H.K.-Dong-A University (KR)
Lee H.J.-Chonbuk National University (KR)
Suh E.K.-Chonbuk National University (KR)
Jurczak G.-IPPT PAN
Maciejewski G.-IPPT PAN
Dłużewski P.-IPPT PAN

Conference abstracts
1.Pęcherski R.B., Nalepka K.T., Nalepka P., Sztwiertnia K., Kret S., Ustrzycka A., Assessment of the strength of nanocomposites based on interface bonding analysis, ICTAM XXIV, 24th International Congress of Theoretical and Applied Mechanics, 2016-08-21/08-26, Montréal (CA), pp.2384-2385, 2016
Abstract:

Recent investigations reveal that interface bonding strength is dependent on the relative orientation of crystallites of the both phases [2]. The experimental, theoretical and computational investigations confirm this observation in the case of Cu/Al2O3 system, [3], [4]. It is shown that the statistical distribution of the values of interface strength for different relative orientations of bonded phases should be included in the phenomenological model of the damage initiation in nanocomposites. The novelty of the presented study is the combination of different experimental techniques: HRTEM, EBSD and molecular dynamics simulations with phenomenological theory of damage development in nanocomposites due to debonding at the interphase boundary [5], [6], [7]. A class of new models with the yield condition determined by one of quadric surfaces, in particular paraboloid or ellipsoid one is considered and the comparison with popular Gurson approach is discussed, [8].

Keywords:

nanocompistes, strength, interface, bonding, HRTEM, EBSD, molecular dynamics

Affiliations:
Pęcherski R.B.-IPPT PAN
Nalepka K.T.-IPPT PAN
Nalepka P.-Agriculture University in Krakow (PL)
Sztwiertnia K.-other affiliation
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Ustrzycka A.-IPPT PAN
2.Kret S., Bilska M., Ivaldi F., Leszczyński M., Czernecki R., Dłużewski P., Jurczak G., Young T.D., Determination of the nanoscale structural properties of the InAlN based devices by advanced TEM methods, E-MRS 2012 FALL MEETING, 2012-09-17/09-21, Warszawa (PL), 2012
Keywords:

III-V semiconductors, piezoelectricity, high resolution transmission electron microscopy, band edge structure

Affiliations:
Kret S.-Institute of Physics, Polish Academy of Sciences (PL)
Bilska M.-other affiliation
Ivaldi F.-other affiliation
Leszczyński M.-other affiliation
Czernecki R.-other affiliation
Dłużewski P.-IPPT PAN
Jurczak G.-IPPT PAN
Young T.D.-IPPT PAN
3.Maździarz M., Nalepka K.T., Szymański Z., Hoffman J., Kret S., Kucharski S., Nalepka P., Atomistic Model of Decohesion of Copper-Corundum Interface, SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.204-205, 2012