Wojciech Szuszkiewicz  Michel Jouanne  Jean‐Franois Morhange  Makoto Kanehisa  Elbieta Dynowska  Katarzyna Gas  Elbieta Janik  Grzegorz Karczewski  Rafa&#x; Kuna  Tomasz Wojtowicz 《physica status solidi b》2014,251(6):1133-1143

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Tomasz J. Antosiewicz  Carl Wadell  Christoph Langhammer 《Advanced Optical Materials》2015,3(11):1654-1654

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Grzegorz Luka  Tomasz Krajewski  Lukasz Wachnicki  Bartlomiej Witkowski  Elzbieta Lusakowska  Wojciech Paszkowicz  Elzbieta Guziewicz  Marek Godlewski 《physica status solidi (a)》2010,207(7):1568-1571

Atomic layer deposition (ALD) was used to fabricate transparent and conductive thin films of ZnO. Two hundred‐nano metre thick ZnO films were deposited on glass substrates at low growth temperatures varied between 120 and 240 °C. As zinc and oxygen precursors we used diethylzinc (DEZn) and deionized water, respectively. To find optimal film parameters, the structure, surface morphology, optical and electrical measurements were carried on. The films obtained at 200 °C show the highest carrier concentration (∼10²⁰ cm⁻³) and the lowest resistivity (2 × 10⁻³ Ω cm). The films exhibit mobilities up to 37 cm²/Vs that we associate to the process technology used. An important point of our approach was that the films studied were not intentionally doped (with Al or other group III elements) but the high electrical conductivity was achieved by playing with the sample stoichiometry and growth conditions.  相似文献   

    

Tomasz Strek  Hubert Jopek 《physica status solidi b》2012,249(7):1359-1365

Materials with unusual mechanical properties can be potentially used as matrices to create high‐performance lightweight composites. The appearance of materials with negative Poisson's ratio (auxetics), has led to the evaluation of auxetic composites for possible engineering applications. Because the experimental evaluation of composites with specific properties is expensive and time consuming, computational modelling and simulation provide efficient alternatives to predict the parameters of the composites. In this paper a finite element method was used to find the engineering constants (Young's modulus and Poisson's ratio) of auxetic composites consisting of concentric cylindrical inclusions made of combinations of auxetic and classic (non‐auxetic) materials. It has been observed that not only the mechanical properties of the different composite phases influence the effective mechanical properties of the whole composite, but also the location of the same material phases do matter.  相似文献   

    

Dr. Andrea Ehrmann  Professor Tomasz Błachowicz 《Physik in unserer Zeit》2012,43(3):124-127

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Kamil Gradkowski  Tomasz J. Ochalski  David P. Williams  Sorcha B. Healy  Jun Tatebayashi  Ganesh Balakrishnan  Eoin P. O'Reilly  Guillaume Huyet  Diana L. Huffaker 《physica status solidi b》2009,246(4):752-755

We present a detailed explanation of the blue‐shift that is observed in Ga(As)Sb quantum dots (QD) with increasing pump power density by employing an 8‐band k · p model with the Coulomb attractive potential added into the Hamiltonian. Two types of structures are considered: Ga(As)Sb QDs in a GaAs matrix and the same dots overgrown with an InGaAs quantum well (QW). We show that with increasing charge density the electron and hole energy levels shift relative to each other, which results in an increase of the optical transition energy (i.e. a blue‐shift). The major contribution to the effect arises from the holes and is a result of their 3D confinement inside the dot. Additionally, with increasing charge density the electrons move closer to the dot, which improves the oscillator strength of the ground‐state optical transition. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Tomasz Czyszanowski  Micha&#x; Wasiak  Robert P. Sarza&#x;a  W&#x;odzimierz Nakwaski 《physica status solidi (a)》2007,204(10):3562-3573

Modern small‐size vertical‐cavity surface‐emitting diode lasers (VCSELs) require principally fully vectorial optical modelling because their cavity sizes are of the order of the wavelength of emitted radiation. However, much simpler scalar approaches are often surprisingly exact even beyond the limits of their confirmed validity. Therefore, in the present paper, reasonable limits of an application of simplified scalar optical approaches (instead of more exact but also much more involved and time‐consuming rigorous vectorial ones) are determined to model threshold operation of possible nitride VCSELs equipped with tunnel junctions with the aid of a comparison of results of the scalar effective frequency method with those obtained using the fully vectorial three‐dimensional plane wave admittance method. Both these optical methods have been found to give usually quite close results for the fundamental transverse mode. Larger discrepancies between the results of both approaches have been found for first‐order transverse modes (and even larger are expected for higher‐order ones) and for larger (or very small) active regions. Some structural modifications of nitride VCSELs, which may enable their low‐threshold single‐fundamental‐mode room‐temperature continuous‐wave operation, are proposed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Víctor M. García‐Surez  Tomasz Kostyrko  Steven Bailey  Colin Lambert  Bogdan R. Bu&#x;ka 《physica status solidi b》2007,244(7):2443-2447

We consider a model of a molecular junction made of BDT (benzene dithiol) molecule trapped between two Au(100) leads. Using the ab initio approach implemented in the SIESTA package we look for the optimal configurations of the molecule as a function of the distance between the leads. We find that for distances long enough the energy of the system is minimized when the molecule is bonded asymmetrically, i.e. chemisorbed to one of the leads, whereas for distances shorter than 12 Å the energy is minimized when the molecule sits in the middle between the leads. We discuss possible consequences of the above findings for the transport properties of the junction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

    

Ma&#x;gorzata I. &#x;ukasiewicz  Bart&#x;omiej Witkowski  Marek Godlewski  Elbieta Guziewicz  Maciej Sawicki  Wojciech Paszkowicz  Rafa&#x; Jakie&#x;a  Tomasz A. Krajewski  Grzegorz &#x;uka 《physica status solidi b》2010,247(7):1666-1670

In the present study we report on properties of ZnCoO films grown at relatively low temperature by the atomic layer deposition, using two reactive organic zinc precursors (dimethylzinc and diethylzinc). The use of these precursors allowed us the significant reduction of a growth temperature to below 300 °C. The influence of growth conditions on the Co distribution in ZnCoO films, their structure and magnetic properties was investigated using secondary ion mass spectroscopy, scanning electron microscopy, cathodoluminescence, energy dispersive X‐ray spectrometry (EDX), X‐ray diffraction and superconducting quantum interference device magnetometry. We achieved high uniformity of the films grown at 160 °C. Such films are paramagnetic. Films grown at 200 °C and at higher temperature are nonuniform. Formation of foreign phases in such films was detected using high resolution EDX method. These samples are not purely paramagnetic and show weak ferromagnetic response at low temperature.  相似文献   

    

Danuta Rasa&#x;a  Tomasz B&#x;k  Erkki Kolehmainen  Stanis&#x;aw Styrcz  Ryszard Gawinecki 《Journal of Physical Organic Chemistry》1996,9(9):631-638

Substituent effects on the ¹³C NMR spectra of 4-aryl-2,6-diphenylpyrylium and 1-methyl-4-aryl-2,6-diphenylpyridinium perchlorates and 4-aryl-2,6-diphenylpyridines were investigated. The dual substituent parameter approach indicates that the resonance contribution to the carbon chemical shifts in the para position to the substituent in the 4-aryl moiety is comparable to that for 4-R-biphenyls. Although heterocyclic moieties jointed at the para position with respect to the substituent in the 4-aryl group differ in their deactivating power, they diminish the resonance term to the same extent in each series. This may result in conformational variations of the compounds studied. AM1 calculations were used to explain the chemical shifts observed.  相似文献