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Effect of AlN intermediate layer on growing GaN film by hydride vapor phase epitaxy

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Rare Metals 2006年第Z2期25卷 15-19页

作者： NOUet Gérard2 RUTERANA Pierre laboratoire structures des interfaces et fonctionnalité des couches minces UMR CNRS 6176 ENSICAEN6 Boulevard du Maréchal Juin 14050 Caen Cedex France

Thick GaN layer deposited by hydride vapor phase epitaxy (HVPE) on a metalorganic chemical vapor deposition (MOCVD) GaN template with a thin low temperature (LT) AlN intermediate layer was investigated. High resolution X-ray resolution diffraction (HRXRD) shows that the crystalline quality of thick GaN layer was improved compared with the template. As confirmed by atomic force microscopy (AFM) observations, the surface morphology of AlN intermediate layer helps to improve the nucleation of GaN epilayer. Photoluminescence (PL) spectra measurement shows its high optical quality and low compressive stress, and micro Raman measurement confirms the latter result. Thus, the deposition of the LT-AlN interlayer has promoted the growth of an HVPE-GaN layer with an excellent crystalline quality.

关键词： GaN AlN intermediate layer HVPE HRXRD AFM photoluminescence

Growth of high-quality thick GaN using a tungsten interlayer

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Rare Metals 2006年第Z2期25卷 11-14页

作者： NOUet Gérard RUTERANA Pierre laboratoire structures des interfaces et fonctionnalité des couches minces UMR CNRS 6176 ENSICAEN 6 Boulevard du Maréchal Juin 14050 Caen Cedex France

A high-quality GaN film was (W-GaN) grown by hydride vapor phase epitaxy (HVPE) on metalorganic chemical vapor deposition (MOCVD) GaN templates with a tungsten (W) interlayer. A sample without interlayer was also grown at the same time for comparison. Significant reductions of dislocation density in W-GaN film is confirmed by the result of high-resolution X-ray diffraction and transmission electron microscope (TEM) observation. The improvement of optical properties of the W-GaN is confirmed by photoluminescence (PL) result. A shift of PL peak suggests that the strain is lower in the W-GaN than the film without W interlayer. This technique offers a potential path to obtain high-quality GaN film as free-standing substrate.

关键词： GaN tungsten interlayer HVPE HRXRD

Properties of n-type SnO_2 semiconductor prepared by spray ultrasonic technique for photovoltaic applications

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Journal of Semiconductors 2015年第12期36卷 34-37页

作者： H.Bendjedidi A.Attaf H.Saidi M.S.Aida S.Semmari A.Bouhdjar Y.Benkhetta laboratoire de Physique des couches minces et Applications Université de Biskra laboratoire des couches minces et interfaces Université Mentouri

Transparent conducting n-type SnO2 semiconductor films were fabricated by employing an inexpensive, simplified spray ultrasonic technique using an ultrasonic generator at deferent substrate temperatures （300, 350, 400, 450 and 500 ℃）. The structural studies reveal that the SnO2 films are polycrystalline at 350,400, 450, 500 ℃ with preferential orientation along the （200） and （101） planes, and amorphous at 300 ℃. The crystallite size of the films was found to be in the range of 20.9-72.2 nm. The optical transmittance in the visible range and the optical band gap are 80% and 3.9 eV respectively. The films thicknesses were varied between 466 and 1840 nm. The resistivity was found between 1.6 and 4 × 10^-2 Ω.cm. This simplified ultrasonic spray technique may be considered as a promising alternative to a conventional spray for the massive production of economic SnO2 films for solar cells, sensors and opto-electronic applications.

关键词： tin oxide thin films spray ultrasonic structural properties optical properties

Surface morphology and electrochemical characterization of electrodeposited Ni-Mo nanocomposites as cathodes for hydrogen evolution

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Chinese Physics B 2015年第10期24卷 559-563页

作者： Elhachmi Guettaf Temam Hachemi Ben Temam Said Benramache laboratoire de Physique des couches minces et Applications Université de Biskra

In this work, we study the influences of current density on surface morphology and electrochemical characterization of electrodeposited Ni-Mo. The Ni-Mo composite coatings are deposited on pretreated copper substrates by electrolytic deposition. The Ni-Mo solution is taken from nickel sulfate fluid and ammonium heptamolybdate with 10 g/l. The Ni-Mo composite coatings are deposited at a temperature of 303 K with an applied current density of j dep= 10 A/dm2-30 A/*** find that the corrosion resistance is improved by incorporating Mo particles into Ni matrix in 0.6-M Na Cl solution. From the potentiodynamic polarization curve of electrodeposited Ni-Mo it is confirmed that the corrosion resistance decreases with increasing applied current density. The x-ray diffraction（XRD） analyses of Ni-Mo coatings indicate three phases of Mo Ni4, Mo1.24Ni0.76, and Ni3 Mo phases crystallites of nickel and molybdenum. The scanning electronic microscopy（SEM） tests indicate that Ni-Mo coatings present cracks and pores.

关键词： Ni-Mo electrolytic deposition corrosion resistance potentiodynamic polarization plating current density

Effect of SnCl2 and SnCl4 precursors on SnSx thin films prepared by ultrasonic spray pyrolysis

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Journal of Semiconductors 2017年第6期38卷 18-23页

作者： Z.Hadef K.Kamli A.Attaf M.S.Aida B.Chouial laboratoire des Semi-Conducteurs Faculte des Sciences Universite Badji Mokhtar Annaba Algeria laboratoire de physique des couches minces et applications LPCMA Universite de Biskra Algeria laboratoire de couches minces et interfaces Faculte des Sciences Universite de Constantine Algeria

Thin films of SnSx,semiconductors,have been successfully synthesized by ultrasonic spray pyrolysis technique,using two precursors namely：tin（II）chloride and tin（IV）chloride,*** solutions were prepared by the dilution of different Sn molarities of the two precursors *** precursor molarities were varied from 0.04 to 0.07 mol/L,whereas that of S was fixed at 0.1 mol/*** present work focuses on the effect of the different precursor’s molarities on the nature and the properties of the prepared thin films in order to optimize the growth conditions.X-ray diffraction analysis reveals that the precursor’s molarities alter the grain size of the prepared films,which varied from 8 to 14 nm and from 12 to 16 nm,according to the used *** films analysis by SEM,shows that the SnS2 films are more dense and smooth than the SnS *** composition of the elements is analysed with an EDX spectrometer,and the obtained result for M（sn）=0：07 mol/L indicates that the atomic ratio of Sn to S is 51.57：48：43 and 36：64 for films synthesized from the first and second precursors *** measurements show that the conductivity behavior depends on the used precursors and their molarities.

关键词： precursors ultrasonic spray tin sulfide semiconductor thin films characterization

Optoelectronic properties of SnO2 thin films sprayed at different deposition times

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Chinese Physics B 2016年第4期25卷 296-302页

作者： Allag Abdelkrim Saad Rahmane Ouahab Abdelouahab Attouche Hafida Kouidri Nabila laboratoire de Physique des couches minces et Applications Universit de Biskra BP 145 RP 07000 Biskra Alg&ie

This article presents the elaboration of tin oxide （SnO2） thin films on glass substrates by using a home-made spray pyrolysis system. Effects of film thickness on the structural, optical, and electrical film properties are investigated. The films are characterized by several techniques such as x-ray diffraction （XRD）, atomic force microscopy （AFM）, ultraviolet- visible （UV-Vis） transmission, and four-probe point measurements, and the results suggest that the prepared films are uniform and well adherent to the substrates. X-ray diffraction （XRD） patterns show that SnO2 film is of polycrystal with cassiterite tetragonal crystal structure and a preferential orientation along the （110） plane. The calculated grain sizes are in a range from 32.93 nm to 56.88 nm. Optical transmittance spectra of the films show that their high transparency average transmittances are greater than 65% in the visible region. The optical gaps of SnO2 thin films are found to be in a range of 3.64 eV-3.94 eV. Figures of merit for SnO2 thin films reveal that their maximum value is about 1.15 x 10-4 Ω-1 at λ = 550 nm. Moreover, the measured electrical resistivity at room temperature is on the order of 10^-2 Ω.cm.

关键词： thin film SnO2 spray pyrolysis thickness properties

Atomic core structure of 90°c■bent screw threading dislocations in wurtzite GaN

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Rare Metals 2006年第S2期25卷 1-4页

作者： BELABBAS Imad RUTERANA Pierre NOUet Gérard laboratoire Structure des interfaces et fonctionnalité des couches minces UMR CNRS 6176 Ecole Nationale Supérieure d′Ingénieurs de Caen 6 Bld du Maréchal Juin 14050 Caen cedex France

The atomic and electronic structures of the c threading dislocations with an edge or screw character were compared using a tight binding formalism which takes into account charge transfer. The two dislocations do not exhibit dangling bonds. While the screw dislocation contains only constrained Ga-N bonds, the edge dislocation contains Ga-Ga and N-N wrong bonds. Both dislocations are found to induce shallow and deep gap states.

关键词： GaN dislocations SCC-DFTB

The calculation of band gap energy in zinc oxide films

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Journal of Semiconductors 2015年第1期36卷 17-22页

作者： Ali Arif Okba Belahssen Salim Gareh Said Benramache Electrical Engineering Department Faculty of Technology University of Biskra Algeria laboratoire de Physique des couches minces et Applications (LPCMA) Université de Biskra Algeria Mechanical Engineering Department Faculty of Technology University of Biskra Algeria

We investigated the optical properties of undoped zinc oxide thin films as the n-type semiconductor;the thin films were deposited at different precursor molarities by ultrasonic spray and spray pyrolysis *** thin films were deposited at different substrate temperatures ranging between 200 and 500℃. In this paper, we present a new approach to control the optical gap energy of ZnO thin films by concentration of the ZnO solution and substrate temperatures from experimental data, which were published in international journals. The model proposed to calculate the band gap energy with the Urbach energy was investigated. The relation between the experimental data and theoretical calculation suggests that the band gap energies are predominantly estimated by the Urbach energies, film transparency, and concentration of the ZnO solution and substrate temperatures. The measurements by these proposal models are in qualitative agreements with the experimental data; the correlation coefficient values were varied in the range 0.96–0.99999, indicating high quality representation of data based on Equation（2）, so that the relative errors of all calculation are smaller than 4%. Thus, one can suppose that the undoped ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition and contained higher optical band gap energy.

关键词： ZnO thin films semiconductor band gap energy correlation

Influences of graphene nanoplatelet aspect ratio and thermal treatment on dielectric performances of poly(methyl methacrylate)composites

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High Voltage 2016年第4期1卷 146-150页

作者： Benhui Fan Yu Liu Delong He Jinbo Bai laboratoire Mécanique des Sols Structures et Matériaux(MSSMat)CNRS UMR 8579Ecole CentraleSupelecUniversitéParis SaclayGrande Voie des Vignes92290 Chatenay-MalabryFrance

The dielectric property and percolated behaviour of polymer matrix composites largely depend on the morphology of conductive fillers and external stimulations especially when the composites are processed by melting blending and extrusion-injection *** this study,the poly(methyl methacrylate)(PMMA)matrix composites incorporated by two kinds of graphene nanoplatelets(GNP),G5 and G150 with different aspect ratios(the ratio of diameter and thickness)are prepared to study the influence of GNP morphology on the dielectric performances close to percolation threshold(f_(c)).After annealing at glass transition temperature(T_(g))for 1 h,the dielectric permittivities of PMMA/G5 and PMMA/G150 near fc increase 43 and 38%,respectively,while the dielectric loss change *** improvement on the dielectric property is possibly attributed to the slight change of the distance between adjacent GNPs after annealing at T_(g)which enables to arouse stronger polarisation by tunnelling effect.

关键词： composites dielectric property