A. Sweyllam

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Kagoshima University

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Jadavpur University, Kolkata, India

Suman Paul

Presidency University, Bengaluru

Subrata Ghosh

Indira Gandhi Centre for Atomic Research

Hendra Grandis

Institut Teknologi Bandung

Michel Gregoire

Observatoire Midi-Pyrénées, Université de Toulouse III Paul Sabatier

Ramazan Demirtaş

Ankara University

Atanas G Atanasov

Medical University of Vienna

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Universidade de São Paulo

Magdalena Titirici

Queen Mary, University of London

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Papers by A. Sweyllam

INTERFACE STATES-INDUCED-CHANGE IN THE ENERGY BAND DIAGRAM AND CAPACITANCE–VOLTAGE CHARACTERISTICS OF ISOTYPE ZnTe/CdTe HETEROJUNCTIONS

International Journal of Modern Physics B, 2010

ABSTRACT Epitaxial layers of ZnTe have been grown on a (111) oriented CdTe single crystal substra... more ABSTRACT Epitaxial layers of ZnTe have been grown on a (111) oriented CdTe single crystal substrate by thermal evaporation technique at 180°C and a pressure of 10-6 Torr. X-ray diffraction pattern indicated a highly oriented crystallographic growth of ZnTe (111) layer on CdTe (111) substrate. C–V measurements are carried out at frequencies of 10 kHz and 100 kHz. 1/C2 versus the forward bias voltage gave a straight line in the voltage range from 1 to 3 V. Extrapolation of 1/C2 → 0 led to an estimated value of the built-in potential of about 0.58 V. The calculated charge carrier concentration in the lightly doped over-grown layer, ZnTe, has been found to be p = 1.7 × 1016cm-3. It was found that energy band diagram constructed according to the electron affinity model is not the adequate one to explain the capacitance–voltage behavior. Therefore, one should take into account the effect of interface states on the energy band diagram. The interface states density has been estimated to be ~1013cm-2 for (111) ZnTe/(111)CdTe heterojunction system. The interface states were identified as hole traps for the ZnTe/CdTe heterojunction. Accordingly, a band bending downward both materials, and a depletion zone in both of them are expected.

Electrical Properties Of Modulation Doped Si/SiGe Heterostructures Grown On Silicon On Insulator Substrates

We report on the growth and characterization of high-mobility 2DEGs on tensile strained Si grown ... more We report on the growth and characterization of high-mobility 2DEGs on tensile strained Si grown on cubic SiGe alloy on SOI substrates. The electrical properties were investigated in the 4.2-300 K temperature range as a function of growth conditions and sample structure. Hall mobilities as high as 82000 cm2/V.s at T=4.2 K were obtained in the best 2DEGs on SOI.

Growth and current–voltage characterization of ZnTe/CdTe heterojunctions

Thin Solid Films, 2010

ZnTe layers have been grown on a (111) oriented CdTe single crystal substrate by vacuum thermal e... more ZnTe layers have been grown on a (111) oriented CdTe single crystal substrate by vacuum thermal evaporation technique. The growth temperature was 180°C at a base pressure of 10 − 4 N/m 2 . The as-grown samples were investigated by X-ray diffraction. The pattern indicated a highly oriented crystallographic growth of ZnTe (111) layer on CdTe substrate. The current-voltage characteristics in both forward and reverse biasing were carried out in the temperature range from 300 down to 200 K. The dark forward current curves were definitely of the diode type in the forward direction. This behavior can be understood as the barrier at the interface limits forward and reverse carrier flow across the junction, where the built-in potential could be developed. Series resistance due to the neutral region was estimated at approximately 320 Ω and the activation energy of the carriers was calculated and found to be 0.11 ± 0.03 eV. The reverse current shows negative resistance behavior at low voltage range.

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Optical properties of Se–Te–Sb thin films

Canadian Journal of Physics, 2014

Influence of substrate temperature on electrical and optical properties of p-type semitransparent conductive nickel oxide thin films deposited by radio frequency sputtering

Applied Surface Science, 2008

Nickel oxide thin films were deposited on fused silica and Si(1 0 0) substrates at different subs... more Nickel oxide thin films were deposited on fused silica and Si(1 0 0) substrates at different substrate temperatures ranging from room temperature to 400 8C using radio frequency reactive magnetron sputtering from a Ni metal target in a mixture of O 2 and Ar. With the increase of substrate temperature, nickel oxide films deposited on the Si substrates exhibit transition from amorphous to poly-crystalline structures with different preferred orientations of NiO(2 0 0) and . The films deposited at higher temperature exhibit higher Ni 2+ /Ni 3+ ratio. With substrate temperature increasing from room temperature to 400 8C, the electrical resistivities of nickel oxide films increase from (2.8 AE 0.1) Â 10 À2 to (8.7 AE 0.1) V cm, and the optical band-gap energies increase from 3.65 to 3.88 eV. A p-nickel oxide/n-zinc oxide heterojunction was fabricated to confirm the p-type conduction of nickel oxide thin film, which exhibited a steadily rectifying behavior. #

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Polyamides nanoparticles containing flexible linkages and their copper complexes with novel dielectric properties: Structure–property relationship

by Hammed Hassan and A. Sweyllam

Journal of Molecular Structure, 2011

We report the chemistry of nanometer-sized spherical aramides nanoparticles and their copper comp... more We report the chemistry of nanometer-sized spherical aramides nanoparticles and their copper complexes as novel types of hybrids nanomaterials. Based on the flexible linkage type, the average diameters of the nanoparticles-containing sulfone or ether linkage were 140 nm and 190 nm, respectively, as judged by the scanning electron microscopy (SEM) photographs. Incorporation of copper (II) ions into these particles furnished polymeric complexes in (1:2) ratios with square planar geometries. The polymeric structures were proved on the basis of their IR, UV, ESR and elemental analysis data. The thermal properties of the polymers were evaluated by various techniques and results revealed the high thermal stabilities of the hybrids. The calculated limiting oxygen index (LOI) indicates that such macromolecules can be classified as self-extinguishing polymers. The dc electrical conductivity of all samples indicates either semiconducting or metal-like nature in the regime of semiconductor behaviors. Incorporation of copper significantly improved the conductivity of the resulting complexes due to the enhanced mobility of the charge carriers upon doping. Dielectric losses are characterized by sharp peaks appearing at characteristic frequencies suggesting the presence of relaxing dipoles. The peak positions did not change with temperature indicating a non-activated process. The loss tangent increased with frequency and the peaks shifted toward the lower frequency upon doping suggesting the increase in the energy loss ratio compared to the energy storage in the dielectric. The higher value of dielectric loss at low frequency is due to the free charge motion within the materials. The reported dielectric results revealed anomalous behaviors which have not been reported earlier in similar hybrids.

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INTERFACE STATES-INDUCED-CHANGE IN THE ENERGY BAND DIAGRAM AND CAPACITANCE–VOLTAGE CHARACTERISTICS OF ISOTYPE ZnTe/CdTe HETEROJUNCTIONS

International Journal of Modern Physics B, 2010