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CONTENTS
Volume 3, Number 1, March 2015
 

Abstract
Thin film ethanol sensors made from a-Fe2O3 decorated with multiwall carbon nanotubes (MWCNTs) were manufactured by the electron beam deposition method. The morphology of the decorated a-Fe2O3/MWCNTs (25:1 weight ratios) nanocomposite powder was investigated using the scanning electron microscopy and X-ray diffraction techniques. The thickness of thin films has been determined from ellipsometric measurements. The response of manufactured sensors was investigated at different temperatures of the sensor work body and concentration of gas vapors. Good response of prepared sensors to ethanol vapors already at work body temperature of 150oC was shown.

Key Words
gas sensor; Fe2O3; carbon nanotubes; response; ethanol

Address
Vladimir M. Aroutiounian, Valeri M. Arakelyan, Gohar E. Shahnazaryan, Mikayel S. Aleksanyan: Centres of Semiconductor Devices and Nanotechnologies, Yerevan State University, 1 Alek Manookian St., 0025 Yerevan, Armenia
Klara Hernadi, Zoltan Nemeth, Peter Berki: Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, Szeged H-6720, Hungary
Zsuzsanna Papa, Zsolt Toth: Department of Optics and Quantum Electronics, University of Szeged, Dom tér 9, Szeged H-6720, Hungary
Laszlo Forro: Laboratory of Physics of Complex Matter, Ecole Polytechnique Federale de Lausanne, Lausanne, CH-1015, Switzerland

Abstract
Size dependent emission properties and the interband optical transition energies in group-III nitride based quantum dots are investigated taking into account the geometrical confinement. Exciton binding energy and the optical transition energy in Ga0.9In0.1N/GaN and Al0.395In0.605N /AlN quantum dots are studied. The largest intersubband transition energies of electron and heavy hole with the consideration of geometrical confinement are brought out. The interband optical transition energies in the quantum dots are studied. The exciton oscillator strength as a function of dot radius in the quantum dots is computed. The interband optical absorption coefficients in GaInN/GaN and AlInN/AlN quantum dots, for the constant radius, are investigated. The result shows that the largest intersubband energy of 41% (10%) enhancement has been observed when the size of the dot radius is reduced from 50 A to 25 A of Ga0.9In0.1N/GaN (Al0.395In0.605N /AlN) quantum dot.

Key Words
oscillator strength; exciton; quantum dot

Address
K. Jaya Bala: Department of Physics, GTN Arts College, Dindigul-624 005, India
A. John Peter: P.G & Research Department of Physics, Government Arts College, Melur-625 106, Madurai, India

Abstract
In the current study, the nonlinear vibration properties of an embedded zigzag single-walled carbon nanotube (SWCNT) are investigated. Winkler-type model is used to simulate the interaction of the zigzag SWCNTs with a surrounding elastic medium. The relation between deflection amplitudes and resonant frequencies of the SWCNT is derived through harmonic balance method. The equivalent Young\'s modulus and shear modulus for zigzag SWCNT are derived using an energy-equivalent model. The amplitude – frequency curves for large-amplitude vibrations are graphically illustrated. The simulation results show that the chirality of zigzag carbon nanotube as well as surrounding elastic medium play more important roles in the nonlinear vibration of the single-walled carbon nanotubes.

Key Words
zigzag carbon nanotube; nonlinear vibration; harmonic balance method

Address
Abderrahmane Besseghier: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria; Centre Universitaire de Tissemsilt, Algeria
Houari Heireche: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria
Abdelmoumen Anis Bousahla: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria; Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
Abdelouahed Tounsi: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria; Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria; Laboratoire des Structures et Materiaux Avances dans le Genie Civil et Travaux Publics,
Faculte de Technologie, Département de Genie Civil, Universite de Sidi Bel Abbes, Algerie
Abdelnour Benzair: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria; Algerian National Thematic Agency of Research in Science and Technology (ATRST), Algeria

Abstract
We study a device structure which can be used to generate pure valley current and valley polarized current using quantum adiabatic pumping. The design of the structure allows the flexibility of changing the structure from one for pure valley current generation to one for valley polarized current generation by changing the applied electric potentials through changing the symmetry of the structure. The device is useful for the development of valleytronic devices.

Key Words
nano-physics; nano-devices; nano-science; nano-tech; nano-carbon

Address
Jing Wang: The Key Lab of RF Circuits and Systems of Ministry of Education of China, Hangzhou Dianzi University, Zhejiang, China; Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, P.R. China
K.S. Chan: Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR, P.R. China; City University Shenzhen Research Institute, Shenzhen, P.R. China

Abstract
The structure represents symmetrical metal electrode (gate 1) – front SiO2 layer – n-Si nanowire FET – buried SiO2 layer – metal electrode (gate 2). At the symmetrical gate voltages high conductive regions near the gate 1 – front SiO2 and gate 2 – buried SiO2 interfaces correspondingly, and low conductive region in the central region of the NW are formed. Possibilities of applications of nanosize FETs at the deep inversion and depletion as a distributed capacitance are demonstrated. Capacity density is an order to ~uF⁄cm2 . The charge density, it distribution and capacity value in the nanowire can be controlled by a small changes in the gate voltages. at the non-symmetrical gate voltages high conductive regions will move to corresponding interfaces and low conductive region will modulate non-symmetrically. In this case source-drain current of the FET will redistributed and change current way. This gives opportunity to investigate surface and bulk transport processes in the nanosize inversion channel.

Key Words
quantization; charge modulation; nanosize FET; capacity

Address
Ferdinand V. Gasparyan and Vladimir M. Aroutiounian: Department of Semiconductor Physics and Microelectronics, Yerevan State University, 1 Alex Manoogian St., Yerevan 0025, Armenia



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