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CONTENTS
Volume 2, Number 1, March 2014
 

Abstract
Dislocations are basic crystal defects and represent one-dimensional native nanostructures embedded in a perfect crystalline matrix. Their structure is predefined by crystal symmetry. Twodimensional, self-organized arrays of such nanostructures are realized reproducibly using specific preparation conditions (semiconductor wafer direct bonding). This technique allows separating dislocations up to a few hundred nanometers which enables electrical measurements of only a few, or, in the ideal case, of an individual dislocation. Electrical properties of dislocations in silicon were measured using MOSFETs as test structures. It is shown that an increase of the drain current results for nMOSFETs which is caused by a high concentration of electrons on dislocations in p-type material. The number of electrons on a dislocation is estimated from device simulations. This leads to the conclusion that metallic-like conduction exists along dislocations in this material caused by a one-dimensional carrier confinement. On the other hand, measurements of pMOSFETs prepared in n-type silicon proved the dominant transport of holes along dislocations. The experimentally measured increase of the drain current, however, is here not only caused by an higher hole concentration on these defects but also by an increasing hole mobility along dislocations. All the data proved for the first time the ambipolar behavior of dislocations in silicon. Dislocations in p-type Si form efficient one-dimensional channels for electrons, while dislocations in n-type material cause onedimensional channels for holes.

Key Words
dislocations; one-dimensional nanostructures; electronic properties; MOSFETs; semiconductor wafer bonding

Address
Manfred Reiche, Eckhard Pippel and Sigrid Hopfe : Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany
Martin Kittler : IHP Microelectronics, Im Technologiepark 25, D-15236 Frankfurt (Oder), Germany
Hartmut Uebensee : CIS Research Institute of Microsensorics and Photovoltaics, K.-Zuse-Str. 14, D-99099 Erfurt, Germany

Abstract
In recent years, spins of confined carriers in quantum dots are promising candidates for the logical units in quantum computers. In many concepts developed so far, the individual spin q-bits are being manipulated by magnetic fields, which is difficult to achieve. In the current research the recent developments of spin based quantum computing has been reviewed. Then, Single-hole spin in a molecular quantum dots with less energy and more speed has been electrically manipulated and the results have been compared with the magnetic manipulating of the spin.

Key Words
g-factor; electrical manipulation; spin manipulation; molecular quantum dot; magnetic field; g-tensor

Address
A. Meighan, A. Rostami and K. Abbasian : School of Engineering Emerging-Technologies, University of Tabriz, Tabriz 51666, Iran

Abstract
The significant growth of the Si photovoltaic industry has been so far limited due to the high cost of the Si photovoltaic system. In this regard, the most expensive factors are the intrinsic cost of silicon material and the Si solar cell fabrication processes. Conventional Si solar cells have p-n junctions inside for an efficient extraction of light-generated charge carriers. However, the p-n junction is normally formed through very expensive processes requiring very high temperature (~1000\'C). Therefore, several systems are currently under study to form heterojunctions at low temperatures. Among them, carbon nanotube (CNT)/Si hybrid solar cells are very promising, with power conversion efficiency up to 15%. In these cells, the p-type Si layer is replaced by a semitransparent CNT film deposited at room temperature on the n-doped Si wafer, thus giving rise to an overall reduction of the total Si thickness and to the fabrication of a device with cheaper methods at low temperatures. In particular, the CNT film coating the Si wafer acts as a conductive electrode for charge carrier collection and establishes a built-in voltage for separating photocarriers. Moreover, due to the CNT film optical semitransparency, most of the incoming light is absorbed in Si; thus the efficiency of the CNT/Si device is in principle comparable to that of a conventional Si one. In this paper an overview of several factors at the basis of this device operation and of the suggested improvements to its architecture is given. In addition, still open physical/technological issues are also addressed.

Key Words
carbon nanotubes; hybrid carbon nanotube/Si heterojunctions; solar cells; photovoltaics

Address
Paola Castrucci : Department of Physics, University of Roma Tor Vergata, 00133 Roma, Italy

Abstract
This article shows the coarsening behavior of nanoparticle multilayers during heat treatments which produce larger metallic nanostructures with varying shapes and sizes on glass slides. Nanoparticle multilayer films are initially constructed via the layer-by-layer self-assembly of small and monodispersed gold and/or palladium nanoparticles with different compositions (gold only, palladium only, or both gold and palladium) and assembly orders (compounding layers of gold layers over palladium layers or vice versa). Upon heating the slides at 600\'C, the surface nanoparticles undergo coalescence becoming larger nanostructured metallic films. UV-Vis results show a clear reliance of the layering sequence on the optical properties of these metal films, which demonstrates an importance of the outmost (top) layers in each nanoparticle multilayer films. Topographic surface features show that the heat treatments of nanoparticle multilayer films result in the nucleation of nanoparticles and the formation of metallic cluster structures. The results confirm that different composition and layering sequence of nanoparticle multilayer films clearly affect the coalescence behavior of nanoparticles during heat treatments.

Key Words
coarsening; nanoparticles; gold; palladium; nanostructures; optical microscopy

Address
Young-Seok Shon, Dayeon Judy Shon, Van Truong, Diego J. Gavia : Department of Chemistry and Biochemistry, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, USA
Raul Torrico and Yohannes Abate : Department of Physics and Astronomy, California State University Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840, USA

Abstract
We have obtained opal-like photonic crystals based on opals and inverted opals exhibiting a shift of the selective reflection band toward longer and shorter wavelengths with respect to the diffraction band of the initial opal consisting of SiO2 spheres. The contribution of frames forming three-dimensional periodic structures and that of fillers to the spectral arrangement of the diffraction bands has been determined.

Key Words
opal; inverted opal; polymer ED-20; reflectance spectra

Address
Vladimir M. Masalov, Pavel V. Dolganov, Nadezhda S. Sukhinina, Vladimir K. Dolganov and Gennadi A. Emelchenko: Institute of Solid State Physics RAS 143432 Chernogolovka, Moscow District, Russia


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