bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Temperature Elastic Softening due to Vacancies in Boron-Doped FZ Silicon Crystals
Authors: Yamada-Kaneta Hiroshi , Watanabe Hajime , Nagai Yuta , Baba Shotaro , Akatsu Mitsuhiro , Nemoto Yuichi , Goto Terutaka
Published: October 2009

We confirm the following findings obtained in our previous experiment for the low-temperature elastic softening by the vacancies in boron-doped silicon crystals: (1) the steep softening that suddenly starts at 2-4 K in the cooling process, and (2) the complete disappearance of the softening by a weak magnetic field of 4 T applied along [111] direction. We further investigate in detail how the low-temperature softening at a fixed temperature responds to the applied magnetic field, to find the following characteristic anisotropy: The manner of disappearance of the softening strongly depends on the direction of the magnetic field. For the magnetic field imposed along [1-10] direction, nearly 60 % of the full softening still remains even at a strong magnetic field of 8 T, in contrast to the case of magnetic field applied along [111] direction.
Vacancies and Self-Interstitials Dynamics in Silicon Wafers
Authors: Caha O. , Kuběna J. , Kuběna A. , Meduňa M.
Published: October 2009

Successful theoretical models of vacancies, self-interstitials and oxygen dynamics during an ingot growth lead us to apply these models results also to silicon wafers. The modern silicon technology uses successfully the RTA (rapid thermal annealing) in order to form MDZ (magic denude zone) in individual CZ Si wafers. The effect of RTA is based on the utilization of vacancies for control of oxygen precipitation. The question about the theory of kinetics of vacancies and interstitials, which describes its behavior within RTA, is still opened up to now. This work deals mainly with the nucleation of vacancies during RTA concerning various cooling rates and initial states.
Radiation Defects in Silicon: Effect of Contamination by Platinum Atoms
Authors: Hazdra Pavel , Komarnitskyy Volodymyr V.
Published: October 2009

The influence of platinum contamination on the stability of radiation defects produced by
high-energy proton irradiation was investigated in the low-doped n-type float-zone oxygen rich
silicon forming the base of power p+nn+ diodes. Platinum was first implanted and then in-diffused
at different temperatures to obtain different levels of contamination. Diodes were then implanted
with 1.8 MeV protons to a fluence of 2x1010 cm-2 and radiation defect reaction during isochronal
annealing were investigated by deep-level transient spectroscopy. Results show that contamination
of silicon by platinum atoms influences significantly both the introduction rates and the temperature
stability of dominant radiation defects (vacancy-oxygen pairs, divacancies and VOH complexes).
The Effect of Germanium Doping on the Production of Carbon–Related Defects in Electron-Irradiated Czochralski Silicon
Authors: Londos Charalamos A. , Andrianakis A. , Aliprantis D. , Sgourou Efstratia N. , Emtsev Valentin V. , Ohyama H.
Published: October 2009

We present infrared (IR) spectroscopy measurements on carbon-rich, germanium-doped Czochralski-grown (Cz-Si) subjected to irradiation with 2 MeV electrons. The study is focused on the effect of germanium doping on the production of carbon-related defects CiCs, CiOi and CiOi(SiI). For carbon concentrations [Cs] up to 11017 cm-3 the production of the defects increases with the increase of Ge content, for [Ge] up to 11020 cm-3. However, for carbon concentrations around 21017 cm-3 the production of these defects shows a decrease for samples with [Ge]=21020 cm-3 in comparison with those of [Ge]=21019 cm-3. The results are discussed taking into account the effect of germanium on the annihilation of vacancies and self-interstitials in the course of irradiations. In the first case, due to the temporary trapping of vacancies by Ge atoms in the course of irradiation, more self-interstitials are available for the production of carbon interstitials (Cs+ SiI Ci), leading finally to an increase of the carbon-related defects. In the second case, and for [Ge] of the order of ~1020 cm-3 or higher, Ge atoms tend to form large clusters. These clusters attract primary defects facilitating their annihilation on them. As a result, the availability of self-interstitials decreases, which finally leads to a decrease of the carbon-related defects.
Numerical Analysis of mc-Si Crystal Growth
Authors: Kakimoto Koichi , Matsuo Hitoshi , Hisamatsu Syo , Ganesh Birava , Gao Bing , Chen X.J. , Liu Li Jun , Miyazawa Hiroaki , Kangawa Yoshihiro
Published: October 2009

The content and uniformity of impurities and precipitates have an important role in the efficiency of solar cells made of multicrystalline silicon. We developed a transient global model of heat and mass transfer for directional solidification for multicrystalline silicon and a dynamic model of SiC particles and silicon nitride precipitation in molten silicon based phase diagrams. Computations were carried out to clarify the distributions of carbon, nitrogen and oxygen based on segregation and the particle formation in molten silicon during a directional solidification process. It was shown that the content of SiC precipitated in solidified ingots increases as a function of the fraction solidified. It was also clarified from the results that Si2N2O was first formed near the melt-crystal interface, since oxygen concentration in the melt decreases and nitrogen concentration in the melt increases with solidification of the molten silicon. Si3N4 was formed after Si2N2O had been formed.
Molecular Simulation on Interfacial Structure and Gettering Efficiency of Si (110)/(100) Directly Bonded Hybrid Crystal Orientation Substrates
Authors: Kariyazaki Hiroaki , Aoki Tatsuhiko , Izunome Kouji , Sueoka Koji
Published: October 2009

Hybrid crystal orientation technology (HOT) substrates comprised of Si (100) and (110) surface orientation paralleling each <110> direction attract considerable attentions as one of the promising technology for high performance bulk CMOS technology. Although HOT substrates are fabricated by wafer bonding of Si (110) and Si (100) surfaces, it is not clear the atomic configuration of interfacial structure. Furthermore, the possibility for the interface to be an effective gettering source of impurity metals was not well studied. In this paper, we studied the interfacial structure and gettering efficiency of the atomic bonded interface by molecular simulations. The results indicate that the simulated atomic configuration and gettering efficiency of the bonded interface agreed well with the experimental results.
Simulation of XBIC Contrast of Precipitates in Si
Authors: Yakimov Eugene B.
Published: October 2009

Simulation of contrast for small spherical defects in the X-ray beam-induced current (XBIC) mode has been carried out. Under simulations the excess carrier generation function is described by the rigid cylinder with the constant generation rate inside it. The dependence of maximum contrast value on the precipitate depth, diffusion length and effective beam radius is calculated. The XBIC contrast profile as a function of diffusion length, of beam radius and of precipitate depth has been calculated that allows to evaluate the spatial resolution of the technique. The results obtained are compared with those calculated for the EBIC contrast of the same defect. It is shown that in the semiconductor materials with the small diffusion length the XBIC contrast could be comparable with the EBIC one.
Dislocation Nucleation in Heteroepitaxial Semiconducting Films
Authors: Pichaud Bernard , Burle N. , Texier Michael , Fontaine C. , Vdovin V.I.
Published: October 2009

The nucleation of dislocation in semiconductors is still a matter of debate and especially in heteroepitaxial films. To understand this nucleation process the classical models of dislocation nucleation are presented and discussed. Two main points are then developed: emission of dislocations from surface steps and the role of point defects agglomeration on dislocation nucleation. Recent atomic simulation of half loops emission from surface steps and experimental evidences of anisotropic relaxation of GaInAs films deposited on vicinal (111) GaAs substrates strongly support surface steps as preferential sites for nucleation. In low temperature buffer layer structures (SiGe/Si) an original dislocation structure is observed which corresponds to the dislocation emission in different glide systems by a unique nucleation centre.
Impurity Engineering of Czochralski Silicon
Authors: Chen Jia He , Ma Xiang Yang , Yang De Ren
Published: October 2009

The novel concept of “impurity engineering in CZochralski (CZ) silicon ” for large scaled integrated circuits has been reviewed. By doping with a certain impurities into CZ silicon materials intentionally, such as nitrogen (N), germanium (Ge) and even carbon (C, with high concentration), internal gettering ability of CZ silicon wafers could be improved. Meanwhile, void defects in CZ silicon wafer could be easily eliminated during annealing at higher temperatures. Furthermore, it was also found that the mechanical strength could be increased, so that breakage of wafers decreased. Thus, it is believed that by impurity engineering CZ silicon wafers can satisfy the requirment of ultra large scale integrated circuits.
The Role of the Interstitial Oxygen in the Recovery and Evolution of the Boron Implantation Damage
Authors: Mica Isabella , Polignano Maria Luisa , Cazzaniga F. , Di Piazza L. , Mariani M. , Ricci E. , Sammiceli F. , Speranza S.
Published: October 2009

The recovery of the boron implantation damage can be very difficult. Depending on the energy and the dose many dislocations are generated at the projected range of the boron implantation. The morphology of these dislocations depends on the silicon substrate. In this work we demonstrate that the interstitial oxygen concentration ([Oi]) is related with the dislocation dimension, density end morphology. Particularly long dislocation dipoles were generated by the boron implantation in substrate with interstitial oxygen, and their density is connected with the [Oi] concentration.
Study of the Mechanisms of Oxygen Precipitation in RTA Annealed Cz-Si Wafers
Authors: Litovchenko V.G. , Lisovskyy I.P. , Voitovych M. , Sarikov Andrey V. , Zlobin S.O. , Kladko V.P. , Machulin V.
Published: October 2009

In this paper, the influence of the rapid thermal annealing of single crystalline Cz-Si wafers on the evolution of the concentration of interstitial oxygen as well as oxygen in precipitated oxide phase was investigated by infrared spectroscopy. The wafers were preliminary furnace annealed to create the precipitate seeds. The concentration of interstitial oxygen was shows to decrease considerably as a result of annealing during up to 40 min together with the growth of the concentration of precipitated oxygen. This effect depended on the purity and defect structure of initial wafers. The kinetic model was developed to account for the observed effects based on the modification of the solubility level for interstitial oxygen induced by defects as well as its diffusivity. Obtained results of simulation agree well with the experimental data.
Electronic States of Oxygen-Free Dislocation Networks Produced by Direct Bonding of Silicon Wafers
Authors: Trushin Maxim , Vyvenko O.F. , Mchedlidze Teimuraz , Kononchuk Oleg , Kittler Martin
Published: October 2009

The results of experimental investigations of the dislocation-related DLTS-peaks originated from the dislocation networks (DN) are presented. Samples with DNs were produced by direct bonding of p-type silicon wafers and no enhancement of oxygen concentration was detected near the DN plane. Origins of the DLTS peaks were proposed and a correlation with the dislocation-related photoluminescence data was established based on known dislocation structure of the samples. Two types of shallow DLTS peaks exhibited Pool-Frenkel effect, which could be linked to the dislocation deformation potential. One of the shallow DLTS peaks was related to straight parts of screw dislocations and another - to the intersections of the dislocations.
Role of Ion Irradiation Induced Lattice Defects on Nanoscale Capacitive Behavior of Graphene
Authors: Sonde Sushant , Giannazzo Filippo , Raineri Vito , di Franco Salvatore , Marino Antonio , Rimini Emanuele
Published: October 2009

Irradiation with high energy (500 keV) C+ ions at fluences from 11013 to 11014 cm-2 was used to introduce controlled amounts of defects in single layers of graphene deposited on a SiO2(100 nm)/n+Si substrate. Scanning Capacitance Spectroscopy (SCS) was used as non-destructive characterization technique to probe the effect of irradiation on the electrical properties of graphene. In particular, a comparative study between the local capacitance of pristine graphene and irradiated graphene is presented, showing that lateral variations in irradiated graphene are distinctly higher. The local quantum capacitance per unit area C’q of graphene was extracted from raw data. While a narrow distribution of C’q values was obtained in pristine graphene, two distinct distributions were obtained in irradiated monolayers, associated to locally damaged and not damaged regions, respectively.
Boron and Phosphorus Implantation Induced Electrically Active Defects in p-Type Silicon
Authors: Senawiratne Jayantha , Cites Jeffery S. , Couillard James G. , Moll Johannes , Kosik Williams Carlo A. , Whiting Patrick G.
Published: October 2009

Electrically active defects induced by ion implantation of boron and phosphorus into silicon and their recovery under isothermal annealing at 450 °C were investigated using Deep Level Transient Spectroscopy (DLTS) and Energy Resolved Tunneling Photoconductivity (ERTP) spectroscopy at cryogenic temperatures. DLTS results show electrically active deep traps located at Ev+0.35 eV and Ev+0.53 eV in boron implanted Si and at Ev+0.34 eV, Ev+0.43 eV, and Ev+0.38 eV in phosphorus implanted Si. These meta-stable defect sites were found to be either eliminated or significantly reduced in thermally annealed samples. We assigned these defect sites to hydrogen and carbon incorporated complexes formed during ion implantation. Corroborating the DLTS results, the photocurrent measurement also revealed a strong reduction of electrically active defects states, extended from EC – 0.3 eV up to the conduction band edge of Si, upon isothermal annealing.
Influence of Hydrogen on the Structural Stability of Annealed Ultrathin Si/Ge Amorphous Layers
Authors: Frigeri Cesare , Nasi L. , Serényi M. , Csik A. , Erdélyi Z. , Beke Dezső L.
Published: October 2009

The influence of hydrogen on the structural stability of multilayers made of ultrathin
(3 nm) Si and Ge amorphous layers submitted to annealing to activate Si and Ge intermixing has
been studied by TEM and AFM. By energy dispersive microanalysis the interdiffusion of Si and
Ge has been observed. The Si/Ge multilayers, however, underwent remarkable structural
degradation because of the formation of hydrogen bubbles which give rise to surface bumps and
eventually craters when the bubbles blow up because of too high internal pressure in samples
with high H content and annealed at high temperatures. The hydrogen forming the bubbles comes
from the rupture of the Si-H and Ge-H bonds activated by the thermal energy of the annealing
and by the energy released by the recombination of thermally generated electron hole pairs.
Demonstration of Defect-Induced Limitations on the Properties of Au/3C-SiC Schottky Barrier Diodes
Authors: Eriksson Jens , Weng Ming Hung , Roccaforte Fabrizio , Giannazzo Filippo , Leone Stefano , Raineri Vito
Published: October 2009

The electrical current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/3C-SiC Schottky diodes were studied as a function of contact area. The results were correlated to defects in the 3C-SiC, which were studied and quantified by conductive atomic force microscopy (C-AFM). A method based on C-AFM was introduced that enables current-voltage characterization of diodes of contact radius down to 5 µm, which consequently allows the extraction of diode parameters for Schottky diodes of very small contact area.
Hydrogenation in Crystalline Silicon Materials for Photovoltaic Application
Authors: Hahn Giso , Käs Martin , Herzog Bernhard
Published: October 2009

In this contribution an overview of hydrogenation issues for (multi-)crystalline silicon
material is given. Crystalline silicon material for photovoltaic application contains more defects
than material used for other semiconductor device fabrication. Therefore passivation of bulk defects
has to be performed to reach higher efficiencies and exploit the cost reduction potential of these
materials. Especially minority charge carrier lifetimes of ribbon silicon can be drastically improved
by hydrogenation in combination with a gettering step. Apart from bulk passivation atomic
hydrogen plays an important role in surface passivation via dielectric layers. Performance of single
dielectric layers or stack systems can be increased after a hydrogenation step. It is believed that
hydrogen can passivate defects at the silicon/dielectric interface allowing for lower surface
recombination velocities. In industrial application hydrogenation is performed via deposition of a
hydrogen-rich PECVD SiNx layer followed by a belt furnace annealing step. Surface passivation for
characterization of charge carrier bulk lifetime is often performed with the same technique, omitting
the annealing step to avoid in-diffusion of hydrogen. It is shown that for some crystalline silicon
materials even the PECVD SiNx deposition alone (without annealing step) can cause significant
bulk defect passivation, which in this case causes an unwanted change of bulk lifetime.
Passivation of Si Surfaces Investigated by In Situ Photoluminescence Techniques
Authors: Rappich J. , Zhang X. , Rosu D.M. , Schade U. , Hinrichs K.
Published: October 2009

We investigated Si surfaces modified by wet-chemical and electrochemical treatments using pulsed photoluminescence (PL) and infrared spectroscopic ellipsometry during and after processing, both also in surface mapping techniques. Etching of oxidized Si surfaces by HF containing solutions lead to an enhancement in PL due to hydrogenation of the surface what improves the surface passivation and reduces the recombination loss of charge carriers via surface/interface states. PL measurements show that the H-terminated surface is attacked soon by HF or H2O species increasing again the recombination loss. Hence, a narrow time window for this type of processing exists. Nitrogen purging or exchanging the etching solution by a non-etching solution under negative bias decelerated the defect formation in HF solutions. Grafting of organic molecules (exchanging the H-Si by a C-Si bond) induces only small amounts of defects at the interface but stabilizes PL on a high level (i.e. surface recombination is low) for much longer times than for H-terminated Si surfaces.
Gettering Efficiency of Si (110)/(100) Directly Bonded Hybrid Crystal Orientation Substrates
Authors: Aoki Tatsuhiko , Kariyazaki Hiroaki , Sueoka Koji , Izunome Kouji
Published: October 2009

We have investigated the gettering efficiency at the interface of Si (110) and Si (100)
directly bonded (DSB) substrates. DSB substrates were prepared by conventional bonding and
grinding back methods. DSB substrates were intentionally contaminated with 3d transition metals (Fe,
Ni, Cu) and then annealed at 1000 oC. The dependence of metal concentrations on the depth was
evaluated by a secondary ionization mass spectrometer (SIMS). Furthermore, we observed the
interface of DSB by transmission electron microscope (TEM), and characterized the form of the
gettered metals.
Trans-RP Gettering and Out-Diffusion of Oxygen Implanted into Highly B-Doped Silicon
Authors: Kögler Reinhard , Dubois Christiane , Gerlach Jürgen W. , Hutter H. , Mücklich A. , Skorupa Wolfgang
Published: October 2009

Implantation of 18O into highly B-doped and undoped silicon provides the possibility to investigate the effect of B-doping and to distinguish the processes of in-diffusion and out-diffusion of oxygen by profiling of 16O and 18O, respectively. The simultaneous in- and outdiffusion of oxygen was observed at 1000°C under oxidizing conditions. For silicon, heavily Bdoped to concentrations of 1019 B cm-3, oxygen tends to diffuse out toward the surface. Moreover, a fraction of the oxygen from both sources, implanted 18O and in-diffused 16O, also migrates deep into the substrate and is trapped far beyond the mean ion range RP in the depth of x 3RP at the so-called trans-RP gettering peak. In undoped silicon oxygen accumulation only takes place at vacancy-type defects introduced by ion implantation at a position shallower than RP. The mobility of oxygen implanted into B-doped Si is higher than for implantation into undoped Si. Highly mobile defects are suggested to be formed in B-doped silicon beside the common mobile interstitial oxygen, Oi, and the immobile SiOX precipitates. These I OXBY defects may involve selfinterstitials, I, and O and B atoms. The trans-RP peak appears due to the decay of these defects and the segregation of their constituents.
Iron Gettering in CZ Silicon during the Industrial Solar Cell Process
Authors: Laades Abdelazize , Lauer K. , Maier C. , Alber D. , Bähr M. , Nutsch J. , Lossen J. , Lawerenz A.
Published: October 2009

We investigated the impact of using low quality feedstock such as recycled
silicon and simplified pulling condition on the performance of CZ silicon solar cells. Groups
of wafers carefully chosen from different ingots were analyzed after different solar cell
process steps by minority carrier lifetime measurements, by measurements of the interstitial
iron content and by measurements of the total impurity content using NAA. Our results show
that the main electronic properties of the ingots, namely the carrier lifetime, interstitial iron
content and base resistivity are strongly affected by feedstock quality. Surprisingly, high solar
cell efficiencies were achieved using highly contaminated silicon. These positive results are
due to the beneficial effect of impurity segregation gettering by phosphorous diffusion and
aluminum alloying. Post-diffusion gettering by an additional annealing step was demonstrated
to enhance the charge carrier lifetime.
Effect of Oxygen in Low Temperature Boron and Phosphorus Diffusion Gettering of Iron in Czochralski-Grown Silicon
Authors: Vähänissi Ville , Haarahiltunen Antti , Talvitie H. , Asghar M.I. , Yli-Koski Marko , Savin Hele
Published: October 2009

Low temperature boron and phosphorous diffusion gettering (BDG and PDG) of iron in Czochralski-grown silicon were experimentally studied. Differences and similarities between the gettering techniques were clarified by using intentionally iron contaminated wafers emphasizing especially the effect of oxygen. Experiments showed that the surprisingly high gettering effects of BDG could be explained by B-Si precipitates. Oxygen precipitation was seen to decrease minority carrier diffusion length after long gettering at low temperatures in both BDG and PDG. In the case of BDG oxygen precipitation affected more as a higher thermal budget was needed to obtain similar sheet resistance to that of PDG. According to experiments the efficiency of BDG can not be concluded from the sheet resistance, whereas the efficiency of PDG can. This has practical influences in a process control environment.
Far-Action Defects Formation and Gettering in 6H-SiC Lely Crystals Irradiated by Bi
Authors: Shustov D.B. , Kolesnikova E.V. , Kalinina Evgenia V. , Skuratov V.A. , Zamoryanskaya M.V.
Published: October 2009

Defects distribution in 6H-SiC implanted with Bi ions was investigated with the local cathodoluminescence. There are two typical areas with radiation defects found in implanted samples. Implanted layer was about 27 micrometers depth. Far-action area with radiation defects was observed for the first time. Thickness of this area varies from few tens up to hundreds micrometers. This effect depended on concentration of defects i.e. irradiation fluence. Radiation defects at this area disappeared after annealing the sample if fluence is not to high.
Quantitative Iron Concentration Imaging
Authors: Schubert Martin C. , Habenicht Holger , Kerler Michael J. , Warta Wilhelm
Published: October 2009

Iron concentration imaging has been proven to be a very valuable analysis technique for silicon material characterization. We applied this method to determine the influence of a low temperature annealing after surface passivation on the interstitial iron concentration. The influence of hydrogen passivation induced by silicon nitride passivation is estimated by comparison of silicon nitride and aluminum oxide passivation. The second part of this work deals with systematic errors inherent to the iron concentration technique. Simulations show under which conditions errors occur due to the non-uniformity of carrier profiles.
EBIC Investigation of the Influence of Hydrogen Passivation on Thin-Film Polycrystalline Silicon Solar Cells Obtained by Aluminium Induced Crystallization and Epitaxy
Authors: Van Gestel Dries , Gordon Ivan , Poortmans Jef
Published: October 2009

The relatively new “thin-film polycrystalline-silicon (pc-Si) (grain size of 0.1-100 µm) solar cell on foreign substrate” technology aims at low-cost devices with energy conversion efficiencies above 12 %. A very promising technique to obtain thin pc-Si layers is aluminum-induced crystallization (AIC). Solar cell absorber layers can be made by epitaxial thickening of these AIC seed layers. So far, we have reached energy conversion efficiencies of up to 8% with this approach. In contrast to what is expected a performance independent of the grain size is found which is explained by the presence of intragrain defects. In this paper the electrical activity of both the intragrain defects as well as the grain boundaries is investigated with electron beam induced current (EBIC) measurements before and after hydrogen plasma passivation. Metal-insulator-semiconductor contacts were used as collecting junction to eliminate the interference of the junction shape with the EBIC measurement as found when diffused emitters where used. It is shown that both grain boundaries and intragrain defects are electrically active before and after hydrogen plasma passivation. Finally we argue that Leff,mono, the diffusion length inside the grains, is probably much closer to 1µm in our layers than equal to 100µm as often expected in the literature.
Electron-Beam-Induced Current Study of Breakdown Behavior of High-K Gate MOSFETs
Authors: Chen Jun , Sekiguchi Takashi , Takase Masami , Fukata Naoki , Hasunuma Ryu , Yamabe Kikuo , Sato Motoyuki , Yamada Keisaku , Chikyo Toyohiro
Published: October 2009

We report a dynamic and microscopic investigation of electrical stress induced defects in metal-oxide-semiconductor (MOS) devices with high-k gate dielectric by using electron-beam induced current (EBIC) technique. The correlation between time-dependent dielectric breakdown (TDDB) characteristics and EBIC imaging of breakdown sites are found. A systematic study was performed on pre-existing and electrical stress induced defects. Stress-induced defects are related to the formation of electron trapping defects. The origin of pre-existing defects is also discussed in terms of oxygen vacancy model with comparing different gate electrodes.
SEM Characterization of Silicon Layers Grown on Carbon Foil
Authors: Brantov Sergei K. , Eltzov A.V. , Feklisova Olga V. , Yakimov Eugene B.
Published: October 2009

Characterization of defect structure in silicon ribbon grown on carbon foil has been carried out. The structure of grown Si layers and a dislocation density in these layers have been studied using selective chemical etching and the Electron Backscattering Diffraction. It is observed that the layers consist of rather large grains, the majority of which is elongated along the growth direction with a similar surface orientation and with a misorientation angle between neighboring grains of 60º. This means that such grains are separated by the (111) twin boundaries. The dislocation density in different grains is found to vary from 102 to 107cm-2. The energy dispersive X-Ray microanalysis has shown that some twin boundaries are enriched with carbon.
Anisotropic Strain – Anisotropic Heating Engineering for Silicon Nanocrystals in SiO2
Authors: Antonova I.V. , Marin D.V. , Volodin Vladimir A. , Skuratov V.A. , Jedrzejewski J. , Balberg I.
Published: October 2009

In the present paper we discuss effects due to high-energy ion bombardment of SiO2 layers with embedded Si nanocrystals (NCs), such as the formation of new Si NCs in such layers, amorphization of previously existing NCs, modification of NC size distribution, and modification of optical and electrical properties of NCs. These effects are identified as resulting from anisotropic strain - anisotropic heating in NCs-SiO2 layers under ion irradiation.
Dependence of Luminescence Properties of Bonded Si Wafers on Surface Orientation and Twist Angle.
Authors: Steinman E.A. , Kononchuk Oleg , Tereshchenko A.N. , Mazilkin A.A.
Published: October 2009

PL spectra of SOI wafers with buried oxide (BOX) layer were measured after dissolution
annealing at 1200°. Depending on mutual orientation of starting base and top wafers different
patterns of luminescence bands were observed after annealing. While the small fraction of
luminescence clearly originated from dislocation related centers, another intensive band appeared in
the range 0.8 – 0.95eV with certain dependence of maximum position on the twist misorientation.
TEM investigation confirmed the existence of dislocation net at the interface. On the other hand
some peculiarities of PL spectra did not support their relation to dislocations. Though a stepped
chemical etch of surface layer confirmed the origin of new band being at the interface too.
Therefore a nature of possible defects generated due to dissolution of BOX layer is discussed.
D-Line Emission from Small Angle Grain Boundaries in Multicrystalline Si
Authors: Sekiguchi Takashi , Lee Woong , Chen Jun , Chen Bin
Published: October 2009

We have characterized optical property of small-angle (SA) grain-boundaries (GBs) in high-pure multicrystalline Si by using cathodoluminescence (CL). Prior to CL measurement, the electrical activity of GBs were evaluated by using electron-beam-induced current (EBIC). The SA-GBs are categorized into two groups with room temperature (RT-) EBIC contrast. The SA-GBs with misorientation angle about 1º give weak RT-EBIC contrast and yield D3 and D4. The SA-GBs with 2.5º show strong EBIC contrast and yield D1 and D2. These correspondences reflect the dislocation density at the SA-GBs. We also found the curious distribution of D1 emission in some special GBs, which is now difficult to explain. It is noticed that large-angle GBs do not show any D-line emissions at all.
Optimization of the Luminescence Properties of Silicon Diodes Produced by Implantation and Annealing
Authors: Arguirov Tzanimir , Mchedlidze Teimuraz , Reiche Manfred , Kittler Martin
Published: October 2009

Incorporation of optical components into microelectronic devices will significantly improve their performance. Absence of effective Si-based light emitter hampers such integration. In the present work light emitting Si diodes, fabricated by dopant (boron or phosphorous) implantation and annealing are investigated. Different implantation doses and annealing temperatures were employed. The efficiency of the electroluminescence (EL), obtained from such structures was measured and correlated with the fabrication process parameters. As previously reported, the EL of band-to-band radiative transition in Si is strongly influenced, by the dopant implantation dose, i.e. higher doses usually enhance EL. Our results suggest that the effect is mainly related to the increase of minority carrier lifetime in the substrate. Distinct measurements showed that the higher implantation doses lead longer carrier lifetimes in the samples. The correlation between lifetime and the EL efficiency could be satisfactory explained in the frame of a classical model, considering the carrier-injection dependence of the rates of the three main recombination mechanisms in silicon, i.e. multi-phonon, radiative and Auger recombination. We suppose that the increase in the implantation dose improves minority carrier lifetime due to the gettering of impurity atoms from the substrate material to the highly doped emitter region.
Novel Trends in SOI Technology for CMOS Applications
Authors: Kononchuk Oleg , Landru Didier , Veytizou Christelle
Published: October 2009

High temperature annealing of SOI wafers in non-oxidized ambient leads to internal
Buried Oxide (BOX) dissolution. The underlying mechanisms and kinetics of this effect are
discussed. High quality SOI wafers with very thin BOX down to 2nm are demonstrated utilizing
optimized annealing conditions. Hybrid SOI/bulk wafers are obtained by the new process applying
silicon nitride mask on the wafer surface. Stability of SOI and Si3N4/SOI systems at high
temperatures is discussed and optimized process window is determined.
Buried Insulating Layer Formation in Cz Si Wafers after Helium Implantation, Nitrogen Plasma Treatment and Annealing
Authors: Frantskevich N.V. , Frantskevich A.V. , Fedotov A.K. , Mazanik A.V.
Published: October 2009

Standard p-type 12 cm Cz Si wafers were implanted by helium ions. The implanted and nonimplanted samples were subsequently subjected to nitrogen plasma treatment and final vacuum annealing. SEM studies have shown the absence of large-scale defects on the top wafer surface and the presence of a layer revealing contrast with surrounding silicon on the cleavage surface at a depth corresponding to the projected range Rp. Scanning over a crater formed by ion sputtering has exposed no defects to the depth of Rp and beyond. At the same time, at a depth of Rp there is a layer with the morphology (structure) significantly different from the surrounding defect-free areas. The measurements of transverse conductivity have shown that the wafer with the formed nitrogen-contained layer possesses dielectric properties with a breakdown voltage up to 15 V.
Primitive Sca-1 Positive Bone Marrow HSC in Mouse Model of Aplastic Anemia: A Comparative Study through Flowcytometric Analysis and Scanning Electron Microscopy
Authors: Chatterjee Sumanta , Basak Pratima , Das Prosun , Das Madhurima , Pereira Jacintha Archana , Dutta Ranjan Kumar , Chaklader Malay , Chaudhuri Samaresh , Law Sujata
Published: October 2009

Self-renewing Hematopoietic Stem Cells (HSCs) are responsible for reconstitution of all blood cell lineages. Sca-1 is the “stem cell antigen” marker used to identify the primitive murine HSC population, the expression of which decreases upon differentiation to other mature cell types.Sca-1+HSCs maintain the bone marrow stem cell pool throughout the life. Aplastic anemia is a disease considered to involve primary stem cell deficiency and is characterized by severe pancytopenia and a decline in healthy blood cell generation system. Studies conducted in our laboratory revealed that the primitiveSca-1+BM-HSCs (bone marrow hematopoietic stem cell) are significantly affected in experimental Aplastic animals pretreated with chemotherapeutic drugs (Busulfan and Cyclophosphamide) and there is increased Caspase-3 activity with consecutive high Annexin-V positivity leading to premature apoptosis in the bone marrow hematopoietic stem cell population in Aplastic condition. TheSca-1bright, that is, “more primitive” BM-HSC population was more affected than the “less primitive” BM-HSCSca-1dim⁡population. The decreased cell population and the receptor expression were directly associated with an empty and deranged marrow microenvironment, which is evident from scanning electron microscopy (SEM). The above experimental evidences hint toward the manipulation of receptor expression for the benefit of cytotherapy by primitive stem cell population in Aplastic anemia cases.
Tissue-Derived Stem and Progenitor Cells
Authors: Tesche Leora J. , Gerber David A.
Published: October 2009

The characterization and isolation of various stem cell populations, from embryonic through tissue-derived stem cells, have led a rapid growth in the field of stem cell research. These research efforts have often been interrelated as to the markers that identify a select cell population are frequently analyzed to determine their expression in cells of distinct organs/tissues. In this review, we will expand the current state of research involving select tissue-derived stem cell populations including the liver, central nervous system, and cardiac tissues as examples of the success and challenges in this field of research. Lastly, the challenges of clinical therapies will be discussed as it applies to these unique cell populations.
Efficient Functionalisation of Cubic Monovinylsilsesquioxanes via Cross‐Metathesis and Silylative Coupling with Olefins in the Presence of Ruthenium Complexes
Authors: Żak Patrycja , Pietraszuk Cezary , Marciniec Bogdan , Spólnik Grzegorz , Danikiewicz Witold
Published: October 2009

Monovinylheptaisobutylsilsesquioxane undergoes efficient cross‐metathesis and silylative coupling with styrenes. Allyl derivatives were successfully tested in cross‐metathesis in the presence of first generation Grubbs’ catalyst, while heteroatom‐substituted vinyl derivatives (vinyl ethers, 9‐vinylcarbazole) efficiently undergo silylative coupling catalysed by ruthenium hydride complexes. Both reactions proceed highly stereoselectively and lead to nearly quantitative formation of E isomers. Only when vinyl ethers are used does the reaction lead to a mixture of stereoisomers. Atmospheric pressure photoionisation has been successfully used for recording mass spectra of the functionalised silsesquioxanes.
Reusable Copper‐Aluminum Hydrotalcite/rac‐BINOL System for Room Temperature Selective Aerobic Oxidation of Alcohols
Authors: Kantam M. Lakshmi , Arundhathi R. , Likhar Pravin R. , Damodara D.
Published: October 2009

An efficient catalyst system consisting of copper‐aluminum hydrotalcite/rac‐BINOL ligand has been developed for the oxidation of alcohols using air as a green oxidant at room temperature. Various alcohols could be transformed into their corresponding aldehydes or ketones in good to excellent yields using the set of optimal conditions. This composite catalytic system can also be recovered and reused for several cycles without a significant loss of catalytic activity.
Metal‐Free: An Efficient and Selective Catalytic Aerobic Oxidation of Hydrocarbons with Oxime and N‐Hydroxyphthalimide
Authors: Zheng Gengxiu , Liu Chunhong , Wang Qiufen , Wang Mingyu , Yang Guanyu
Published: October 2009

A non‐metal catalytic system consisting of dimethylglyoxime (DMG) and N‐hydroxyphthalimide (NHPI) for the selective oxidation of hydrocarbons with dioxygen is described. The synergistic effect of DMG and NHPI ensures its efficient catalytic ability: 82.1% conversion of ethylbenzene with 94.9% selectivity for acetophenone could be obtained at 80 °C under 0.3 MPa of dioxygen in 10 h. Several hydrocarbons were efficiently oxidized to their corresponding oxygenated products under mild conditions.
Axial Chirality Control by 2,4‐Pentanediol for the Alternative Synthesis of C3*‐TunePhos Chiral Diphosphine Ligands and Their Applications in Highly Enantioselective Ruthenium‐Catalyzed Hydrogenation of β‐Keto Esters
Authors: Sun Xianfeng , Li Wei , Hou Guohua , Zhou Le , Zhang Xumu
Published: October 2009

A highly efficient strategy for the synthesis of a series of C3*‐TunePhos chiral diphosphine ligands was well established with several remarkable features. The synthetic utility of these ligands was explored for the ruthenium‐catalyzed asymmetric hydrogenation of β‐keto esters. Up to 99% ee values were achieved for the enantioselective synthesis of β‐hydroxy acid derivatives, which are very important chiral building blocks for the synthesis of a variety of natural products and biologically active molecules.
Alte und neue Konzepte für thermoelektrische Materialien
Authors: Sootsman Joseph R. , Chung Duck Young , Kanatzidis Mercouri G.
Published: October 2009

Grundkonzepte für die Erforschung thermoelektrischer Materialien, der gegenwärtige Kenntnisstand und neueste Entwicklungen auf dem Gebiet sind die Themen dieses Aufsatzes. In aktuellen Forschungsarbeiten werden der Leistungsfaktor maximiert und/oder die Wärmeleitfähigkeit minimiert, um höhere ZT–Werte zu erzielen. Ansätze zur Maximierung des Leistungsfaktors sind die Entwicklung neuer oder das Optimieren existierender Materialien durch Dotieren sowie die Erforschung nanoskaliger Materialien. Die Wärmeleitfähigkeit kann minimiert werden durch das Herstellen fester Lösungen, die Verwendung von Materialien mit niedriger intrinsischer Wärmeleitfähigkeit und durch Nanostrukturierung. Dieser Aufsatz beschreibt die aussichtsreichsten thermoelektrischen Bulkmaterialien unter Berücksichtigung der während des letzten Jahrzehnts gewonnenen Erkenntnisse. Zu Beginn werden die Kristallstruktur und die chemischen und physikalischen Eigenschaften einphasiger Bulkmaterialien sowie die Optimierung ihrer thermoelektrischen Leistung diskutiert. Anschließend wird untersucht, welche neuen Möglichkeiten sich durch den Einsatz nanostrukturierter Kompositmaterialien ergeben. Den Abschluss bildet ein Ausblick in die fernere Zukunft.
Phthalocyanine–C60 Fused Conjugates Exhibiting Molecular Orbital Interactions Depending on the Solvent Polarity
Authors: Fukuda Takamitsu , Hashimoto Naoaki , Araki Yasuyuki , El‐Khouly Mohamed E. , Ito Osamu , Kobayashi Nagao
Published: October 2009

New covalently C60‐connected zinc phthalocyanine (ZnPc) derivatives have been synthesized by utilizing successive cycloaddition reactions of C60 with a ZnPc derivative containing a pyridazine moiety employing Komatsu’s method in reaction of C60 with phthalazine. The UV/Vis absorption spectrum of the fused conjugate (5) shows red shifts from the corresponding absorption of ZnPc derivative (8), indicating interactions between the ZnPc and C60 moieties. The DFT calculations under non‐polar medium predict that the HOMO and LUMO of 5 localize on the ZnPc moiety, whereas LUMO+1 localizes on the C60 moiety, which reasonably explain the magnetic circular dichroism (MCD) and absorption spectra in toluene. Electrochemical redox potentials of 5 in polar solvents indicate the first‐oxidation potential arises from the ZnPc moiety, whereas the first reduction potential is associated with the C60 moiety, suggesting the LUMO localizes on the C60 moiety in polar solvent. This reversal of the LUMO is supported by the ZnPc‐fluorescence quenching with a nearby C60 moiety in benzonitrile, which leads to the charge‐separation via the excited singlet state of the ZnPc moiety. In toluene on the other hand, such a ZnPc‐fluorescence quenching owing to the photoinduced charge separation is not observed as predicted by the DFT‐calculated LUMO on the ZnPc moiety.
The neighbor enclosed area tracking algorithm for extratropical wintertime cyclones
Authors: Inatsu Masaru
Published: October 2009

The neighbor enclosed area tracking (NEAT) algorithm is proposed as an alternative method to conventional point‐to‐point cyclone tracking approaches. NEAT enables us to count the genesis and tracks of individual cyclones as well as the number of merged and separated cyclones. Little difference in cyclone genesis or track climatology in the Northern Hemisphere was found between NEAT and conventional tracking. The NEAT results indicate a high probability of cyclone merger in the western Pacific and western Atlantic. Composite maps and backtracking from merged cyclones reveal the characteristics of merged cyclones. Copyright © 2009 Royal Meteorological Society
Evaluation of high‐resolution precipitation estimate over the Amazon Basin
Authors: Santos e Silva Cláudio Moisés , de Freitas Saulo Ribeiro , Gielow Ralf , de Barros Sheila Santana
Published: October 2009

Using rainfall data from S‐band radar measurements, the estimative of the rainfall from the 3B42_V6 algorithm was evaluated for the region of the Tropical Rainfall Measurement Mission and Large Scale Biosphere–Atmosphere Experiment in Amazonia (TRMM–LBA) experiment, which was conducted in the Amazon Basin during the 1999 rainy season. The algorithm correctly represented the diurnal rainfall cycle, but underestimated overall precipitation rates by about 50%. It adequately represented most of the stratiform (convective) rainfall during the break (active) phase of the South American Monsoon System (SAMS). Thus, some uncertainties, as well as the algorithm applicability for the region and period studied, were demonstrated. Copyright © 2009 Royal Meteorological Society
Quasi‐biennial oscillations in spectral aerosol optical depth
Authors: Beegum S. Naseema , Moorthy K. Krishna , Babu S. Suresh , Reddy R. Ramakrishna , Gopal K. Rama , Ahmed Y. Nazeer
Published: October 2009

Analysis of long‐term time series of monthly mean aerosol optical depths (AOD) at four tropical stations over Asia and Africa revealed the presence of significant annual oscillations (AO) and quasi‐biennial oscillations (QBO). While the AOs were the dominant features, the QBOs in AOD (QBOAOD) were also quite strong and were well associated with the QBO in stratospheric zonal wind (QBOU). At the equatorial stations, QBOAOD were out of phase with QBOU, while they were in phase at the off‐equatorial stations. However, QBO in both outgoing longwave radiation (OLR) and rainfall showed an out‐of‐phase relationship with QBOAOD at all stations. Copyright © 2009 Royal Meteorological Society
Pulsed electromagnetic fields accelerate proliferation and osteogenic gene expression in human bone marrow mesenchymal stem cells during osteogenic differentiation
Authors: Sun Li‐Yi , Hsieh Dean‐Kuo , Lin Po‐Cheng , Chiu Hsien‐Tai , Chiou Tzyy‐Wen
Published: October 2009

Osteogenesis is a complex series of events involving the differentiation of mesenchymal stem cells to generate new bone. In this study, we examined the effect of pulsed electromagnetic fields (PEMFs) on cell proliferation, alkaline phosphatase (ALP) activity, mineralization of the extracellular matrix, and gene expression in bone marrow mesenchymal stem cells (BMMSCs) during osteogenic differentiation. Exposure of BMMSCs to PEMFs increased cell proliferation by 29.6% compared to untreated cells at day 1 of differentiation. Semi‐quantitative RT‐PCR indicated that PEMFs significantly altered temporal expression of osteogenesis‐related genes, including a 2.7‐fold increase in expression of the key osteogenesis regulatory gene cbfa1, compared to untreated controls. In addition, exposure to PEMFs significantly increased ALP expression during the early stages of osteogenesis and substantially enhanced mineralization near the midpoint of osteogenesis. These results suggest that PEMFs enhance early cell proliferation in BMMSC‐mediated osteogenesis, and accelerate the osteogenesis. Bioelectromagnetics 31:209–219, 2010. © 2009 Wiley‐Liss, Inc.