bluuebunny/crossref_metadata_2025 huggingface dataset:
Innovations in Food-Supply Veterinary Medicine: The Michigan State University College of Veterinary Medicine Summer Food Systems Fellowship Program
Authors: Howard Erin K. , Lloyd James W. , Grooms Daniel L.
Published: October 2009

The purpose of this article is to outline a new educational model at Michigan State University's College of Veterinary Medicine. The Summer Food Systems Fellowship Program provides opportunities for food industry-oriented students to experience summer employment with agriculture industry partners, and gives the industry partners exposure to the veterinary profession.
Collaborative, Case-based Learning: How Do Students Actually Learn from Each Other?
Authors: Thurman Joanne , Volet Simone E. , Bolton John R.
Published: October 2009

The value of collaborative, case-based, and problem-based learning has received increased attention in recent years. Several studies have documented veterinary staff and students’ generally positive feedback on group learning activities, but one largely unaddressed question is how students actually learn from each other. This study examined how second-year veterinary students learned from each other during a collaborative, case-based learning project. Data were students’ written reflections on their learning in the veterinary course and the specific learning experience, and a matched pre- and post-task questionnaire. Consistent with prior research describing veterinary students as individualistic learners, only a third of students spontaneously mentioned learning from each other as one of their most effective strategies. However, when prompted to describe a time when they felt that group members were really learning from each other, students reported highly valuable collaborative learning processes, which they explicitly linked to learning and understanding benefits. Questionnaire data were consistent, showing that students became more positive toward several aspects of the activity as well as toward group work in general. One unexpected finding was the lack of a relationship between students’ self-evaluation of their learning and how well group members knew each other. These findings provide strong support for the educational value of collaborative, case-based learning. In light of other research evidence (using observation data) that the amount of time students actually engage in high-level collaborative processes may be rather limited, this article points to the need for veterinary teachers to better prepare students for group learning activities.
Veterinary Student Attitudes toward Curriculum Integration at James Cook University
Authors: Cavalieri John
Published: October 2009

The aim of this study was to investigate the attitudes of veterinary science students to activities designed to promote curriculum integration. Students (N = 33) in their second year of a five-year veterinary degree were surveyed in regard to their attitudes to activities that aimed to promote integration. Imaging, veterinary practice practicals, and a field trip to a cattle property were classified as the three most valuable learning activities that were designed to promote integration. Veterinary practice practicals, case studies, and palpable anatomy were regarded by students as helping them to learn information presented in other teaching sessions. They also appeared to enhance student motivation, and students indicated that the activities assisted them with their preparation for and performance at examinations. Attitudes to whether the learning exercises helped improve a range of skills and specific knowledge varied, with 39–88% of students agreeing that specific skills and knowledge were enhanced to a large or very large extent by the learning activities. The results indicate that learning activities designed to promote curriculum integration helped improve motivation, reinforced learning, created links between foundational knowledge and its application, and assisted with the development of skills that are related to what students will do in their future careers.
The Importance of Knowledge, Skills, and Attitude Attributes for Veterinarians in Clinical and Non-clinical Fields of Practice: A Survey of Licensed Veterinarians in Quebec, Canada
Authors: Doucet Michèle Y. , Vrins André
Published: October 2009

To improve content validity and the pertinence of outcome assessment tools used for the undergraduate Doctor of Veterinary Medicine program at the University of Montreal's Faculté de médecine vétérinaire, a survey of members of the Quebec veterinary association was conducted. This survey aimed to determine the importance of a list of 71 attributes—categorized as knowledge, general skills, specific skills, and attitudes—for clinical and non-clinical types of professional activities. The results indicated that all basic knowledge components, general skills, and attitudes were equally important for all types of veterinary professional activities, while the importance of specific skills was significantly different for clinical practice and non-clinical fields. It was therefore proposed that outcomes assessment surveys of stakeholders, such as alumni and employers, be analyzed separately for each type of career option.
Anglo-Saxon Law and Scots Law
Authors: Wormald Patrick
Published: October 2009

Patrick Wormald used legal material buried deep in volume i of the Acts of the Parliaments of Scotland to argue for a comparatively maximalist view of early Scottish royal government. The paper compares this Scottish legal material to two Old English codes to show that there existed in Scotland structures of social organisation similar to that in Anglo-Saxon England and a comparable level of royal control over crime by the early eleventh century. The model of a strong judicial regime in the Anglo-Saxon kingdom, put forward fully by Wormald in volume i of The Making of English Law, suggests that the kingdom of the Scots could have been inspired by (or followed a parallel trajectory to) its Anglo-Saxon neighbour in its government's assumption of rights of amendment previously controlled by kin-groups. English influence on Scottish legal and constitutional development can therefore be seen in the tenth and eleventh centuries as much as it can in the twelfth and thirteenth centuries. The paper also suggests methods of examining the legal material in volume i of the Acts of the Parliaments of Scotland and effectively clears the way for further study of this neglected corpus of evidence.
Dying old: and preferably alone? Agency, resistance and dissent at the end of life
Authors: Kellehear Allan
Published: October 2009

Older people who die alone are commonly portrayed negatively in the academic and popular literature. Dying alone is viewed either as an outcome of anti-social behaviour or the result of family, neighbourhood or social services neglect. The idea that people may be exercising agency, resistance or dissent at the end of life and that they do not want attention from services or the wider community receives little or no consideration. By comparing the community and professional views with those of the elderly about end of life preferences, this paper argues that the academic and community image of the elderly as ’’victims’’ has eclipsed the usual ability to see this group in pluralist terms. This stereotype of older people who die alone has negative consequences for sociological and policy analysis.
Oxidative Desulfurization of Fuel Oil by Pyridinium-Based Ionic Liquids
Authors: Zhao Dishun , Wang Yanan , Duan Erhong
Published: October 2009

In this work, an N-butyl-pyridinium-based ionic liquid [BPy]BF4 was prepared. The effect of extraction desulfurization on model oil with thiophene and dibenzothiophene (DBT) was investigated. Ionic liquids and hydrogen peroxide (30%) were tested in extraction-oxidation desulfurization of model oil. The results show that the ionic liquid [BPy]BF4 has a better desulfurization effect. The best technological conditions are: V(IL)/V(Oil) /V(H2O2) = 1:1:0.4, temperature 55 °C, the time 30 min. The ratio of desulfurization to thiophene and DBT reached 78.5% and 84.3% respectively, which is much higher than extraction desulfurization with simple ionic liquids. Under these conditions, the effect of desulfurization on gasoline was also investigated. The used ionic liquids can be recycled up to four times after regeneration.
Estimated Wind River Range (Wyoming, USA) Glacier Melt Water Contributions to Agriculture
Authors: Cheesbrough Kyle , Edmunds Jake , Tootle Glenn , Kerr Greg , Pochop Larry
Published: October 2009

In 2008, Wyoming was ranked 8th in barley production and 20th in hay production in the United States and these crops support Wyoming’s $800 million cattle industry. However, with a mean elevation of 2,040 meters, much of Wyoming has a limited crop growing season (as little as 60 days) and relies on late-summer and early-fall streamflow for agricultural water supply. Wyoming is host to over 80 glaciers with the majority of these glaciers being located in the Wind River Range. These “frozen reservoirs” provide a stable source of streamflow (glacier meltwater) during this critical late-summer and early-fall growing season. Given the potential impacts of climate change (increased temperatures resulting in glacier recession), the quantification of glacier meltwater during the late-summer and early-fall growing seasons is needed. Glacier area changes in the Wind River Range were estimated for 42 glaciers using Landsat data from 1985 to 2005. The total surface area of the 42 glaciers was calculated to be 41.2 ± 11.7 km2 in 1985 and 30.8 ± 8.2 km2 in 2005, an average decrease of 25% over the 21 year period. Small glaciers experienced noticeably more area reduction than large glaciers. Of the 42 glaciers analyzed, 17 had an area of greater than 0.5 km2 in 1985, while 25 were less than 0.5 km2 in 1985. The glaciers with a surface area less than 0.5 km2 experienced an average surface area loss (fraction of 1985 surface area) of 43%, while the larger glaciers (greater than 0.5 km2) experienced an average surface area loss of 22%. Applying area-volume scaling relationships for glaciers, volume loss was estimated to be 409 × 106 m3 over the 21 year period, which results in an estimated 4% to 10% contribution to warm season (July–October) streamflow.
Photogrammetric Methodology for the Production of Geomorphologic Maps: Application to the Veleta Rock Glacier (Sierra Nevada, Granada, Spain)
Authors: De Matías Javier , De Sanjosé José Juan , López-Nicolás Gonzalo , Sagüés Carlos , Guerrero José  Jesús
Published: October 2009

In this paper we present a stereo feature-based method using SIFT (Scale-invariant feature transform) descriptors. We use automatic feature extractors, matching algorithms between images and techniques of robust estimation to produce a DTM (Digital Terrain Model) using convergent shots of a rock glacier.The geomorphologic structure observed in this study is the Veleta rock glacier (Sierra Nevada, Granada, Spain). This rock glacier is of high scientific interest because it is the southernmost active rock glacier in Europe and it has been analyzed every year since 2001. The research on the Veleta rock glacier is devoted to the study of its displacement and cartography through geodetic and photogrammetric techniques.
Investigations of Bread Production with Postponed Staling Applying Instrumental Measurements of Bread Crumb Color
Authors: Popov-Raljić Jovanka V. , Mastilović Jasna S. , Laličić-Petronijević Jovanka G. , Popov Vladimir S.
Published: October 2009

Crumb color quality characteristics of bread of different compositions (whole grain, rye, barley and diet bread) at 24 hours intervals during three days after bread preparation were investigated by means of a MOM-color 100 tristimulus photo colorimeter, in CIE, CIELab, ANLAB and Hunter systems. The highest value of average reflectance y (%) was found for barley bread (immediately after preparation), so that can be said that this sample was “conditionally” the lightest. The lowest values of y (%) were found for diet bread, so that it can be considered as the “conditionally” the darkest product. Colors of all investigated bread samples were lighter after three days of keeping compared to day 0. Changes of average reflectance of bread samples packed in polyethylene packaging with keeping time can be described by linear equation (correlation coefficient 0.99). The dominant wavelength of barley and diet bread confirm the presence of yellow pigment. Color qualities of the mentioned kinds of bread depend on processes during bread staling and raw material composition of bread (flour). Color quality measurements can be used as easy auxiliary method for screening in the development of slower staling bread.
Treatment modalities for hypersplenism in liver transplant recipients with recurrent hepatitis C
Authors: Sibulesky Lena
Published: October 2009

Laparoscopic surgery is the main treatment method for patients with gastrointestinal malignant tumors. Although laparoscopic surgery is minimally invasive, its tool stimulation and pneumoperitoneum pressure often cause strong stress reactions in patients. On the other hand, gastrointestinal surgery can cause stronger pain in patients, compared to other surgeries. Transversus abdominis plane block (TAPB) can effectively inhibit the transmission of nerve impulses caused by surgical stimulation, alleviate patient pain, and thus alleviate stress reactions. Remazolam is an acting, safe, and effective sedative, which has little effect on hemodynamics and is suitable for most patients. TAPB combined with remazolam can reduce the dosage of total anesthetic drugs, reduce adverse reactions, reduce stress reactions, and facilitate the rapid postoperative recovery of patients.
Synthesis and properties of calix[4]arene telluropodant ethers as Ag+ selective sensors and Ag+, Hg2+ extractants
Authors: Lu Yang , Li Yuanyuan , He Song , Lu Yan , Liu Changying , Zeng Xianshun , Chen Langxing
Published: October 2009

Three novel phenyltelluroalkoxyl functionalized tweezer-like calix[4]arenes 6–8 and two monophenyltelluropropoxyl functionalized calix[4]arenes 10 (cone conformer) and 12 (partial cone conformer) were synthesized and characterized. They are good Ag+-selective ionophores in ion-selective electrodes evaluated by electromotive force measurements of polymer membrane electrodes. The tweezer-like ionophores 6–8 showed excellent extraction ability towards Ag+ and Hg2+.
Influence of Defects on Solar Cell Characteristics
Authors: Breitenstein Otwin , Bauer Jan , Altermatt Pietro P. , Ramspeck Klaus
Published: October 2009

The current-voltage (I-V) characteristics of most industrial silicon solar cells deviate rather strongly from the exponential behavior expected from textbook knowledge. Thus, the recombination current may be orders of magnitude larger than expected for the given material quality and often shows an ideality factor larger than 2 in a wide bias-range, which cannot be explained by classical theory either. Sometimes, the cells contain ohmic shunts although the cell’s edges have been perfectly insolated. Even in the absence of such shunts, the characteristics are linear or super-linear under reverse bias, while a saturation would be classically expected. Especially in multicrystalline cells the breakdown does not tend to occur at -50 V reverse bias, as expected, but already at about -15 V or even below. These deviations are typically caused by extended defects in the cells. This paper reviews the present knowledge of the origin of such non-ideal I-V characteristics of silicon solar cells and introduces new results on recombination involving coupled defect levels.
Semi-Insulating Silicon for Microwave Devices
Authors: Jordan Douglas M. , Mallik Kanad , Falster Robert J. , Wilshaw Peter R.
Published: October 2009

The concept of fully encapsulated, semi-insulating silicon (SI-Si), Czochralski-silicon-on-insulator (CZ-SOI) substrates for silicon microwave devices is presented. Experimental results show that, using gold as a compensating impurity, a Si resistivity of order 400 kΩcm can be achieved at room temperature using lightly phosphorus doped substrates. This compares favourably with the maximum of ~180kΩcm previously achieved using lightly boron doped wafers and is due to a small asymmetry of the position of the two gold energy levels introduced into the band gap. Measurements of the temperature dependence of the resistivity of the semi-insulating material show that a resistivity ~5kΩcm can be achieved at 100°C. Thus the substrates are suitable for microwave devices working at normal operating temperatures and should allow Si to be used for much higher frequency microwave applications than currently possible.
Can Impurities be Beneficial to Photovoltaics?
Authors: Luque Antonio , Martí Antonio
Published: October 2009

The state of the art of the intermediate band solar cells is presented with emphasis on the use of impurities or alloys to form bulk intermediate band materials. Quantum dot intermediate band solar cells start to present already attractive efficiencies but many difficulties jeopardize the immediate achievement of record efficiency cells. To complement this research it is worthwhile examining bulk materials presenting an IB. Four or perhaps more materials have already proven to have it and several paths for the research of more are today open but no solar cell has yet been published based on them. This topic has already attracted many researches and abundant funds for their development worldwide.
Properties of Fast-Diffusing Oxygen Species in Silicon Deduced from the Generation Kinetics of Thermal Donors
Authors: Voronkov Vladimir V. , Voronkova G.I. , Batunina A.V. , Golovina V.N. , Falster Robert J. , Cornara M. , Tiurina N.B. , Guliaeva A.S.
Published: October 2009

The generation of Thermal Donors in Si is a nucleation process controlled by several mobile On clusters. The rate-limiting transitions are found to be O1  O2 and O4  O5. The individual transition rates G12 and G45, and also G23 and G34 are deduced from the experimental data. From the transient variation of the generation rate G(t), the equilibrium concentration of the dimers is found, and with it the dimeric diffusivity is also defined. In samples pre-treated at high T, the G(t) dependence has a maximum, due to quenched-in fast-diffusing oxygen monomers (FDMs). The concentration and diffusivity of FDMs were determined.
Interaction of Point Defects with Impurities in the Si-SiO2 System and its Influence on the Properties of the Interface
Authors: Kropman Daniel , Mellikov E. , Lott K. , Kärner Tiit , Heinmaa Ivo , Laas Tony , Medvid Arthur , Skorupa Wolfgang , Prucnal S. , Zvyagin S. , Cizmar E. , Ozerov M. , Woznitsa J.
Published: October 2009

The results of investigation of the point defect generation and interaction with impurities in the Si-SiO2 system during the process of its formation by means of electron paramagnetic resonance (EPR) and nucleous magnetic resonance (NMR) technique are presented. It has been shown that the diference in point defects interaction with hydrogen at the Si-SO2 interface with n- and p-type conductivity are connected with the sign of hydrogen ions incorporation dependence on the Fermi level position in accordance with the proposed model. The interface properties may be improved by laser irradiation.
Anomalous Out-Diffusion Profiles of Nitrogen in Silicon
Authors: Voronkov Vladimir V. , Falster Robert J. , Senkader Semih
Published: October 2009

Out-diffusion nitrogen profiles measured by SIMS after annealing at 850 and 800oC, have a peculiar minimum at a depth of about 5 m. The profiles are well reproduced by simulations assuming that there is a considerable fraction of nitrogen stored in substitutional clusters VN4. Upon annealing, these clusters lose nitrogen and convert into a stable high-temperature form VN1. This reaction involves a preliminary attachment of a fast-diffusing interstitial trimer, N3. Accordingly, the conversion occurs only in the bulk but not at the surface (due to out-diffusion loss of N3), and the substitutional component decreases from the surface towards the bulk. By fitting the profiles, the two basic parameters of the N2/N1 transport are deduced: P = D1K1/2 (a combination of the monomeric diffusivity D1 and the dissociation constant of dimers, K), and the dissociation time of dimers. With these data, D1(T) and K(T) are specified.
DLTS Studies of Carbon Related Complexes in Irradiated N- and P-Silicon
Authors: Makarenko L.F. , Korshunov F.P. , Lastovskii Stanislav B. , Murin L.I. , Moll Michael
Published: October 2009

DLTS studies of transformation kinetics of different carbon–related complexes in electron irradiated n- and p-type silicon have been performed. It has been found that silicon self-interstitials have very low mobility even at room temperature in p-Si, but become extremely mobile under elec-tron injection. It is shown that upon annealing of interstitial carbon in p-Si a metastable state for interstitial carbon-interstitial oxygen complex is formed. This state has an energy level of about Еv+0.36 eV. The formation of the stable and metastable states takes place concurrently. The observed features of the carbon-related complexes formation are likely related to the existence of different crystallographic orientation of the equiprobable pathways through which the interstitial carbon and oxygen atoms can approach each other.
Oxygen Diffusion in Si1-xGex Alloys
Authors: Khirunenko Lyudmila I. , Pomozov Yu.V. , Sosnin Mikhail G. , Duvanskii A.V. , Golyk S.K. , Abrosimov Nikolay V. , Riemann H.
Published: October 2009

The measurements of stress induced dichroism on oxygen absorption band near 1107 cm-1 in Si1-xGex compounds and subsequent kinetics of the dichroism recovery upon isothermal annealing have been carried out. It has been found that the magnitude of introduced by uniaxial stress dichroism decreases with increasing Ge content. Two components in the dichroism annealing kinetics have been found. On the basis of studying absorption spectra of samples under investigations it was assumed that two components in relaxation correspond to the diffusion of oxygen being in a different nearest environment: the one component corresponds to oxygen surrounded by silicon atoms and the second one to the oxygen the neighbour of which is Ge atom. Diffusivity for each of the components has been determined. It has been shown that the diffusivity of oxygen that is in both of these configurations decreases with increasing Ge content.
Grain Boundaries in Multicrystalline Si
Authors: Chen Jun , Chen Bin , Lee Woong , Fukuzawa Masayuki , Yamada Masayoshi , Sekiguchi Takashi
Published: October 2009

We report the electrical, structural and mechanical properties of grain boundaries (GBs) in multicrystalline Si (mc-Si) based on electron-beam-induced current (EBIC), transmission electron microscope (TEM), and scanning infrared polariscope (SIRP) characterizations. The recombination activities of GBs are clearly classified with respect to GB character and Fe contamination level. The decoration of Fe impurity at boundary has been approved by annular dark field (ADF) imaging in TEM. Finally, the distribution of residual strain around GBs, and the correlations between strain and electrical properties are discussed.
Optimization of Silicon Ingot Quality by the Numerical Prediction of Bulk Crystal Defects
Authors: Loix F. , Dupret Francois , de Potter A. , Rolinsky R. , Van den Bogaert N. , Regnier V.
Published: October 2009

In this paper a numerical model is investigated to predict and optimize the quality of
Czochralski-grown silicon single crystals. The different mechanisms governing the formation,
transport, recombination, nucleation and growth of point- and micro-defects in the crystal are put
together with a view to getting a reliable picture of the entire set of physical effects governing the
crystal quality. Numerical experiments are conducted to illustrate the model predictions.
Rate Equation Modeling, Ab Initio Calculation, and High Sensitive FTIR Investigations of the Early Stages of Oxide Precipitation in Vacancy-Rich CZ Silicon
Authors: Kissinger G. , Dabrowski J. , Akhmetov V.D. , Sattler Andreas , Kot D. , von Ammon Wilfried
Published: October 2009

The results of highly sensitive FTIR investigation, ab initio calculations and rate equation modeling of the early stages of oxide precipitation are compared. The attachment of interstitial oxygen to VOn is energetically more favorable than the attachment to On for n  6. For higher n the energy gain is comparable. The point defect species which were detected by highly sensitive FTIR in high oxygen Czochralski silicon wafers are O1, O2, O3, and VO4. Rate equation modeling for I, V, On and VOn with n = (1..4) also yields O1, O2, O3 to appear with decreasing concentration and VO4 as that one of the VOn species which would appear in the highest concentration after RTA.
Oxygen Precipitation in Conventional and Nitrogen Co-Doped Heavily Arsenic-Doped Czochralski Silicon Crystals: Oswald Ripening
Authors: Ma Xiang Yang , Feng Yan , Zeng Yu Heng , Yang De Ren
Published: October 2009

Oxygen precipitation (OP) behaviors in conventional and nitrogen co-doped heavily arsenic-doped Czocharalski silicon crystals subjected to low-high two-step anneals of 650 oC/8 h + 1000 oC/4-256 h have been comparatively investigated. Due to the nitrogen enhanced nucleation of OP during the low temperature anneal, much higher density of oxygen precipitates generated in the nitrogen co-doped specimens. With the extension of high temperature anneal, Oswald ripening of OP in the nitrogen co-doped specimens preceded that in the conventional ones. Moreover, due to the Oswald ripening effect, the oxygen precipitates in the conventional specimens became larger with a wider range of sizes. While, the sizes of oxygen precipitates in the nitrogen co-doped specimens distributed in a much narrower range with respect to the conventional ones.
Defect Generation during Plastic Deformation of Si-Rich Cz-Grown SiGe Crystals
Authors: Yarykin Nikolai , Abrosimov Nikolay V.
Published: October 2009

The IR absorption spectra and kinetics of the oxygen solid solution decay were studied in the Si1¡xGex crystals (0 · x · 0:055) plastically deformed at 680±C up to the 2{5% residual strain. It is found that the defects of non-dislocation nature, the dislocation trails, are formed during the plastic deformation of all studied SiGe crystals. The ¯ne structure of the IR absorption spectra around the 1000 cm¡1 wave number is found to be nearly identical in the pure Si (no Ge) samples and Si1¡xGex crystals with x · 0:02. At higher x the ¯ne structure was not detected due to the alloy-related broadening. In all studied crystals, the decay of the supersaturated oxygen solid solution at 650±C is determined by oxygen agglomeration at the dislocation trails as shown by the comparison with the samples annealed at 1150±C.
Accumulation of Hydrogen within Implantation-Damaged Areas in Processed Si:N and Si:O
Authors: Misiuk Andrzej , Ulyashin Alexander G. , Barcz Adam , Formanek Peter
Published: October 2009

Accumulation of hydrogen in Czochralski silicon implanted with N2+ (Si:N; N dose, DN=1–1.8x1018 cm-2; energy E=140 keV) or O2+ (Si:O; DO=1x1017 cm-2; E=200 keV), processed at up to 1400 K (HT) under enhanced Ar pressure, up to 1.2 GPa (HP), and followed by treatment in hydrogen (deuterium) plasma, was investigated by Secondary Ion Mass Spectroscopy. Implantation produces buried amorphous layer. As determined by transmission electron microscopy, subsequent HT-HP processing results in a formation of a specific sample microstructure.
In plasma treated as-implanted Si:N, hydrogen accumulates at a depth of about 50 nm, up to concentration 2x1021 cm-3. This concentration is twice lower at a depth ≈ 80–250 nm. Deuterium content remains almost unchanged after plasma treatment of Si:N prepared by processing at 1270 K while it is strongly dependent on DN and on HP. In plasma treated Si:O, prepared by processing at 920-1230 K, hydrogen profile corresponds to that of implanted oxygen and decreases with HP.
Comparative analysis of hydrogen accumulation and its subsequent release at 720-920 K in the Si:N and Si:O structures indicates that the capacity of buried layers in Si:O to getter and to preserve hydrogen is higher than that in Si:N.
Growth of Silicon Carbide Filaments in Multicrystalline Silicon for Solar Cells
Authors: Möller Hans Joachim , Funke Claudia , Bauer Jan , Köstner S. , Straube H. , Breitenstein Otwin
Published: October 2009

This work introduces two different approaches to explain the growth of silicon carbide (SiC) filaments, found in the bulk material and in grain boundaries of solar cells made from multicrystalline (mc) silicon. These filaments are responsible for ohmic shunts. The first model proposes that the SiC filaments grow at the solid-liquid interface of the mc-Si ingot, whereas the second model proposes a growth due to solid state diffusion of carbon atoms in the solid fraction of the ingot during the block-casting process. The melt interface model can explain quantitatively the observed morphologies, diameters and mean distances of SiC filaments. The modeling of the temperature- and time-dependent carbon diffusion to a grain boundary in the cooling ingot shows that solid state diffusion based on literature data is not sufficient to transport the required amount of approximately 3.4  1017 carbon atoms per cm2 to form typical SiC filaments found in grain boundaries of mc-Si for solar cells. However, possible mechanisms are discussed to explain an enhanced diffusion of carbon to the grain boundaries.
Bulk Passivation of Defects in Multi-Crystalline Silicon Solar Cells by a-SiNx:H Layers
Authors: Cornagliotti Emanuele , Dekkers Harold F.W. , Prastani Caterina , John Joachim , Van Kerschaver Emmanuel , Poortmans Jef , Mertens Robert P.
Published: October 2009

In this work the impact of hydrogenation from hydrogen-rich amorphous silicon nitride (a-SiNx:H) on dislocations and grain boundaries in multi-crystalline silicon (mc-Si) solar cells is presented. Layers are deposited by means of plasma enhanced chemical vapor deposition (PECVD). Electrical bulk passivation is provided during thermal annealing, in which hydrogen diffuses from a-SiNx:H. The passivation effect is discussed in terms of recombination centers and non-recombinative charge traps reduction as well as in terms of local short circuit current improvement in specially manufactured solar cells.
Study of Internal versus External Gettering of Iron during Slow Cooling Processes for Silicon Solar Cell Fabrication
Authors: Hofstetter Jasmin , Lelièvre Jean F. , del Cañizo Carlos , Luque Antonio
Published: October 2009

The eect of slow cooling after dierent high temperature treatments on the in-
terstitial iron concentration and on the electron lifetime of p-type mc-Si wafers has been in-
vestigated. The respective impacts of internal relaxation gettering and external segregation
gettering of metal impurities during an extended phosphorous diusion gettering are studied.
It is shown that the enhanced reduction of interstitial Fe during extended P-gettering is due to
an enhanced segregation gettering while faster impurities like Cu and Ni are possibly reduced
due to an internal gettering eect.
Analysis of Silicon Carbide and Silicon Nitride Precipitates in Block Cast Multicrystalline Silicon
Authors: Holla M. , Arguirov Tzanimir , Seifert Winfried , Kittler Martin
Published: October 2009

We report on the optical and mechanical properties of Si3N4 inclusions, formed in the upper part of mc-Si blocks during the crystallization process. Those inclusions usually appear as crystalline hexagonal tubes or rods. Here we show that in many cases the Si3N4 inclusions contain crystalline Si in their core. The presence of the Si phase in the centre was proven by means of cathodoluminescence spectroscopy and imaging, electron beam induced current measurements and Raman spectroscopy. The crystalline Si3N4 phase was identified as β-Si3N4. Residual stress was revealed at the particles. While the stress is compressive in the Si material surrounding the Si3N4 particles tensile stress is found in the Si core. We assume that the stress is formed during cool down of the Si block and is a consequence of the larger thermal expansion coefficient of Si in comparison to that of β-Si3N4. Iron assisted nitridation of Si at temperatures below 1400 °C is considered a possible mechanism of Si3N4 formation.
Comparative Study of Electrical and Optical Properties of Plastically Deformed Silicon
Authors: Yarykin Nikolai , Feklisova Olga V.
Published: October 2009

The Czochralski-grown silicon crystals plastically deformed at 680±C to the residual
strain of 5% and subsequently annealed in the temperature range of 650{850±C were studied
by the IR absorption and DLTS techniques. The formation and disappearance kinetics were
investigated for several weak IR absorption lines around the 1000 cm¡1 wave number, which
were previously related to the deformation-induced defects of non-dislocation nature in the
dislocation trails. In parallel, the spectrum and concentrations of the deep-level centers in the
upper half of the gap were measured by DLTS. It is found that the deep-level centers and op-
tically active defects exhibit a common behavior during the post-deformation heat treatments.
However, a direct correspondence between the IR and DLTS features cannot be established be-
cause of the higher concentration of the deep-level centers as compared to the optically active
defects.
Spatially Resolved Defect Analysis in Cz-Silicon after Copper-Nickel Co-Precipitation by Virtue of Light-Beam-Induced Current Measurements
Authors: Saring P. , Rudolf C. , Stolze L. , Falkenberg A. , Seibt Michael
Published: October 2009

We report on a light-beam-induced current (LBIC)-analysis of metal silicide defects arising from co-precipitation of copper and nickel in Cz-silicon-bicrystals produced by wafer direct bonding. Large colonies of silicide precipitates in the one wafer emerging from undisturbed growth from few nucleation sites were observed in different orientations with respect to the surface which correspond to Si {110} planes. From this, the colonies formed during copper-nickel co-precipitation reveal the same attributes as those colonies typical for copper precipitation in the absence of nickel. Oxygen related defects associated with a higher defect distribution in the other wafer were characterized by means of high resolution Transmission Electron Microscopy (TEM) and their temperature dependent LBIC signal.
In Situ Observation of Oxygen Precipitation in Silicon with High Energy X-Rays
Authors: Grillenberger Hannes , Magerl Andreas
Published: October 2009

Oxygen precipitation in silicon has been studied in-situ by high energy X-ray diffraction. A gain of diffracted intensity is expected if an ideal crystal is distorted by growing precipitates as the diffraction mode changes from a dynamical to a more kinematical one. Irreversible changes in the intensity of a 220 and a 400 Bragg peak are detected for Czochralski grown samples only, but not in a float zone grown reference crystal. Thus, these changes are attributed to oxygen precipitation, which is confirmed by a subsequent classical ex-situ characterization. Further, the changes of the intensities of the two measured Bragg peaks are compared to each other to get the level of change in the diffraction mode from a dynamical to a kinematical one. The detection limit of the specific setup is estimated via a simulation of the defect inventory to correspond to a precipitate diameter of 50nm with the density of 6.9•109 1/cm3.
The diffraction experiments are done with polychromatic and divergent X-rays generated by a laboratory source, albeit with high energy. This results in a simple and accessible setup for the characterization of oxygen precipitates.
Point Defects in γ-Irradiated Germanium: High- and Low- Momentum Positron Annihilation Study Before and After n-p-Conversion
Authors: Arutyunov N.Yu. , Emtsev Valentin V. , Krause-Rehberg Reinhard
Published: October 2009

The electron momentum distribution and microstructure of centers incorporating a vacancy (vacancies) and a group-V-impurity atom (P, As, Sb, or Bi) in oxygen-lean n-Ge crystals have been investigated by means of the angular correlation of the annihilation radiation (ACAR). The vacancy-group-V-impurity atom complexes have been induced by irradiation with 60Co γ – rays at Tirr. ≈ 280K. A split between the intensities of the high-momentum emission of the annihilation radiation measured before and after n-p-conversion has been revealed for the complexes containing smaller ion cores (P, As) and the larger ones (Sb, Bi), respectively. After n-p-conversion the electron density decreases slightly (but markedly) around the positron localized at the vacancy complexes incorporating P, Sb, and Bi impurity atom. This decrease is accompanied by a lessening of intensity of the high-momentum emission of the annihilation radiation thus bringing in a direct evidence of a multi-vacancy structure of the vacancy-group-V-impurity atom complexes after n-p-conversion; the electron density was found to be affected by the localized deep acceptor states related to these centers. The relaxation inward open volume is a common feature which is pronounced for As-containing complexes. Subvalent band states are suggested to contribute the high-momentum annihilation most markedly. The electron momentum density around the positron is due to rather by the elemental specificity of the surrounding atoms than by changes of the electron-positron many-body interaction in the vacancy-group-V-impurity atom complexes.
Defect Characterization of Poly-Ge and VFG-Grown Ge Material
Authors: Holla M. , Arguirov Tzanimir , Jia G. , Kittler Martin , Frank-Rotsch C. , Kiessling F.M. , Rudolph P.
Published: October 2009

Germanium is an attractive model system for studying the crystallization mechanism and optimization of the growth processes in photovoltaics. In comparison to Si it has a lower melting point and that is why its usage is cost effective. The main aim of our work was to verify the similarities in the growth related defect formation between Ge and Si. We apply standard Si characterization methods to poly and VGF-grown n-type Ge. Room temperature and 80 K EBIC measurements were done to reveal the defect structure. Photoluminescence spectra were used to characterize the optical properties as for instance the Ge band-to-band or defect originated transitions. Additionally, photoluminescence and cathodoluminescence maps were preformed to reveal the defect distribution/activity, too, by using the direct Ge band-to-band transition.
Cathodoluminescence of SiO2/Si System
Authors: Zamoryanskaya M.V.
Published: October 2009

In this paper the new method for determination of luminescent centers concentration are discussed. While the possibility of electron traps determination and definition of its activation energy are suggested. The cathodoluminescent (CL) method was used. The determination of luminescent centers concentration in silicon oxide is based on the measurements of dependences of CL intensity on electron beam current. The presence and energy of activation of electron traps were studied by measurement of rise time and decay of luminescent band during the stationary irradiation of silica by electron beam.
Correlation Study of Morphology, Electrical Activation and Contact formation of Ion Implanted 4H-SiC
Authors: Weng Ming Hung , Roccaforte Fabrizio , Giannazzo Filippo , di Franco Salvatore , Bongiorno Corrado , Zanetti Edoardo , Ruggiero Alfonso , Saggio Mario , Raineri Vito
Published: October 2009

This paper reports a detailed study of the electrical activation and the surface morphology of 4H-SiC
implanted with different doping ions (P for n-type doping and Al for p-type doping) and annealed at
high temperature (1650–1700 °C) under different surface conditions (with or without a graphite
capping layer). The combined use of atomic force microscopy (AFM), transmission electron
microscopy (TEM), and scanning capacitance microscopy (SCM) allowed to clarify the crucial role
played by the implant damage both in evolution of 4H-SiC surface roughness and in the electrical
activation of dopants after annealing. The high density of broken bonds by the implant makes surface
atoms highly mobile and a peculiar step bunching on the surface is formed during high temperature
annealing. This roughness can be minimized by using a capping layer. Furthermore, residual lattice
defects or precipitates were found in high dose implanted layers even after high temperature annealing.
Those defects adversely affect the electrical activation, especially in the case of Al implantation.
Finally, the electrical properties of Ni and Ti/Al alloy contacts on n-type and p-type implanted regions
of 4H-SiC were studied. Ohmic behavior was observed for contacts on the P implanted area, whilst
high resistivity was obtained in the Al implanted layer. Results showed a correlation of the electrical
behavior of contacts with surface morphology, electrical activation and structural defects in
ion-implanted, particularly, Al doped layer of 4H-SiC.
Current Status of Graphene Transistors
Authors: Lemme M.C.
Published: October 2009

This paper reviews the current status of graphene transistors as potential supplement
to silicon CMOS technology. A short overview of graphene manufacturing and metrology
methods is followed by an introduction of macroscopic graphene field effect transistors (FETs).
The absence of an energy band gap is shown to result in severe shortcomings for logic
applications. Possibilities to engineer a band gap in graphene FETs including quantum
confinement in graphene Nanoribbons (GNRs) and electrically or substrate induced asymmetry
in double and multi layer graphene are discussed. Novel switching mechanisms in graphene
transistors are briefly introduced that could lead to future memory devices. Finally, graphene
FETs are shown to be of interest for analog radio frequency applications.
Scaling in Quantum Transport in Silicon Nano-Transistors
Authors: Wulf Ulrich , Richter Hans
Published: October 2009

We develop a theory for scaling properties of quantum transport in nano-field effect transistors. Our starting point is a one-dimensional effective expression for the drain current in the Landauer-Büttiker formalism. Assuming a relatively simple total potential acting on the electrons the effective theory can be reduced to a scale-invariant form yielding a set of dimensionless control parameters. Among these control parameters are the characteristic length l and -width w of the electron channel which are its physical length and -width in units of the scaling length . Here is the Fermi energy in the source contact and is the effective mass in the electron channel. In the limit of wide transistors and low temperatures we evaluate the scale-invariant i-v characteristics as a function of the characteristic length. In the strong barrier regime, i. e. for long-channel behavior is found. At weaker barriers source-drain tunneling leads to increasingly significant deviations from the long-channel behavior.
Feedback Effect on the Self-Organized Nanostructures Formation on Silicon upon Femtosecond Laser Ablation
Authors: Varlamova Olga , Ratzke Markus , Reif Jürgen
Published: October 2009

The role of multi-pulse feedback in self-organized nanostructure (ripples) formation on silicon surface upon femtosecond laser ablation is investigated. For irradiation at constant intensity and pulse repetition rate, the previously postulated feedback effect of accumulated dose with in¬creasing number of pulses is confirmed and investigated in detail: both the modified surface area as well as the complexity and feature size of generated nanostructures increase with accumulated dose. More interestingly, at constant total incident dose (number of pulses times pulse energy) accumu¬lation and feedback depend strongly on temporal pulse separation. The feedback becomes increas¬ingly weaker with increasing time intervals between successive pulses, involving times up to one second and more before individual pulses act independently. In a first attempt to model this long-lived coupling, we find that conduction band electrons, produced by the preceding laser pulse, can provide, indeed, such feedback by facilitating coupling of subsequent pulses for substantial delays. However, the achieved time span of about a millisecond is still significantly shorter than observed experimentally.
Confinement Levels in Passivated SiGe/Si Quantum Well Structures
Authors: Antonova I.V. , Neustroev E.P. , Smagulova S.A. , Kagan M.S. , Alekseev P.S. , Ray S.K. , Sustersic N. , Kolodzey J.
Published: October 2009

The set of quantum confinement levels in SiGe quantum wells (QW) was observed in the temperature range from 80 to 300 K by means of charge deep-level transient spectroscopy (Q-DLTS) and transport measurements. These observations proved possible due to a passivation of structure surface with organic monolayer deposition. Si/SiGe/Si structures with different Ge contents in SiGe layer were studied. The confined levels in passivated structures became apparent through DLTS measurements as various activation energies in temperature dependence of the rate of carrier emission from QW. It was found that the recharging of SiGe QWs and carrier emission accomplish due to thermo-stimulated tunneling. The steps in the current-voltage characteristics originated from direct tunneling via the confined states were found to determine the current flow at high fields.
Silicon Periodic Structures and their Liquid Crystal Composites
Authors: Astrova Ekaterina V. , Tolmachev V.A. , Zharova Yulia A. , Fedulova Galya V. , Baldycheva A.V. , Perova Tatiana S.
Published: October 2009

This paper summarises results on the design, fabrication and characterisation of one-dimensional (1D) Photonic Crystals (PCs) for silicon micro-photonics. Anisotropic and photo-electrochemical etching were used to obtain silicon wall arrays with a high aspect ratio. The characteristics of these wet etching techniques, including their advantages and disadvantages are considered. Optical reflection and transmission spectra of the photonic structures fabricated were characterised by Fourier Transform Infra-Red (FTIR) micro-spectroscopy over a wide spectral range of =1.5-14.5m. These measurements reveal that side-wall roughness impacts the optical properties of 1D PCs. Problems associated with Photonic Band-Gap (PBG) tuning in periodic structures infiltrated with nematic liquid crystals are discussed. A design of a composite 1D PC on an SOI platform for electro-tuning is proposed. The structure was fabricated and tuning due to an electro-optical effect with E7 liquid crystal filler was demonstrated.