Archive March, 2011

Bulk growth of silicon – germanium solid solutions

This paper provides an overview of the technology for growing bulk silicon-germanium solid solutions and of the structural properties of the solidified materials.

It is an attempt to summarize and value the methods and efforts applied to the controlled crystallization of silicon germanium melts which were employed during the last four decades.

The especially high degree of segregation makes the system sensitive to small changes of growth conditions, which leads to inhomogeneities and strain. The future availability of homogeneous, low-defect Si-Ge crystals through the whole composition range is briefly discussed

V.Romanenko, G.Nikitina
Department of Physics, St.-Petersburg State University of Architecture and Civil Engineering, 4,2-nd Krasnoarmeiskaya St., 198005, St.-Petersburg, Russia. Department of Physics, St.Petersburg Technological Institute, 26 Moskovskii Ave., 198013, St.-Petersburg, Russia.
Methods for determing distribution coefficients and solubility curves based on analysis of effective distribution coefficients are examined. Examples are given for Ge-impurity, Ge-Si and InSb-GaSb systems. For Те, Pb, Sn, Sb, Se impurities in Bi, influence of current density on distribution coefficient when d.c. flows through the solid/liquid interface has been investigated. For the same case, magnetic field effect on this dependence has been studied. A method to determine the volatile impurity distribution is described.

It has been used to determine distribution coefficients of Zn, Те and Sm in GaAs. It is shown that analysis of distribution coefficients in complex systems allows to determine the chemical form in which an impurity enters the crystal matrix. The method has been used to study the behaviour of impurities in Bi2Te3. It is shown that impurities introduced into Bi2Te3 in the form of halides may partially dissociate in the melt. The phenomenon of maxima arising on concentration curves during the solidification of complex systems is described.

Analysis of that phenomenon has shown that choosing initial conditions for the crystallization of an epitaxial layer, one can control the shape of the composition distribution curve as a function of the epilayer thickness. Use of additional feeding of the liquid phase to determine the physico-chemical system parametrs has been considered. Making use of the methods developed, solubility curves of Dy, Gd and Sm in GaAs have been found. The second of proposed methods has been used for the analysis of GaAs-impurity systems. The so-called thermal arrest process is described. It allows to find the impurity distribution coefficient without measuring its concentration in the solid phase. The method has been checked for the case of In impurity in GaAs.

Department of Physics, Saint-Petersburg State University of Architecture and Civil Engineering
(4, 2-nd Krasnoarmeiskaya st., St.-Petersburg, 198005, Russia)
Small semiconductor sensors have some advantages in air quality and thermal conditions of interioir apartments control. The main of these sensor’s advantages are small sizes and universality. Some sensors are produced on Sn02 films. It is possible to detect air pollutions of different kind with these sensor’s help. Some problems with results interpretation may be overcome with the help of new instrumental constructions described in the report.
Seria of thermophysical sensors described in the report permits to study humidity, air flows velocities, thermoflows throw walls and ceelings behaviours and some other valuable housing parameters. These sensors construction is based on special type of point thermoresistors disposed in the end of the thin tube. Some technical data of described sensors are discussed. Results of the sensor usage in appartment parameters control for cold climate conditions are described.

Full text of presentation

Romanenko V., Nikitina G.
Saint-Petersburg Branch of Academy of Informatics
Technologies in Education
Saint-Petersburg, Russia
Romanenko V., Nikitina G.Saint-Petersburg Branch of Academy of InformaticsTechnologies in EducationSaint-Petersburg, Russia

Different intercultural contacts are widely distributed in the modern world. That is why the faculties have to cultivate tolerance in their students. All students must have a good will for understanding persons of different confessions, races, nations, ages, sexuality and professions. How to do it? The most part of stresses and conflicts is created as a result of discrepancies in surrounding environment. There are two typical mistakes we meet at the discussion of intercultural problems. The first one is connected with assumption that it is possible to destroy all discrepancies in the world and to build non-conflict situation on this base. The second one is assumption it is necessary to study the leading conflicts only. The national and language contradictions are studied in the first order in this case. Yet the most part of other problems is usually not in the area of study. These problems can create serious stresses in real life. It is impossible to create full homogeneity in external environment. Continues struggle between tendency to homogeneity and opposite tendency to stratification takes place in the each part of our world. Have we produce homogeneity on the one level of the human society the new stratification with its own contradictions immediately is created in its other part. That means we are living in a highly diversity world. This situation is not accidental. So we have to study the life in a very complex and diverse environment.

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Physics in Higher Education

«Physics in Higher Education»
JOURNAL of the
MOSCOW
PHYSICAL
SOCIETY Series «B»
V. 2, N 2, 1996

In this article, we propose a new educational method intended to develop creative engineering abilities in younger university students [1], This method was successfuly applied for a number of years in a physics laboratory course.

The main results of our studies are presented here. T he primary idea of the proposed approach is a so-called «method of repeated investigation» [2]. In this method, the students are invited to independently study several microproblems, The results of these studies are, of course, known to the instructors, but are absolutely unknown to the students. Without a doubt, the instructor helps the students solve these problems, but this help is not direct.

The instructor asks a number of special questions, and in some cases gives the students some hints, In the proposed method, assigned exercises and problems connected with them are the same as in usual accepted methods. The novelty in our method lies in the series of special questions. The basis for these questions is the same for all types of exercises. Thus, in working on different exercises, the student must solve the same supplementary problems in each case. These supplementary problems should develop the creative ability of the student.

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Vladimir Romanenko, Larisa Malinovska, Galina Nikitina

The present article summarises some findings of educators from St. Petersburg and Jelgava in the research in competences and skills necessary for engineers and the ways how to improve the process of studies to develop them applying different new methods.

Exchanging of experience among teachers and sharing ideas help a lot to make this process faster and easier; co-operation among teachers promotes also co-operation among students and it, in turn, disseminates information not only at national but also international level. Teachers and students can learn a lot from one another and it allows for omitting of some unnecessary stages in the research processes.

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Sergei Abramovich, Galina V. Nikitinay,Vladimir N. Romanenkoz

The paper describes a number of practical uses of a spreadsheet that vary across the noviceexpert continuum in terms of the development of skills required for career paths in the STEM (science, technology, engineering, mathematics) disciplines. To this end, three types of skills are introduced: basic, professional and advanced. Using a spreadsheet as a background and Vygotskian perspective on learning and development as a conceptual framework, the paper demonstrates how purposeful applications of the skills transform one type into another, encourage concept learning, and broaden technology integration into problem solving. The relationship between a spreadsheet and other software tools is discussed.

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