Archive April, 2011

Sizes of crystallites as a function of cooling rate

A.S. Bakin, V.N. Romanenko, J. Schilz, G.V. Nikitina, and D.I. Ivanov

The effective function model of phase transitions (1) has been applied to the process of crystallisation of the segregating solid solutions PblxSnxTe and Gel xSix in order to determine the values of the maximum sizes of crystallites and the effective diffusion coefficients for the liquid phase.

The model has already been checked in a number of investigations (2) and the references herein), but verification of the maximum possible size of a crystallite Lmjx for a binary system that undergoes a certain rate of temperature drop w is still lacking. The theory obtains the simple relation (3):

Read more.. »

Vladimir Romanenko, Vladimir Bystrov, Viktor Zherdev, Khafiz Mellekh

Saint-Petersburg State University of Architecture and Civil Engineering ( 4, 2-nd Krasnoarmeiskaya at., St-Peteraburg, 198005, Russia ).

Two types of building and housing testing instruments are described in this report. The first one based on the semiconductor conductivity changes of the small point, linear or planar probe. Dependence of CdP2 optical properties is the base of the second instrument groupe. Principles of the first group instruments work is represented on the Current from the source E heated special small heater #. Heater temperature is measured with the aid of thermoiesistor R. TYansformed value of resistor resistivity may be seen on the special screen S or on the digital/analogous display. In some constructions thermoresistor may be changed for thermocouple.

The heater and the thermoresibior are assembled in a small probe. Globe form is the usual form of this assemble. The amount of globe is no more than 1-3 mm in diameter. Power and measuring wires run throw small metall tube. Its diameter is no more than 3-5 mm ( The length of the tube is no less than 100 mm. Different -planar and cilindrical – geometries are also possible. The theory of such a probe measuring is described in[l].

Read more.. »

M.Dvinyaninov, V.N.Romanenko

Solidification features of high purity substances used as temperature reference points have bean considered using analytical and numerical methods. The cases of planar and cylindrical solidification are studied. A series of peculiarities is first revealed being of a certain practical interest. Calculated results are compared with available experimental data of other authors.

Аналитически и численно изучаются особенности кристаллизации особо чистых веществ, применяемых для создания реперов температурной шкалы. Изучены два случая — плоской и цилиндрической кристаллизации. При этом впервые обнаружен ряд особенностей, представляющих определенный практический интерес. Результаты расчетов сравнены с имеющимися экспериментами других авторов.

Directional solidification (DS) is widely used in many scientific and technological fields, such as crystal growth, purification, temperature reference points etc. In many cases, it is necessary to know the impurity redistribution at DS in various conditions (phase transition rate, physical properties of materials, layers width, sample geometry etc).

Read more.. »

V.Romanenko, Ya.Sergeeva, D.Ivanov, I.Saunin

Saint-Petersburg State University of Architecture and Civil Engineering, 4, 2-nd Krasnoarmeiskaya st., Saint-Petersburg, 198005, Russia *Saint-Petersburg Electrotechnical University, 5 Prof. Popova st., Saint-Petersburg, 197022, Russia

Semiconductor AIVBVI compounds are of great interest for applications in infrared techniques [1]. Study of growing and electrical properties of PbS and PbTe thin films on silicon substrates are presented in this work.

Samples were prepared by vacuum condensation of PbS and PbTe on substrates using the «hot wall» technique [2]. To provide a proper structure perfectness of layers, the intermediate buffer layers of CaF2 and BaF2 were preliminary grown on the silicon substrate. Growth conditions are shown in the Table below.

Read more.. »