S.N. Rossolenko

Czochralski growth of Si- and Ge-rich SiGe single crystals

Si 1-x Ge x single crystals (0 < x < 0.15) with diameter up to 2 in were grown by conventional Czochralski technique. The method for the growth of Ge 1-x Si x crystals using continuous feeding the melt with a number of Si rods was developed and the Ge 1-x Si x crystals (0 < x < 0.3) were grown. The growth process both Si 1-x Ge x and Ge 1-x Si x crystals was carried out using the automated control system based on the crystal weighing. The peculiarities of weight control at the stage of conical part formation are considered.

Growth of shaped sapphire crystals using automated weight control

Abstract The automated control systems have been developed for the growth of various sapphire crystals by edge-defined film-fed growth (EFG) and noncapillary shaping (NCS) methods. Automated crystal weight control is based on the analysis of the behaviour of the mass rate deviation at all stages of the growth process (seeding, crystal expansion, stationary growth, in-situ cross-sectional changing). The maintenance of the mass rate deviation in a certain range provides the crystal quality control as well as crystal shape control.

Menisci masses and weights in Stepanov (EFG) technique: ribbon, rod, tube

Abstract The present paper deals with the integration of the famous Laplace equation resulting in the expressions of full mass and weight of the liquid menisci in the system “melt–crystal” during the crystal growth process by Stepanov (EFG) technique. The problem for the cases of growing ribbon, cylindrical rod, cylindrical tube, rod of arbitrary cross-section and tube of arbitrary inner and outer cross-sections is solved. The problem for a hydrostatic approximation of the menisci of growing crystals is solved and it is shown via an analysis of the full energy functional, that the hydrodynamic factor is too small to be considered in the automated crystal growth systems.

Growth of Sapphire Ribbons with Capillary Channels for Laser Spectroscopy

Sapphire ribbons with extended capillary channels 450–600 μm in diameter were grown from melt by the Stepanov technique in order to develop a new scalpel capable of fluorescent diagnostics of the state of biological tissue. An automated system was built which allows one to control the shape and quality of sapphire ribbons at all growth stages.

Examination of Si1-xGex Laterally Graded Crystals for Use in High Brilliance Synchrotron Beams

We report about the feasibility of employing laterally graded Si 1-x Ge x crystals as x-ray monochromators for synchrotron radiation beams. This type of crystals can be used in a divergent beam with nearly the same energy resolution and spectral flux as a regular crystal in a parallel beam. The effect is achieved due to continous changes in the lattice parameter with varying Ge concentration in the Si crystal. Theoretical calculations for BESSY II dipole radiation show, that the optimum gradient of Ge along the surface should be about 1.0 at. % per cm. The properties of the crystals have been investigated by x-ray diffraction and fluorescence analysis with radiation from a conventional x-ray tube. We found nearly perfect crystal quality for Ge concentrations up to 7.0 at. % and gradients of Ge up to 1.1 at. % Ge per cm which would already be sufficient for applications in the x-ray monochromator.

Terahertz waveguides based on multichannel sapphire shaped crystals

In this paper, an advantage of sapphire shaped crystal use for highly efficient terahertz (THz) waveguiding is discussed. The THz photonic crystal waveguide has been manufactured using the edge-defined film-fed growth (EFG) or Stepanov technique of shaped crystal growth. The effective mode index and extinction coefficient of the waveguide have been experimentally studied using the THz pulsed spectroscopy. The observed results have shown that the multichannel sapphire crystal allows guiding the THz waves with minimal dispersion in frequency range of 1:0 to 1:55 THz and minimal loss of 2 dB/m at 1:45 THz. The waveguides based on sapphire shaped crystals can be employed in wide range of THz technology applications, including non-destructive evaluation of materials, medical diagnostics, and sensing in aggressive environment.

Adaptable monochromators to optimize intensity gain and resolution for experiments with high-energy synchrotron radiation

We present investigations of bendable comb-shaped Si crystals and Si1-xGex gradient crystals, tested in Laue geometry, to be used as monochromator and analyzer for triple crystal x-ray diffractometry with high (around 100 keV) energy synchrotron radiation. At these energies, both the high q- space resolution of synchrotron radiation and the high penetration power of neutrons are present. The overall resolution element in q-space is usually dominated by the properties of the sample. A comb crystal structure can provide a gain in integrated intensity of up to a factor of 70, compared to perfect Si crystal monochromator and analyzer, by adjusting the instrumental resolution to the needs of a sample. However, this intensity gain can further be increased by using Si1-xGex gradient crystals. The continuously- changing lattice parameter in these crystals yields an increase in maximum peak reflectivity of up to 100% in comparison to theoretical limit of 50% for normal crystals in Laue geometry. Recently good Si1-xGex gradient crystals of sufficiently large size have been grown by means of the Czochralski technique with geranium content x between 0.02 and 0.08. We find peak reflectivities of these crystals of up to 96%, accompanied by a large increase of the FWHM of the reflection. Combining these properties and the principle of the comb structure, the intensity gain should be easily increasable to factor of 1600 as compared to a set-up with perfect single-crystal monochromator and analyzer.

Laterally graded Si1-xGex crystals for high-resolution synchrotron x-ray optics

We present first experimental data on a novel type of optical element for synchrotron radiation applications in the x-ray region: namely laterally-graded aperiodic crystals on the basis of Si1-xGex alloys. The lattice parameter of such a gradient crystal containing up to some atomic % Ge in a Si single crystal changes nearly linearly along the plate of diffraction. Thus the variation of the Bragg angle of divergent incident light on the crystal can be compensated for. This opens up the possibility to operate a crystal monochromator in nearly crystal limited resolution in the whole energy range above 2 keV at the full vertical divergence without a collimating premirror. Simultaneously the reflected spectral intensity can be increased considerably as compared with a conventional Si-crystal monochromator.