M. Lefeld-Sosnowska

Magnetic and optical properties of GaMnN magnetic semiconductor

Microcrystalline Ga1−xMnxN samples with Mn content up to x=0.005 were grown by an ammonothermal method and were studied using various techniques. X-ray diffraction showed characteristic diffraction lines for hexagonal GaN phase mixed with a small contribution (<5%) from the Mn3N2 phase. Raman spectra exhibited characteristic peaks of pure GaN and modes that could be associated with Mn-induced lattice disorder. Electron spin resonance and magnetization measurements were consistent with the dominant Mn2+(d5) configuration of spin S=5/2 which is responsible for the observed paramagnetic behavior of the GaMnN material.

Extended defects in GaN single crystals

GaN single crystals grown by the high-pressure/high-temperature method were investigated by x-ray diffractometry and projection topography methods. The grown-in extended defects - low-angle grain boundary, straight dislocations of directions correlated to the growing lattice planes and large defects (probably inclusions) - were for the first time observed and investigated by x-ray projection topography.

A study of defects generated in Czochralski-grown Si during two-step annealing

A variety of oxygen-related micro-defects (spherical and octahedral precipitates, their agglomerations, dislocations and dislocation loops) with dimensions in the range 0.1-100 mu m were revealed using X-ray topography and transmission electron microscopy after two-step annealing of Czochralski-grown silicon. The defects are distributed in a non-uniform way across the samples with the gradient of their density normal to the crystal surface.

Bragg-case section topography of growth defects in Si : Ge crystals

The samples cut out from Si : Ge crystals with 3% and 1.2% of germanium were studied by means of synchrotron white beam Bragg-case section and projection topography as well as conventional transmission Lang topography. The obtained topographs revealed dominant contrast coming from the segregation of germanium. The use of Bragg-case section topography made possible to follow the shape of growth surfaces inside the crystal. The formation of contrast in Bragg-case section topographs for different orientation of growth surfaces with respect to the incident beam is discussed. The applied methods enabled also revealing growth surface instabilities occurring in some regions of Si : Ge crystals.

Study of Extended Defect Structure Induced by Pulsed Laser Annealing in Implanted Silicon Crystals

(a) Institute of Physics, Polish Academy of Sciences, Al. Lotniko´w 32/46,PL-02-668 Warsaw, Poland(b) Institute of Experimental Physics, Warsaw University, Ul. Hoz˙a 69,PL-00-681 Warsaw, Poland(c) Institute of Electron Technology, Al. Lotniko´w 32/46, PL-02-668 Warsaw, Poland(Received October 1, 1998)An analysis of extended defects generated during annealing by pulsed excimer laser radiation in sili-con crystals implanted with Ge ions is presented. The investigation was performed by means of twocomplementary methods: the interference-polarizing microscopy and the Lang X-ray transmissiontopography. The existence of extended defects was revealed. It has been stated that the distributionof these defects depends on the distribution of the power density in the laser beam cross-section.

Extended defect structure induced by pulsed laser annealing in Ge implanted Si crystal

The study of extended defects structure induced by the pulsed nanosecond radiation of an excimer laser with different energy density in Si single crystal implanted with Ge ions. Numerical calculations were done to determine the optimal value of the laser energy density causing the epitaxial recrystallization from the melt on a crystal substrate. The RBS were performed to study the near-surface structure of the different areas of the sample. The surface morphology was observed using the interference-polarizing microscope. Through the application of the section X-ray topography we have observed the crystal lattice deformation caused by laser annealing.

Contrast in transmission X-ray diffraction topographs of growth defects in the core of SrLaGaO4 single crystals

Defects in the core of SrLaGaO4 single crystals, grown by the Czochralski method using a [001]-oriented seed, were studied by transmission X-ray diffraction projection topography. Topographs were taken with radiation from a laboratory source and with high-energy radiation available at the ESRF beamline ID19 in Grenoble. The contrast of the investigated defect images was analysed for various diffraction vectors g and for various values of the product μ0t (μ0 is the linear absorption coefficient and t the crystal thickness). This allowed the contrast formation to be studied as a function of absorption. The results of the analysis confirm the model of crystal lattice deformation around rod-like volume defects in SrLaGaO4 crystals.

X-ray topography studies of microdefects in silicon

X–ray topography has been successfully applied to study microdefects with the sizes in the range from well below standard topographic resolution to tenths of micrometers, thus effectively widening applicability of the Lang section topography. The lower value is set by the application of high order asymmetric reflection. Disappearance of the Kato fringes on the section topography is a clear indication of the existence of defects, which are otherwise not detectable as the standard contrast features. The presence of the defects with such sizes was also confirmed by transmission electron microscopy. Microdefects in the higher end of the size spectrum are well covered by Lang traverse and section topography where detailed contrast study is possible for individual defects. Lang traverse and section topography was applied to study specific case of oxygen related defects in silicon crystals.

X-ray topographic study of defects in annealed silicon

X-ray topography was applied to characterize defects in silicon subjected to thermal treatments. In one group of Czochralski-grown (CZ) samples numerous precipitates and dislocation loops were generated by making scratches with metallic contaminants (Ni, Fe, Cu) on one surface. Rapid thermal annealing (RTA) was performed at 1150 degrees C for 300 s in an oxidation atmosphere. Far away from the damaged regions no structural defects were detected in any of the samples. In other CZ samples small precipitates of nonuniform density were produced after two-step annealing (TSA) at 900 degrees C (for 75 min) and 1150 degrees C (for 8 h) in an oxygen atmosphere.

Studies of growth bands in Si:Ge crystals

Si:Ge crystals with approximately 3% of germanium were studied with various topographic methods using both conventional and synchrotron sources of X-rays. The present investigation included various types of white beam synchrotron topography and conventional Lang topographic methods. The topographic results obtained with various methods were dominated by strong contrast coming from growth bands. The Bragg-case section topographs with the beam front limited to 5 μm revealed the distribution of growth bands inside the crystals. Thanks to the low glancing angle the section topographs provided many information about the shape of growth surface despite small thickness of investigated wafers. Additionally taking the topographs at very large film-to-crystal distances it was possible to reveal the character of lattice deformation across the striations and to draw information about germanium distribution.