Search results

1

X-ray Standing Waves and Rutherford backscattering Studies of the Structure of Si Single Crystals Implanted with Fe Ions

100%

Vartanyantz I., Auleytner J., Nowicki L., Kwiatkowski S., Turos A.

Acta Physica Polonica A

|

1996

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vol. 89

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issue 5-6

625-633

EN

The X-ray standing wave and Rutherford backscattering spectroscopy in channelling geometry were applied for the investigation of the structure of silicon single crystals implanted with 80 keV Fe ions. Both methods were used for the determination of crystal damage and lattice location of implanted metal atoms before and after thermal annealing. Both methods gave consistent results regarding the amorphization of Si due to the Fe-ion implantation. Moreover, using both methods some Fe substitution fraction was determined. The depth profiles of implanted atoms were compared to the results of computer simulations. Complementary use of X-ray standing wave and Rutherford backscattering spectroscopy channelling techniques for studies of radiation damage and lattice location of implanted atoms is discussed.

2

Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

100%

Wierzchowski W., Mazur K., Strupiński W., Wieteska K., Graeff W.

Acta Physica Polonica A

|

1996

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vol. 89

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issue 3

341-346

EN

The formation of misfit dislocation was studied in GaAs homoepitaxial layers on the substrates containing considerable amount of isoelectronic indium. The layers were grown with metal-oxide chemical vapour deposition and chemical vapour deposition methods including low temperature process with tertiarbutylarsine arsenic source. The critical conditions of misfit dislocation formation were exceeded up to 5×. The samples were examined before and after epitaxial process with a number of different X-ray topographic and diffractometric methods, including high resolution synchrotron white beam topography. The crystallographic identification of the defects was supported by the numerical simulation of topographic images. It was found that a number of threading dislocations, continuing in the epitaxial layer from those existing in the substrate, did not take part in the formation of misfit dislocations despite a suitable slip system. On the other hand, the formation of misfit dislocations from small imperfections of epitaxial deposit was proved in many cases. A reasonable good quality of the layers was confirmed by the resolution of individual defects and only small broadening of rocking curves.

3

X-Ray Standing Wave Technique as a Tool in the Study of the Imperfect Crystals

100%

Pełka J., Auleytner J.

Acta Physica Polonica A

|

1992

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vol. 82

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issue 1

163-171

EN

The application of the X-ray standing wave (XSW) technique in the case of imperfect crystals meets serious theoretical and interpretational problems. However, well-known advantages of the XSW technique make it especially interesting to the study of the ordering of impurities and of various processes leading to changes in this ordering in various likes of imperfect crystals. In this work we try to answer the question how imperfection of a crystal may influence the changes in fluorescence yield during the XSW measurement. Two likes of imperfect crystals are studied: Si(111) implanted with high energetic Bi^{+} ions, and Zn_{1-x}Co_{x}Se single crystal with natural (111) face. The discussion of obtained results shows that general features of the X-ray standing wave field are conserved despite the considerable imperfections of the crystals. The results seem to support the applicability of the XSW technique to the study of imperfect materials, although some further theoretical effort would be required.

4

How to Distinguish Perfect Quasi-Crystals from Twins and Other Structures Using Diffraction Experiments?

100%

Wolny J.

Acta Physica Polonica A

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1992

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vol. 82

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issue 1

173-177

EN

Performing diffraction experiments for various lengths of coherent scattering and using the scaling of peak intensities on a number of atoms one can experimentally distinguish quasi-crystals from the other structures (e.g. twins or random). For perfect quasi-crystals peak intensities scale as N^{2}, for other structures this scaling depends on concentration of atoms, behaving critical for Penrose concentration.

5

Stereoscopic Observation of Synthetic Diamond with Haruta Stereo-Pairs of Synchrotron Transmission Double-Crystal Topographs

100%

Moore M., Lang A. R., Wierzchowski W.

Acta Physica Polonica A

|

1994

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vol. 86

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issue 4

613-616

EN

The Haruta method is used for stereoscopic observation of a 1.5 × 4 × 4 mm^{3} cuboctahedral synthetic diamond with transmission double-crystal topography. The experiments were performed using a synchrotron double-crystal arrangement with asymmetrical diamond 220 reflection selecting 1.0 Å radiation. The appropriate Haruta pairs were matched from a series taken with positions on the rocking curve changed by small intervals. A reasonable stereoscopic effect was observed for most defect images, particularly dislocations, stacking faults and growth sector boundaries. It was established that some interference fringes do not produce good stereoscopic effects and appear on the exit surfaces of the diamond.

6

X-Ray Topographic Investigation of Cellular Structure and its Relation to another Defects in Various Types of GaAs Single-Crystals

100%

Wierzchowski W., Mazur K.

Acta Physica Polonica A

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1993

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vol. 84

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issue 4

789-794

EN

The defect patterns in GaAs crystal grown using liquid encapsulated Czochralski and gradient freeze methods with various types of doping were characterized using complementary X-ray topographic methods. It was found that the cellular structure occurring in the low doped crystal is developed independently from the actual growth surface. The occurrence of the cellular structure is connected with significant lattice deformation, and some results point that significant stress can influence its formation. The high doping prevents formation of the cellular structure, but at higher doping the phenomenon of "cellular growth" can occur due to instabilities of the growth surface. The present results point that defect pattern in GaAs crystals is more affected by the type of doping than by the choice of the growth method.

7

Synchrotron White Beam Topographic Studies of Gallium Arsenide Crystals

100%

Wierzchowski W., Wieteska K., Graeff W.

Acta Physica Polonica A

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1997

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vol. 91

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issue 5

1015-1019

EN

A series of samples cut out from different types of gallium arsenide crystals with low dislocation density were studied by means of white beam synchrotron topography. The investigation was performed with transmission and back-reflection projection methods and transmission section method. Some of the topographs in transmission geometry provided a very high sensitivity suitable for revealing small precipitates. The transmission section images significantly differed depending on the wavelength and absorption. In some cases a distinct Pendellösung fringes and fine details of dislocation and precipitates images were observed. It was possible to reproduce the character of these images by means of numerical simulation based on integration of Takagi-Taupin equations. Due to more convenient choice of radiation, synchrotron back-reflection projection topography provided much better visibility of dislocations than analogous methods realized with conventional X-ray sources.

8

High-Temperature X-ray Diffraction Studies of Lattice Dynamics in Ni_{3}(Fe,Nb) Ordered Alloys

100%

Mekhrabov A.

Acta Physica Polonica A

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1994

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vol. 85

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issue 3

571-578

EN

A study is performed on characteristics of lattice dynamics in the initially ordered ternary Ni_{3}(Fe_{1-x}Nb_{x}) (x = O to 10 at.%) alloys using high temperature X-ray diffractometry for the temperature range from 300 K to 1300 K. Aspects investigated included temperature and concentration dependencies of the full mean square atomic displacements Ū²_{f}, the Debye characteristic temperature Θ_{D}, and linear thermal expansion coefficient α. It is found that the Ū²_{f}, Θ_{D}, and α parameters show anomalous change at temperatures where the alloys are subjected to order-disorder phase transitions. It is further found that Nb addition results in the considerable increase in the parameters Ū²_{f} and α and decrease in Θ_{D}. Moreover, the addition of Nb stabilizes Ni_{3}Fe ordered structure and shifts the order-disorder transition to higher temperature.

9

Lattice Deformation in Al_{x}Ga_{1-x}As Epitaxial Layers Caused by Implantation with High Doses of 1 Mev Si Ions

63%

Wieteska K., Wierzchowski W., Graeff W., Turos A., Grötzschel R.

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vol. 96

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issue 2

289-293

EN

A series of highly perfect Al_{0.45}Ga_{0.55} As epitaxial layers implanted with 1 MeV Si ions to the doses in a range 7×10^{13}-2×10^{15} ions/cm^{2} were studied with various conventional and synchrotron X-ray diffraction methods. The presently used methods allowed both the measurement of lattice parameter changes and strain induced deformation. The evaluation of complete strain profiles was also performed by numerical simulation of diffraction curves. It was found that the implantation induced considerable change of lattice parameter reached the maximum at the dose 3×10^{14} ions/cm^{2}. The recorded curves proved also that the lattice parameter is almost constant in the near surface region of the implanted layers. The applied doses did not cause lattice amorphisation at room temperature.

10

Investigation of Near Surface Distortions in Si Single Crystals by Means of Spatial Distribution Analysis of Reflected Beams

63%

Khrupa V., Krasulya S., Machulin V., Datsenko L., Auleytner J.

Acta Physica Polonica A

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1996

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vol. 89

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issue 3

309-313

EN

A diffractometrical method for quantitative evaluation of structure perfection level in silicon single crystals containing various types of near surface distortions is described. The method is based on the spatial distribution analysis of the reflected intensity in the Bragg case of diffraction. To implement the proposed approach one has to satisfy the condition of the so-called low X-ray absorption because in this case the penetration depth of diffracted radiation exceeds the corresponding value of extinction length. It permits us to obtain a remarkable value of noncoherent reflectivity due to defects placed in deep (on the extension of absorption length) regions of a crystal and therefore, to increase the sensitivity of scattering for low distortions of crystal lattice. Using the method described here the extension of various disturbed layers as well as the level of the static Debye-Waller factor of a crystal can be determined. The effect of surface distortions caused by mechanical treatment and the influence of the following thermal annealing as well as irradiation by high energy protons on the defective structure of the samples were investigated.

11

Investigation of Morphology and Chemical Composition of Self-Organized Semiconductor Quantum Dots and Wires by X-Ray Scattering

63%

Holý V., Meduňa M., Stangl J., Roch T., Bauer G.

Acta Physica Polonica A

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2002

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vol. 102

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issue 1

7-19

EN

X-ray scattering methods suitable for the investigation of the morphology and chemical composition of self-organized quantum dots and quantum wires are reviewed. Their application is demonstrated in experimental examples showing that a combination of small angle X-ray scattering with high-resolution X-ray diffraction can reveal both the shape and the chemical composition of the self-organized objects.

12

Interpretation of Differential Anomalous X-Ray Scattering Data for Amorphous Cd-As

63%

Burian A., Lecante P., Mosset A., Galy J., Tonnerre J. M., Raoux D.

Acta Physica Polonica A

|

1994

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vol. 86

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issue 4

633-640

EN

The computational procedure, based on Warren's exact method for an amorphous sample with more than one atom, was developed to obtain the short-range order structural parameters from the differential anomalous X-ray scattering data, collected using the synchrotron radiation. The experimental differential radial distribution functions were fitted with the true distribution functions expressed in an analytical form and broadened by convolution with the pair functions. It was found that atoms in the amorphous Cd-As films remain almost tetrahedrally coordinated and the investigated alloys are chemically ordered.

13

Process of Amorphization Induced by Mechanical Alloying of Iron with Tungsten and Niobium

63%

Jartych E., Oleszak D., Żurawicz J.

Acta Physica Polonica A

|

2001

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vol. 100

|

issue 5

731-736

EN

Mechanical alloying method was used to synthesise powders of iron with tungsten and niobium. Mössbauer spectroscopy and X-ray diffraction have been applied to monitor the progress in solid-state reactions. In the case of Fe-W system, exhibiting a positive heat of mixing, no trace of amorphization was observed for 20 and 33 at.% of W, as the calculations of phase diagram (CALPHAD) method suggest. During the mechanical alloying process, two solid solutions Fe(W) and W(Fe) were obtained. Mössbauer measurements allowed to recognise the Fe(W) solid solution as a ferromagnetic phase, while the W(Fe) solid solution as a paramagnetic one. In the case of Fe-Nb system, exhibiting a negative heat of mixing, single phase amorphous alloys were synthesised during mechanical alloying of iron with 48 and 64 at.% of Nb. For both investigated compositions, the final products of mechanical alloying processes were amorphous paramagnetic alloys.

14

Effect of Uniaxial Stretching on Structural Properties of Poly(3-Alkylthiophenes)

63%

Łużny W., Zagórska M.

Acta Physica Polonica A

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1997

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vol. 92

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issue 3

491-500

EN

The influence of uniaxial stretching on the molecular structure of poly(3-alkylthiophenes) was studied with the use of X-ray diffraction. Three poly(3-alkylthiophenes), namely these containing n-hexyl, n-octyl and n-decyl groups, were investigated. The samples were oriented by stretching and the diffraction patterns for two geometries of scattering were obtained for undoped samples. The comparison of experimental diffraction data for unoriented and oriented samples, gives information about the role of the side chains in the changes of molecular conformation induced by stretching of the polymer sample. The main conclusion of our work is that the process of orientation induces similar phenomena in all samples studied, but the structural and conformation changes depend on the side chain length: the shorter the alkyl substituent, the easier the straightening of the main polymer chain. The authors suggest that uniaxial stretching of poly(3-alkylthiophenes) changes the degree of main chain planarity. This effect can influence the π-conjugation in polymer system, which may have great importance for any future application of poly(3-alkylthiophenes).

15

X-ray Standing Wave Studies of Si (111) Crystal Implanted by Fe and Ni Ions

63%

Vartanjantz I., Kovalchuk M., Sosphenov A., Auleytner J., Majewski J.

Acta Physica Polonica A

|

1991

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vol. 80

|

issue 6

811-817

EN

The X-Ray Standing Wave Method (XRSW) was applied for the investigation of the silicon samples implanted with 80 keV Fe and Ni ions. The samples were measured by the XRSW method before and after annealing process. For theoretical calculations the two layer model was used. The analysis revealed that after annealing only a slight amount (~20÷30%) of the implanted atoms occupy the position of the Si crystal planes. The Rutherford backscattering (RBS) experiment that confirms the results obtained by the XRSW method was performed.

16

Single-Crystal X-Ray Diffractometry Using Synchrotron Radiation

63%

Eichhorn K.

Acta Physica Polonica A

|

1992

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vol. 82

|

issue 1

51-65

EN

The properties of synchrotron radiation relevant to single-crystal X-ray diffractometry are: its high intensity over a wide spectral range, a small source size and a low divergence in the 0.1 mrad range, about 90% linear polarization in the horizontal plane, a pulsed time structure, and a time dependent intensity. The latter property requires monitoring of the primary beam intensity and its polarization state which slightly complicates data collection and needs particular attention in the data reduction stage. The other properties of synchrotron radiation, however, extend the range of X-ray diffractometry to experiments which are not feasable with sealed X-ray tubes. The high source intensity makes data collection possible on crystals down to and below 10 μm diameter. Measurement of weak and very weak ("forbidden") reflections profits from high intensity, low divergence, and a good peak-to-background ratio. Data collection at short wavelengths is useful to decrease both absorption and extinction effects and provides the resolution required for high precision structure analysis. Wavelength tun-ability is frequently used to exploit resonant X-ray scattering ("anomalous dispersion") for structure research. Examples are determination of absolute configuration, contrast variation, and phase determination from both single-and multiple-wavelength measurements ("MAD-phasing"). X-ray dichroism and double refraction are observed in the vicinity of absorption edges, causing an anisotropy and polarization dependence of anomalous scattering. This anisotropy may give rise to a violation of extinction rules for glide-planes and screw-axes, with orientation- and polarization-dependent intensities. More recently, these affects have been successfully used to derive (partial) phase information. Other applications are magnetic X-ray scattering and time-resolved X-ray diffraction, the latter exploiting the time structure of the synchrotron radiation source.

17

Lattice Deformation Studies in Silicon Implanted with High-Energy Protons

63%

Wieteska K., Dłużewska K., Wierzchowski W.

Acta Physica Polonica A

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1996

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vol. 89

|

issue 3

395-400

EN

The deformation of crystal lattice in silicon implanted with protons of energy 1.6-9 MeV was studied by means of X-ray topography and double-crystal rocking curve measurements. The samples were investigated as-implanted and after thermal and electron annealing. The surface relief of the implanted part of the crystal was also revealed with optical methods. As-implanted wafers exhibited spherical bending being convex at the implanted side. Thermal and electron annealing caused a dramatic increase in bending of the implanted part while the bending of the remaining part of the sample was reduced. A characteristic behaviour of a double-crystal topographic contrast in the annealed crystals was explained due to bending of the shot-through layer along the Gaussian profile.

18

Structural Characterization of Carane Derivative Stereoisomers - Potent Local Anesthetics

63%

Grochowski J., Serda P., Pasenkiewicz-Gierula M., Czarnecki R., Librowski T., Lochyński S., Frąckowiak B.

Acta Physica Polonica A

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2002

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vol. 101

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issue 5

665-674

EN

The paper reports on structural investigation and phase analysis of a newly synthesized potent local anesthetic with chiral molecular structure. Absolute structure and absolute configuration on four chiral centres was determined using microcrystalline single-crystal diffraction with anomalous scattering of X-ray radiation azimuthal scan technique. Phase analysis for new compound (KP23SS) and its epimer (KP23RS) was carried out using classical and synchrotron radiation powder diffraction. Enantiopurity of the bulk material was verified for both isomers by comparison of experimental and simulated high-resolution powder diffraction diagrams. The presence of two new polymorphic phases of KP23RS was documented. Comparative conformational analysis was carried out using differential Fourier synthesis and least-squares molecule overlap technique. A model of epimeric disorder was discussed for the homochiral phase.

19

Application of Third Generation Synchrotron Source to Studies of Non-Crystalline Materials: In-Se Amorphous Films

63%

Burian A., Jabłońska A., Burian A., Le Bolloc'h D., Metzger H., Proux O., Hazemann J., Mosset A., Raoux D.

Acta Physica Polonica A

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2002

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vol. 101

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issue 5

701-708

EN

The local structure of vacuum evaporated In-Se amorphous films, containing 50, 60, and 66 at.% Se, was studied using differential anomalous X-ray scattering and extended X-ray absorption fine structure. Both intensity and absorption spectra were measured in the vicinity of the absorption K-edge of Se. The differential anomalous X-ray scattering data were converted to real space by the inverse Fourier transform yielding the differential radial distribution functions. The obtained results provide evidence for the presence of Se-In spatial correlations for In_{50}Se_{50} and Se-In and Se-Se correlations for In_{40}Se_{60} and In_{34}Se_{66} within the first coordination sphere.

20

Observation of Interference Fringes in Bragg-Case Synchrotron Double-Crystal Images of Stacking Faults in Diamond

63%

Wierzchowski W., Moore M.

Acta Physica Polonica A

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1992

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vol. 82

|

issue 2

185-191

EN

Bragg-case synchrotron double-crystal images of stacking faults were studied in a slab prepared from a synthetic diamond of a good quality. The images of stacking faults in topographs taken on the tails of the rocking curve exhibited well pronounced interference fringes. The fringes were strongly dependent on the angular setting and they were less spaced further from the maximum. The experimental images were compared with those theoretically predicted from an application of plane-wave dynamical theory. A reasonably good correspondence between theoretical and experimental images was obtained. The theoretical images of stacking faults were dependent on the type of stacking fault, producing some difference in the first fringe.

Refine search results

X-ray Standing Waves and Rutherford backscattering Studies of the Structure of Si Single Crystals Implanted with Fe Ions

Investigation of Misfit Dislocation Sources in GaAs Epitaxial Layers

X-Ray Standing Wave Technique as a Tool in the Study of the Imperfect Crystals

How to Distinguish Perfect Quasi-Crystals from Twins and Other Structures Using Diffraction Experiments?

Stereoscopic Observation of Synthetic Diamond with Haruta Stereo-Pairs of Synchrotron Transmission Double-Crystal Topographs

X-Ray Topographic Investigation of Cellular Structure and its Relation to another Defects in Various Types of GaAs Single-Crystals

Synchrotron White Beam Topographic Studies of Gallium Arsenide Crystals

High-Temperature X-ray Diffraction Studies of Lattice Dynamics in Ni_{3}(Fe,Nb) Ordered Alloys

Lattice Deformation in Al_{x}Ga_{1-x}As Epitaxial Layers Caused by Implantation with High Doses of 1 Mev Si Ions

Investigation of Near Surface Distortions in Si Single Crystals by Means of Spatial Distribution Analysis of Reflected Beams

Investigation of Morphology and Chemical Composition of Self-Organized Semiconductor Quantum Dots and Wires by X-Ray Scattering

Interpretation of Differential Anomalous X-Ray Scattering Data for Amorphous Cd-As

Process of Amorphization Induced by Mechanical Alloying of Iron with Tungsten and Niobium

Effect of Uniaxial Stretching on Structural Properties of Poly(3-Alkylthiophenes)

X-ray Standing Wave Studies of Si (111) Crystal Implanted by Fe and Ni Ions

Single-Crystal X-Ray Diffractometry Using Synchrotron Radiation

Lattice Deformation Studies in Silicon Implanted with High-Energy Protons

Structural Characterization of Carane Derivative Stereoisomers - Potent Local Anesthetics

Application of Third Generation Synchrotron Source to Studies of Non-Crystalline Materials: In-Se Amorphous Films

Observation of Interference Fringes in Bragg-Case Synchrotron Double-Crystal Images of Stacking Faults in Diamond