ZfN: Search Results

1	Author	FrancisJ. Bartis	Requires cookie*
	Title
	Abstract	This problem is reconsidered in the light of the mounting evidence that dislocations act as the centres of nucleation and growth. A new relation between the fraction of the sample in liquid form and the equilibrium temperature is derived and found to fit well the data on succinonitrile and N-p-ethoxybenzylidene-p'-butylaniline (EBBA). It is argued that the additional dislocations in a cyclopentyl-l-thiaethane sample after rapid crystallization are responsible for the greater breadth of its melting transition compared to that of the same sample following slow crystallization. Past studies of the fractional melting process are criticized for their failure to include the early stages of the transition in their comparison of theory and experiment. C o u r s e o f th e M e ltin g T r a n s itio n in O r g a n ic C o m p o u n d s
	Reference	Z. Naturforsch. 46a, 630—634 (1991); received March 31 1990
	Published	1991
	Keywords	Melting, Latent heat, Organic compounds, Dislocations, Impurities
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	TEI-XML for	default:Reihe_A/46/ZNA-1991-46a-0630.pdf
	Identifier	ZNA-1991-46a-0630
	Volume	46

2	Author	StadeS. Nunes, S. Sulaiman, N. Sahoo, T. P. Das, M. Frank, W. Kreische, K. B. Nielsen	Requires cookie*
	Title	Study of the Location of Implanted Fluorine Atoms in Silicon and Germanium through Their Nuclear Quadrupole Interactions
	Abstract	Time Differential Perturbed Angular Distribution (TDPAD) measurements of the nuclear quadrupole hyperfine parameters for 19 F* implanted into amorphous, polycrystalline and crys-talline silicon and germanium are reported and reviewed. Two signals are observed in the crystalline materials (« 35 and 23 MHz in silicon, % 33 and 27 MHz in germanium) while only one is detected in the amorphous and polycrystalline samples (ä22 MHz in silicon, «27 in germanium). Impurity sites in these materials were modeled using a Hartree-Fock cluster procedure. The Intrabond, Antibond, and Substitutional sites in the bulk were studied in both silicon and germanium. The ATOP and Intrabond Surface sites were also studied in silicon and the results extended to germa-nium. Lattice relaxation effects were incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The electronic wave functions were obtained for each optimized cluster by applying Unresctricted Hartree-Fock theory, and these wave functions were used to calculate the nuclear quadrupole hyperfine parameters at the site of the fluorine nucleus. Comparison of the theoretical hyperfine parameters to the experimental values indicates that 19 F* located in the Intrabond and Intrabond surface sites could readily explain the higher frequency signal that has been observed. 19 F* in the Antibond and the surface ATOP sites yield hyperfine parameters consistent with the low frequency signal observed in the crystalline materials and the single signal observed in the amorphous (or polycrystalline) materials. Examina-tion of these two sites, in view of other available experimental evidence including the temperature dependence of the TDPAD signals, leads to the conclusion that the lower frequency signal is due to 19 F* implants which have come to rest at the site of dangling bonds in the bulk. These dangling bonds are created as a result of damage generated in the individual collision cascades during the implantation process.
	Reference	Z. Naturforsch. 51a, 560—564 (1996); received December 12 1995
	Published	1996
	Keywords	Semiconductors, Impurities, Electronic structure, Hartree-Fock, Electric field gradient
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	TEI-XML for	default:Reihe_A/51/ZNA-1996-51a-0560.pdf
	Identifier	ZNA-1996-51a-0560
	Volume	51

3	Author	F. Köksal, İ. Kartal, B. Karabulut	Requires cookie*
	Title	Electron Paramagnetic Resonance of Cu 2+ in KHC0 3 Single Crystals
	Abstract	The electron paramagnetic resonance spectra of Cu 2+ doped KHC0 3 single crystals were studied at room temperature. The results indicate a substitutional entrance of the Cu 2+ ions in place of the magnetically inequivalent K + sites. The charge compensation is supposed to be fulfilled by proton vacancies. The hyperfine lines were well resolved and the 65 Cu hyperfine coupling tensors were also found. The ground state of Cu 2+ indicates the dominance of the d x i_ y 2 orbital and, therefore, elongation of the polyhedron, similar to a lengthened octahedron.
	Reference	Z. Naturforsch. 54a, 177—179 (1999); received January 9 1999
	Published	1999
	Keywords	EPR, Cu 2+, Potassium Bicarbonate, Crystal Field, Substitution, Impurity
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	TEI-XML for	default:Reihe_A/54/ZNA-1999-54a-0177.pdf
	Identifier	ZNA-1999-54a-0177
	Volume	54

4	Author	Ho Choh, JaeKap Jung	Requires cookie*
	Title	Sung
	Abstract	External influences on the 14 N NQR of ferroelectric NaN0 2 , such as changes of the temperature, electric field, stress, gamma-ray irradiation, and impurity doping are reviewed. They normally cause either a frequency shift or a broadening of the 14 N NQR lines and are strongly related to the change of the spontaneous polarization.
	Reference	Z. Naturforsch. 55a, 124—128 (2000); received August 23 1999
	Published	2000
	Keywords	l4 N NQR, Ferroelectric NaN0 2, Spontaneous Polarization, External Effects, Impurity
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	TEI-XML for	default:Reihe_A/55/ZNA-2000-55a-0124.pdf
	Identifier	ZNA-2000-55a-0124
	Volume	55