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1

Digitale Medien

Lattice site location of ion-implanted 8Li in Silicon Carbide (2002)

Virdis, S. ; Vetter, U. ; Ronning, C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 91 (2002), S. 1046-1052

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The lattice sites of ion-implanted Li atoms in 6H-, 4H-, and 3C-SiC were studied. Radioactive 8Li ions (t1/2=0.84 s) were implanted with 60 keV into the crystalline SiC samples, and the channeling and blocking effects of 1.6 MeV alpha particles emitted in the decay were measured to determine the Li lattice sites. The alpha emission channeling spectra measured along different crystallographic directions reveal that Li occupies mainly interstitial sites with tetrahedral symmetry, centered along the c-axis atom rows in the hexagonal lattices. In the cubic 3C-SiC structure, Li is located on tetrahedral interstitial sites as well. For 6H-SiC, the implantation temperature was varied between 200 and 823 K without observing significant changes in the emission channeling spectra. Thus, Li diffusion or Li defect interaction resulting in a lattice site change does not occur in this temperature regime. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1425442

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2

Digitale Medien

Ion beam deposition of fluorinated amorphous carbon (2001)

Ronning, C. ; Büttner, M. ; Vetter, U. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 90 (2001), S. 4237-4245

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We have studied the growth and the properties of (t)a-C:F films prepared by the deposition of mass separated 12C+ and 19F+ ions as a function of the F concentration. The films are always strongly F deficient due to the formation of volatile F2 and CFx molecules during the deposition process. A maximum F content of about 25 at. % is obtained for an ion charge ratio of C+:F+=1:1. The observed mechanical, optical, electrical, and structural properties as well as the thermal stability of the films are strongly influenced by the F content. A three step progression of the film structure is evident for increasing F concentration: the amorphous three-dimensional network of tetrahedrally bonded carbon atoms of pure carbon films (ta-C) with diamondlike properties is doped for very low F concentrations (ta-C:F). A further increase of the F content results first in transformation to a graphitelike amorphous structure (a-C:F) before the deposited films become porous and to a polymerlike one for the highest F content. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1404419

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3

Digitale Medien

Ion implanted dopants in GaN and AlN: Lattice sites, annealing behavior, and defect recovery (2000)

Ronning, C. ; Dalmer, M. ; Uhrmacher, M. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 87 (2000), S. 2149-2157

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The recovery of structural defects in gallium nitride (GaN) and aluminum nitride (AlN) after implantation of 111In+ and 89Sr+ in the dose range (0.1–3) 1013 cm−2 and ion energies of 60–400 keV has been investigated as a function of annealing temperature with emission channeling (EC) and perturbed γγ angular correlation spectroscopy. The implanted In and Sr atoms occupied substitutional sites in heavily perturbed surroundings of point defects after room temperature implantation. No amorphization of the lattice structure was observed. The point defects could be partly removed after annealing to 1473 K for 10–30 min. Lattice site occupation of implanted light alkalis, 24Na+ in GaN and AlN as well as 8Li+ in AlN, were also determined by EC as a function of implantation and annealing temperature. These atoms occupied mainly interstitial sites at room temperature. Lithium diffusion and the occupation of substitutional sites was observed in GaN and AlN at implantation temperatures above 700 K. A lattice site change was also observed for sodium in AlN, but not in GaN after annealing to 1073 K for 10 min. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.372154

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4

Digitale Medien

Inheritance of the sesquiterpenes longipinenone and hydroxy-longipinenone within the Achillea millefolium complex (Compositae) (2001)

Fischer, U. ; Vetter, S. ; Novak, J. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

Plant breeding 120 (2001), S. 0

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ISSN: 1439-0523

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft

Notizen: Three selfing and 13 crossing experiments between tetraploid individuals of Achillea ceretanica, Achillea collina, Achillea distans ssp.‘styriaca’ Saukel (ined.), and Achillea pratensis (Achillea millefolium complex, Compositae), five F1 crosses, three backcrosses and one further selfing experiment were carried out in order to study the inheritance of longipinenone (1) and its hydroxyl derivative (2). From these crossings, 1294 plants were studied by qualitative thin layer chromatography. Progenies from parent and F1 plants without longipinenones (0-type, ll) uniformly contained none of these two sesquiterpenes. All other crossing experiments showed typical segregation patterns of 0-type, L-type (longipinenone (1) without hydroxylongipinenone, L.hh) and H-type (hydroxy-longipinenone (2) and occasionally longipinenone, L.H.) in the ratio of 1 : 1 and 1 : 3. According to these results both derivatives are under dominant genetic control regulated by genes L and H, whereby hydroxylation takes place after synthesis of longipinenone (1).

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1046/j.1439-0523.2001.00603.x

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5

Digitale Medien

The Sc+NO→ScO+N reaction: Rotational state distribution in ScOX 2Σ+(v″=0) (2001)

Luc, P. ; Vetter, R.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 115 (2001), S. 11106-11117

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The Sc+NO→ScO+N reaction has been investigated in a beam-gas arrangement, with characterization of ScO products by cw laser-induced fluorescence: absorption versus laser frequency over the A 2Π(v′=1)–X 2Σ+(v″=0) band and fluorescence over the A 2Π(v′=1)–X 2Σ+(v″=1) one. It leads to the direct determination of the nascent rotational state distribution in the X 2Σ+(v″=0) level of ScO. This distribution is close to a Prior statistical one, with a well-characterized weak "surprisal," indicating that a momentum constraint takes place during the reaction process. In the frame of this statistical distribution, a new accurate value for the dissociation energy of ScO is proposed: D00(ScO)=(6.92±0.01) eV. Spectroscopic data are reported for the A 2Π(v′=1)–X 2Σ+(v=0) band, up to N=98. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1421072

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6

Digitale Medien

A full description of the potential curve of the B 1Πu state of 7Li2 (2001)

Bouloufa, N. ; Cacciani, P. ; Vetter, R. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 114 (2001), S. 8445-8458

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: An accurate potential curve for the bound and quasibound region of the B 1Πu state of 7Li2 is produced by analyzing high resolution sub-Doppler B 1Πu←X 1Σg+ excitation spectra in conjunction with lower resolution data of Hessel and Vidal [J. Chem. Phys. 70, 4439 (1979)] and of Russier et al. [J. Mol. Spectrosc. 168, 39 (1994)]. The bound and quasibound part of the curve is generated by the direct fit of molecular energies to a numerical potential; the outermost (repulsive) part of the curve is calculated by an asymptotic method using Coulombic and exchange parameters determined from the 1 1Πg and A 1Σu+ states of the lithium dimer. The full potential energy curve of the B 1Πu state reproduces all measured energies of f parity, and the widths of the predissociated lines, to within the experimental accuracy. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1364687

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7

Digitale Medien

Pacemaker Therapy in Isolated Congenital Complete Atrioventricular Block (2002)

BREUR, JOHANNES M.P.J. ; UDINK Ten Cate, FLORIS E.A. ; KAPUSTA, LIVIA ; [weitere]

Oxford, UK : Blackwell Futura Publishing, Inc.

Pacing and clinical electrophysiology 25 (2002), S. 0

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ISSN: 1540-8159

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Medizin

Notizen: BREUR, J.M.P.J., et al.: Pacemaker Therapy in Isolated Congenital Complete Atrioventricular Block. The aim of this study was to evaluate the effect of pacemaker (PM) therapy in patients with isolated congenital complete atrioventricular block (CCAVB). Patients with CCAVB eventually qualify for PM implantation, however, timing remains controversial. Retrospective evaluation of left ventricular end-diastolic diameter (LVEDD), shortening fraction (SF), and cardiothoracic ratio (CTR) in 149 CCAVB patients, before, at, and after PM implantation was carried out. LVEDD shows an average increase of 0.48%/month in non-PM patients, and an average decrease of 0.88%/month in PM patients. SF shows an average increase of 0.10%/month in non-PM, and an average decrease of 0.32%/month in PM patients. CTR shows an average increase of 0.02%/month in non-PM, and an average decrease of 0.19%/month in PM patients. The difference between the non-PM and PM groups is significant (P = 0.05) for all variables. Symptomatic patients show no significant change in LVEDD after PM therapy (from 66.5% before to 68.5% after PM therapy). Asymptomatic patients do show a significant (P 〈 0.001) decrease in LVEDD after PM therapy (from 78.4% before to 73.3% after PM therapy). CTR does not differ significantly between symptomatic and asymptomatic patients before PM therapy (58% and 57%, respectively). CTR does differ significantly (P 〈 0.001) between symptomatic and asymptomatic patients after PM therapy (52% and 48%, respectively). Heart size and SF are increased in most patients with isolated CCAVB. PM implantation is associated with a decrease in heart size and normalization of SF in most patients. Indications for PM therapy in children may require reevaluation in asymptomatic patients with increased cardiac size and decreased cardiac function.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1046/j.1460-9592.2002.01685.x

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8

Digitale Medien

X-ray topographic dislocation contrast visible in reflections orthogonal to the Burgers vectors of axial screw dislocations in hexagonal silicon carbide (2001)

Vetter, W. M. ; Dudley, M.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 34 (2001), S. 20-26

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: Contrast is associated with micropipes in X-ray topographs of SiC crystals obtained with prismatic reflections, representing an apparent violation of the g·b = 0 invisibility criterion. This is explained as a population of basal-plane dislocations with Burgers vectors of the set b = {\textstyle{1 \over 3}}〈11{\bar{2}}0〉 that occur in a high density within a few micrometers of the micropipes, below the resolution of X-ray topography. These basal-plane dislocations could be observed under an electron microscope. The presence of the surfaces of the micropipes influences the dislocation images in the topographs taken with prismatic reflections, often resulting in a band of light contrast along the axes of the micropipes.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889800017027

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