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721 results on '"Tapfer, L"'

1. Controlled nucleation and growth of CdS nanoparticles in a polymer matrix

Author

Di Luccio, T., Laera, A. M., Tapfer, L., Kempter, S., Kraus, R., and Nickel, B.

Subjects
Condensed Matter - Materials Science
Abstract

The nucleation and growth of CdS nanoparticles within a polymer matrix was followed by in-situ synchrotron X-ray diffraction. The nanoparticles form by effect of the thermolysis of thiolate precursors at temperatures between 200 and 300 Celsius degrees. Above 240 Celsius degrees the precursor decomposition is complete and CdS nanoparticles grow in the polymer matrix forming a nanocomposite with interesting optical properties. The nanoparticle structural properties (size and crystal structure) depend on the annealing temperature.(abridged version), Comment: 25 pages, 7 figures, 1 table

Published
2006
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2. Microstructural and morphological properties of homoepitaxial (001)ZnTe layers investigated by x-ray diffuse scattering

Author

Di Luccio, T., Scalia, G., Tapfer, L., Morales, P., Traversa, M., Prete, P., and Lovergine, N.

Subjects
Condensed Matter - Materials Science
Abstract

The microstructural and morphological properties of homoepitaxial (001)ZnTe layers are investigated by x-ray diffuse scattering. High resolution reciprocal space maps recorded close to the ZnTe (004) Bragg peak show different diffuse scattering features. One kind of cross-shaped diffuse scattering streaks along <111> directions can be attributed to stacking faults within the epilayers. Another kind of cross-shaped streaks inclined at an angle of about 80deg with respect to the <110> in-plane direction arises from the morphology of the epilayers. (abridged version)

Published
2005
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3. Structural and morphological investigation of Langmuir-Blodgett SWCNT/behenic acid multilayers

Author

Di Luccio, T., Antolini, F., Aversa, P., Scalia, G., and Tapfer, L.

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

The goal of our work has been the incorporation of single wall carbon nanotubes (SWCNTs) in Langmuir-Blodgett organic multilayers. We deposited multilayers consisting of six cadmium behenate (CdBe) layers alternated with one layer of SWCNTs. SWCNTs and CdBe molecules were spread at the air/water interface and deposited at a fixed compression pressure for CdBe (27mN/m) and two different compression pressures for the nanotubes, 15 and 45mN/m, respectively. Low angle X-ray measurements exhibited distinct satellite peaks in all the samples demonstrating that the periodicity of the LB CdBe reference sample was conserved when SWCNTs were inserted in the structure. In agreement with the observations at optical and electronic microscopes, the samples deposited at the higher compression pressure (45mN/m) presented more densely-packed and more uniform coverage of nanotubes., Comment: 13 pages including 4 figures and 1 table. Carbon, in press

Published
2003

20. Secondary ion mass spectrometry and x-ray analysis of superconducting Nb/Pd multilayers

Author

Gerardi, C., Tagliente, M.A., Del Vecchio, A., Tapfer, L., Coccorese, C., Attanasio, C., Mercaldo, L.v., Maritato, L., Slaughter, J.M., and Falco, C.M.

Subjects
Mass spectrometry -- Usage, Superlattices as materials -- Research, Thin films, Multilayered -- Research, Physics
Abstract

The structural characteristics of superlattices made of 10 periods were investigated using highly depth-resolved secondary ion mass spectrometry and x-ray specular reflectivity.

Published
2000

26. X-ray diffraction study of intentionally disordered (GaIn)As/Ga(PAs) heterostructures

Author

Rettig, R., Marschner, T., Stolz, W., and Tapfer, L.

Subjects
Quantum wells -- Research, X-ray diffractometer -- Usage, Physics
Abstract

The effects of layer thickness variations and deviation from perfect periodicity on high resolution x-ray diffraction (XRD) profiles were studied for (GaIn)As/Ga(PAs) symmetrically strained multiple quantum well heterostructures. Thickness modulation of the compressively restricted (GaIn)As layers resulted into peak splitting mainly on the tensile trained portion of the XRD pattern while modulating the tensile strained Ga(PAs) layer causes splitting on the compressively strained side.

Published
1998

28. Structural ordering and chemical configuration of Ba-based infinite-layer superlattices

Author

Vecchio, A. Del, Mirenghi, L., De Caro, L., Tapfer, L., Aruta, C., Petrocelli, G., and Balestrino, G.

Subjects
Superlattices as materials -- Research, Barium -- Research, Chemical structure -- Research, Physics
Abstract

A study was conducted on BaCuO2/CaCuO2 superlattices grown on (001) SrTiO3 substrates by pulsed laser deposition method. The results indicate that the BaCuO2/CaCuO2 superlattices are grown pseudomorphically on the SrTiO3 substrate. Moreover, the Ca is partially oxidized while Ba is completely oxidized. The findings show that the pulsed laser deposition method permits the fabrication of high quality infinite-layer superlattices of high structural and chemical ordering.

Published
1997

29. Amorphous magnetic films produced by pulsed laser deposition

Author

Nikitin, P.I., Beloglazov, A.A., Toporov, A.Yu., Valeiko, M.V., Konov, V.I., Perrone, A., Luches, A., Mirenghi, L., and Tapfer, L.

Subjects
Metallic films -- Research, Laser industry -- Research, Amorphous substances -- Magnetic properties, Physics
Abstract

ZeCl excimer laser ablation of amorphous magnetic ribbons have been used to create amorphous magnetic Fe-Co-Ni-Si-B films on silicon and glass substrates using variable laser fluence, pulse numbers and target to substrate distance. Ellipsometry, x-ray specular reflectivity, x-ray photoelectron spectroscopy, profilometry and x-ray diffraction show that laser ablation results in good composition and structure transfer from ribbon targets to deposited films.

Published
1997

34. Structural and optical studies of In(sub x)Ga(sub 1 - x)As/GaAs multiple quantum wells

Author

Di Dio, M., Lomascolo, M., Passaseo, A., Gerardi, C., Giannini, C., Quirini, A., Tapfer, L., Giugno, P.V., De Vittorio, M., Greco, D., Convertino, A.L., Vasanelli, L., Rinaldi, R., and Cingolani, R.

Subjects
Gallium arsenide semiconductors -- Optical properties, Chemical vapor deposition -- Usage, Quantum wells -- Research, Spectrum analysis -- Usage, Physics
Published
1996

40. Structural analysis of ZnS/GaAs heterostructures grown by hydrogen transport vapor-phase epitaxy

Author

Giannini, C., Peluso, T., Gerardi, C., Tapfer, L., Lovergine, N., and Vasanelli, L.

Subjects
Semiconductors -- Research, Crystals -- Structure, Physics
Abstract

The structural characterization of the ZnS epilayers reveals that the ZnS lattice exhibits an orthorhombic distortion. The ZnS epilayers are grown by hydrogen transport vapor-phase epitaxy on GaAs structures. The residual strain temperature and residual strain tensor is dependent on the epilayer when the temperature is between 25 and 650 degrees Celsius. The crystallographic symmetry exhibited by ZnS is attributed to the asymmetric distribution of the misfit dislocation.

Published
1995

44. Carbon incorporation in GaAs and AlxGa1-xAs layers grown by molecular-beam epitaxy

Author

Giannini, C., Gerardi, C., Tapfer, L., Fischer, A., and Ploog, K.H.

Subjects
Thin films -- Research, Epitaxy -- Research, Carbon -- Research, Physics
Abstract

The characteristics of GaAs and AlxGa1-xAs thin films grown by molecular beam epitaxy were investigated using high-resolution double-crystal x-ray diffraction, Hall effect measurements and secondary-ion-mass spectroscopy. The results showed that carbon was preferentially incorporated as an acceptor on As lattice sites in both types of thin film samples. In addition, the total amount of carbon incorporated on the As sites was quite large.

Published
1993

45. Radiative transitions in quaternary In0.52Ga0.18Al0.30As layers grown by molecular beam epitaxy

Author

Rinaldi, R., Cingolani, R., Ferrara, M., Tapfer, L., Kunzel, H., and Hase, A.

Subjects
Semiconductors -- Research, Radiative transfer -- Research, Physics
Abstract

The structural and optical characteristics of quaternary In0.52Ga0.18Al0.30As layers grown by molecular beam epitaxy were investigated using high resolution x-ray diffraction, absorption, photoluminescence and photoreflectance spectroscopy. The results showed that several transitions related to impurities and a free exciton feature were present, indicating that the exciton binding energy was smaller than predicted.

Published
1993

46. Optical and structural properties of ternary alloy AlxGa1-xAs/AlAs multiple-quantum-well structures

Author

Dabbicco, M., Cingolani, R., Ferrara, M., Tapfer, L., Fischer, L., and Ploog, K.

Subjects
Quantum wells -- Research, Physics
Abstract

The optical and structural characteristics of ternary alloy AlxGa1-xAs/AlAs multiple-quantum-well structures were investigated. The results showed that the direct energy gap was proportional to the AlAs mole fraction and the band offset ratio was determined by the composition of the alloy. In addition, exciton absorption bleaching occurred in the material.

Published
1992

47. Structural properties and transport characteristics of psuedomorphic Ga(x)In(1-x)As/Al(y)In(1-y)As modulation-doped heterostructures grown by molecular beam epitaxy

Author

Tournie, E., Tapfer, L., Bever, T., and Ploog, K.

Subjects
Epitaxy -- Research, High-electron-mobility transistors -- Research, Physics
Abstract

The structural and transport characteristicsof non-lattice matched GaInAs/AlInAs modulation-doped heterostructures grown onInP by molecular-beam epitaxy were analyzed. The results show that the utilization of thin spacer layers produces extremely high conductivities. In addition, the structures were observed to be psuedomorphic and in excess of calculated critical thickness.

Published
1992

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