In a reel to reel MOCVD system YBCO films and buffer layers were deposited on textured NiW-tapes. The layers of all RTR MOCVD Coated Conductors were grown with excellent in plane and out of plane texture with FWHM of 5-7° and 1.4-4° respectively. The critical current densities of these films were up to 1 MA/cm2 at 77 K. MOCVD-YBCO films on MOD CeO2/LZO buffered NiW (delivered by FZ Karlsruhe) could be coated with critical current densities of up to 2 MA/cm2. The 'End to End' critical current of MOCVD-YBCO on MOD-LZO/NiW (delivered by Nexans Superconductors) was 58 A for a 700 nm thick film onto a 10 mm wide tape.

Reel-to-reel MOCVD process for continuous growth of electrically conducting buffer layers on biaxially textured Ni5W tapes has been developed. The new buffer layer architechture is presented: 200 nm (La,Ba)(2)CuO4 / 40 nm (La,Ba)MnO3 / Ni5W. Constituting layers with high structural quality have been grown on moving tapes (in plane FWHM <= 6 degrees and out of plane FWHM <= 3 degrees).

A new MOCVD technique was developed for the deposition of oxides at a controlled low oxygen partial pressure, which enable to coat textured metal tapes with electrical conductive perovskites. In a RTR MOCVD-system metal tapes were coated with electrical conductive (La,Ba)MnO3, (La,Sr)MnO3, (La,Sr,Pb)MnO3 and (La,Ba)(2)CuO4 buffer layers and YBCO. In the same RTR-system YBCO was deposited on different buffered metal tapes. Computer calculations were used to characterise the behaviour for a weak superconducting part of a CC-tape with a conductive buffer layer system.

Buffer layers and YBCO have been continuously deposited on textured Ni5%W tapes in a reel-to-reel MOCVD system. The buffer layers were perovskites with the composition (AA')(BB')O-3 (A, A' = La, Sr, Ca, Ba and B, B' = Cr, Mn, Fe, Co, Ni). The buffer layers were well textured with in-plane FWHM down to 5.5 degrees and out-of-plane FWHM down to 2.2 degrees.

In an article dedicated to Professor George Wahl on the occasion of his 65th birthday, an overview is given of CVD research at the Institute of Surface Technology and Plasma Development of Material (IOPW), and of his contributions to that research and to CVD developments over the last 35 years.

New deposition techniques are used for MOCVD of YBCO-, buffer- and protective layers in a reel to reel system. This system consists of three tape reactors and evaporators. So it is possible to deposit the superconductor, the buffer layer and a protective layer in situ in one vacuum system. The operativeness of the reactors were tested separately. In the YBCO reactor superconducting films have been deposited with critical current densities over 1 MA/cm/sup 2/ at 77 K on moved textured Nickel tapes at a transport velocity of 4 m/h. Textured Ni substrates were coated in the buffer layer reactor with CeO/sub 2/ and in first experiments a Ag layer was deposited by MOCVD onto the YBCO film.

MOCVD is an economic method for the production of coated conductors. A single source MOCVD-system for continuous deposition on metal tapes was developed. Single crystals, IBAD buffered tapes and textured Ni-tapes were transported through the deposition zone and coated with YBCO. The velocity for the substrate transport was 4 m/h. On single crystals and IBAD buffered substrates the best critical current density of the 300–350 nm thick YBCO films were 2.5 and 4.8 MAcm−2 at 77 K. On CeO2/YSZ/CeO2 buffered textured nickel tapes the jc of the 500 μm thick YBCO film was 0.25 MAcm−2 at 77 K. Textured oxide buffer layers were deposited by MOCVD on single crystals and textured Ni in reducing atmosphere.

A new single source MOCVD-system was developed, which can be used to coat continuously textured Nickel tapes. To test the YBCO deposition single crystals and MAD buffered substrates were continuously transported with 4 m/h through the deposition zone. The critical current density of the superconducting layers at 77 K is higher than 4 MA/cm(2) on single crystalline LaAlO3 and higher than 2 MA/cm(2) on IBAD buffered tapes. Two routes for the buffer layer deposition on Ni are chosen: a) NiO is epitaxially grown onto textured Ni by thermal oxidation, b) In reducing atmosphere textured buffer layers were deposited onto nickel.

A vapour source for MOCVD applications has been developed. This source presents a clear advantage when using solid precursors dissolved in an organic solvent. Vapour sources of solid precursors by direct heating are not reproducible; the use of a solution of one or more components is the best way to control the mass sent to the reactor accurately. Several solutions have been proposed to introduce the solution into the evaporation zone. In this work, we present the characterization of a vapour source that allows to separate the solvent from the precursors before introducing the precursors vapours into the deposition chamber. In this way, vapours from the precursors are only sent to the deposition chamber.

ABSTRACT Spectroscopy,of individual light-harvesting 2 complexes,from,purple,photosynthetic,bacteria,revealed,a deformation,of the circular complex,into C2 symmetry.,The present,work,relates the geometry,of the deformed,aggregate,to its spectroscopic,properties. Different models,of elliptical deformation,are discussed,and,compared,with the experimental findings. It is shown that the model with smaller interpigment distances, where the curvature of the ellipse is small, provides the best agreement,with fluorescence,excitation spectra,of individual complexes.

MOCVD is a promising economic method for the production of YBCO tapes. An enlarged single source MOCVD-system for continuous deposition of YBCO on metal tapes was developed. Computer simulations with FLUENT code were used for the design of the new tape system, which is based on a former small tape system. The calculated temperature distribution, precursor mote fractions and gas flows lead to a better understanding of the important aspects of the design. In this new system single crystals, IBAD buffered tapes and buffered textured Ni-tapes were transported through the deposition zone and coated with YBCO. On Single crystals, IBAD buffered substrates and textured Ni the best critical current densities at 77 K of the 300-500 rim thick YBCO films were 4.8 MA/cm(2) 2.5 MA/cm(2) and 0.25 MA/cm(2) respectively. The velocity for the tape transport was 4 m/h for these substrates. The XRD-measurements of the YBCO-film on single crystalline LaAlO3 showed only c-axis orientation with FWHM(005) = 0.10degrees for the rocking curve and with FWHM(102) = 0.7degrees for the phi scan.

This paper reports a detailed spectroscopic study of the B800 absorption band of individual light-harvesting 2 (LH2) complexes of the photosynthetic purple bacterium Rhodopseudomonas acidophila at 1. 2 K. By applying single-molecule detection techniques to this system, details and properties can be revealed that remain obscured in conventional ensemble experiments. For instance, from fluorescence-excitation spectra of the individual complexes a more direct measure of the diagonal disorder could be obtained. Further spectral diffusion phenomena and homogeneous linewidths of individual bacteriochlorophyll a (BChl a) molecules are observed, revealing valuable information on excited-state dynamics. This work demonstrates that it is possible to obtain detailed spectral information on individual pigment-protein complexes, providing direct insight into their electronic structure and into the mechanisms underlying the highly efficient energy transfer processes in these systems.

In a small scale MOCVD system YBCO films with j(c)(77 K) > 1 MA were deposited onto substrates, which were continuously moved through the deposition chamber. Two routes for the buffer layer deposition onto textured Ni tapes were chosen: a) CeO2, LaMnO3 and LaCrO3 films were deposited in hydrogen atmosphere by MOCVD. On LaAlO3 and R-Al2O3 crystals epitaxial films were obtained b) textured NiO layers were grown by oxidation of textured Ni tapes. Based on the small scale system an enlarged MOCVD reactor was constructed.

It is shown that based on spectrally selective excitation of individual molecules in the focus of a high NA lens together with position sensitive imaging sub-resolution imaging of three-dimensional structures can be realized. The feasibility of the idea is demonstrated with NA equals 0.55 optics on a model system of pentacene molecules in p-terphenal host matrix.

o n and t h e d.c.resistance o f a superconducting g r a n u l a r lead

Weakly magnetic m a t e r i a l s may be s epa ra t ed w i th in Open Gradient Magnetic Sepa ra to r s u s ing d r y o r wet p rocesses . Axial-symmet r i c arrangments a r e of s p e c i a l i n t e r e s t when u t i l i z i n g c e n t r i f u g a l f o r c e s i n a d d i t i o n t o magnetic fo r ce s . Thereby g r a d i e n t f i e l d s a r e needed which genera te mainly r a d i a l l y inwards d i r e c t e d fo r ce s . Such fo r ce s form a kind of magnetic p o t e n t i a l b a r r i e r which cannot be t ransversed by magnetic p a r t i c l e s . The necessary f i e l d d i s t r i b u t i o n s can be a t t a i n e d by means of p roper ly shaped c o i l s which a r e arranged s i m i l a r t o t h e known Helmholtz con f igu ra t i on . The layout of such superconducting c o i l s f o r a p p l i c a t i o n s i n c e n t r i f u g a l s e p a r a t o r s i n d i s cussed. I n order t o ga in high magnetic f o r c e s o r ene rg i e s w i th in Open Gradient Yagnetic Sepa ra to r s , it i s adv i sab l e t o use superconduct ing magnets. Axial-symmetric arrangements a r e of s p e c i a l i n t e r e s t , s i nce c e n t r i f u g a l and magnetic f o r c e s may be used a c t i n g a g a i n s t each o t h e r . General ly t h e magnetic f o r c e s a c t i n g on a weakly magnetic p a r t i c l e may be de r ived from the equi l ib r ium of energy w i th in a given system. One can de f ine a mechanical p o t e n t i a l of t h e magnetic f o r c e s by / I / . where 0 means t he s p e c i f i c p o t e n t i a l of t h e f i e l d u0H which i s independent of t h e p r o p e r t i e s of t h e p a r t i c l e s , i . e . t h e volume V and t h e s u s c e p t i b i l i t y x r e spec t i ve ly : One con f igu ra t i on o f t e n used i s a c y l i n d r i c a l mul t ipo le . Fig.1 shows t h e r a d i a l p r o f i l e of t he s p e c i f i c p o t e n t i a l . I t demonstrates t h a t t h e s p e c i f i c magnet ic f o r c e s Fs (which a r e t h e d e r i v a t i o n of t h e p o t e n t i a l , i . e . t h e s l ope of t h e curve) i nc r ea se very r a p i d l y near t he winding. On t h e o the r hand, they vanish q u i t e qu ick ly a s t h e d i s t a n c e i nc r ea se s So i f one needs a c e r t a i n fo r ce , one i s r e s t r i c t e d t o a r e l a t i v e l y smal l a r e a which is narrowed even f u r t h e r by t h e need f o r thermal ins u l a t i o n . I n a d d i t i o n , p a r t i c l e s may s t i c k t o t h e ou t e r wa l l un l e s s s p e c i a l cond i t i ons a r e met. Th i s i s t h e main disadvantage of a l l Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19841160

A new MOCVD technique was developed for the deposition of oxides at a controlled low oxygen partial pressure, which enable to coat textured metal tapes with electical conductive perovskites. In a RTR MOCVD-system metal tapes were coated with electrical conductive (La,Ba)MnO3, (La,Sr)MnO3, (La,Sr,Pb)MnO3 and (La,Ba)2CuO4 buffer layers and YBCO. In the same RTR-systemYBCO was deposited on different buffered metal tapes. Computer calculations were used to characterize the behaviour for a weak superconducting part of a CC-tape with a conductive buffer layer system.