Metallurgical analysis and RF losses in superconducting niobium thin film cavities

Copper cavities with a thin niobium film as used in the large electron positron collider LEP would be also attractive for future linear colliders, provided the decrease of the Q-value with the accelerating gradient can be reduced. We aim at extracting the important parameters that govern this decrease. The dependence on the RF frequency is studied by exciting 500 MHz and 1500 MHz cavities in different modes. In addition we combined RF measurements for two 1500 MHz cavities of different RF performance with microscopic tests (AFM, TEM) on samples cut out of the same cavities. Their micro-structural characterisation in plan-view allows to extract the grain size and the defect densities

The absence of antiferromagnetic coupling and GMR effect in evaporated permalloy/Cu multilayers, in situ transport properties

Lucinski T, Reiss G, Mattern N, van Loyen L. The absence of antiferromagnetic coupling and GMR effect in evaporated permalloy/Cu multilayers, in situ transport properties. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. 1998;189(1):39-46.Thermally evaporated (permalloy Ni80Fe20)/Cu multilayers were deposited on to quartz glass substrate, oxidised Si and etched Si wafers at room temperature and at 100 K. The samples were examined during an evaporation process by means of in situ conductance measurements whereas magnetisation, X-ray diffraction, atomic force microscopy and the cross-section electron transmission microscopy were performed ex situ to characterise our samples. Only a very small GMR effect was observed for samples deposited at RT and at 100 K. An absence of the antiferromagnetic coupling seems to result from the large interface roughness. Multilayers deposited at 100 K showed the existence of a highly topological disordered alloy-like structure formed during the deposition process. (C) 1998 Elsevier Science B.V. All rights reserved

High reflection optics and high precision metrology for extreme ultraviolet (EUV) light

The ever-decreasing pattern size of structures in integrated circuits requires lithography processes using light of ever-shorter wavelengths. Currently, laser light with wavelengths of 248 nm and 193 nm is used for the illumination in production lines of semiconductor factories. However, since several years many research groups are already dealing with the most promising next generation lithography, the extreme ultraviolet lithography (EUVL) that will use light with a wavelength of 13,5 nm. This paper summarizes recent research and development results of IWS Dresden in the field of preparation of EUV reflection optics and EUV metrology

Characterization of Ni80Fe20/Cu multilayers by X-ray reflection using anomalous scattering

Meyer DC, Richter K, Wehner B, Reiss G, van Loyen L, Paufler P. Characterization of Ni80Fe20/Cu multilayers by X-ray reflection using anomalous scattering. In: EUROPEAN POWDER DIFFRACTION, PTS 1 AND 2. Vol 321-3. TRANS TECH PUBLICATIONS LTD; 2000: 451-456.Ni80Fe20/Cu muitilayers (Ni80Fe20=Py) belong to the sample systems, which show a Giant Magneto Resistance (GMR) interesting for magneto-electronic applications. The magnetic exchange coupling and thus the GMR depend sensitively on the layer structure and on the conditions of deposition. Regarding the structure characteristic correlation still clearing-up need exists. The composition of the layers from elements, which are neighbored in the periodic system of the elements, makes it necessary to use anomalous scattering conditions for the characterization by X-ray reflectometry. Therefore experiments were done with synchrotron radiation. Layer thickness, density of the layers and roughness of interfaces have been determined by fitting model parameters to the reflection curves. From fluorescence EXAFS measurements (Extended X-ray Absorption Fine Structure) near the Fe-K, Ni-K and Cu-K absorption edges the conclusion has been drawn that radial distributions of atoms in the thin layers correspond to those of compact polycrystalline material. Differences of the GMR values of the investigated samples can be attributed exclusively to the layer thickness and thickness relations, while influences of the roughness of the interfaces and structural differences play a subordinate role

Presence and absence of antiferromagnetic coupling and giant magnetoresistance in sputtered and evaporated permalloy/copper multilayers

Reiss G, van Loyen L, Lucinski T, et al. Presence and absence of antiferromagnetic coupling and giant magnetoresistance in sputtered and evaporated permalloy/copper multilayers. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS. 1998;184(3):281-288.In multilayered thin films consisting of permalloy (Ni80Fe20) and copper, a strong antiferromagnetic coupling and a related giant magnetoresistance can be found which oscillates with the thickness of the copper spacer layers. This, however, is usually detected only in sputtered films, whereas evaporated multilayers often show no or only a very weak coupling and giant magnetoresistance. Here, we report on a comparative study of sputtered and evaporated multilayers. In the first maximum of the antiferromagnetic coupling, i.e. at a copper thickness of 0.9 nm, our sputtered films exhibit a saturation field of up to 1000 Oe and values of the giant magnetoresistance of up to 22% at room temperature at a permalloy thickness of about 2 nm. In contrast to this, the corresponding evaporated multilayers do not show any sign of antiferromagnetic coupling. A subsequent analysis of the films by cross-sectional transmission electron microscopy imaging indicates, in small regions, a good and a poor multilayered structure for sputtered and evaporated films, respectively. X-ray reflectivity measurements and atomic force imaging of the surfaces pointed to an increased interface roughness in the evaporated films. Thus we conclude that the absence of the antiferromagnetic coupling in the evaporated films should be related to an increased roughness of the layer interface and not to interdiffusion. (C) 1998 Elsevier Science B.V. All rights reserved

Konzeption und Erprobung eines Labor-Reflektometersystems fuer Roentgenoptiken Schlussbericht

Available from TIB Hannover: F04B1373 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman