IFF
Scientific Report 1998/1999

The Institut für Mikrostrukturforschung (Institute for Microstructure Research) is working in a number of scientific fields. These were selected with an emphasis on modern-materials aspects, on the importance of an atomistic and microstructural understanding for their performance and, if possible, on the possibility of an evolution of research work into technical devices. The goal is an interdisciplinary research group working on a spectrum of scientific problems sufficiently wide to allow a flexible and rapid reaction to new scientific developments. In some of these fields the competence should span the whole range from materials preparation via basic physics investigations to technical devices. In others access to interesting materials and device problems is provided by qualified collaborations inside and outside the Jülich research center. Besides this general-physics and technology part of the institute there is a second part of special competence, the structural research by means of the most modern equipment in transmission electron microscopy and scanning tunneling microscopy. This work is carried out within the Center for High-Resolution Electron Microscopy which is operated by the institute and which at the same time serves a wider community of users.

The research fields can be characterized as follows:

(1) Ceramic Superconductors: Here the emphasis is (a) on thin-film and heterostructure production, Josephson effects, tunneling devices and their application in magnetometer systems and spectroscopic techniques. In addition (b) our investigations on high-frequency properties of ceramic superconductors has evolved into the technology of dielectric resonators and filters for communication applications.

(2) Semiconductors: Here the emphasis is on III-V compounds. In collaborations with various research groups we are studying, mainly by transmission electron microscopy, the growth of thin films and heterostructures. In recent years the problems related to the production and application of low-temperature GaAs have been of special interest. Another topic is the application of scanning tunneling microscopy to the study of the electronic states in compound semiconductors. Here a technique is employed which was pioneered in our group and which permits, via the detection of the far-reaching Debye screening effects of charged doping or impurity atoms at the surface, an investigation of defect related phenomena in the bulk of the samples.

(3) Metallic Alloys: Here the emphasis is on quasicrystalline alloys and their closely related normalcrystalline approximants. Our crystal-growth group is growing large single-quasicrystals for our own research but also for users world-wide, in particular for the participants in the DFG priority program on quasicrystals. Our own work on quasicrystals and approximants concentrates on plasticity and surface physics.

(4) Electroceramics: In the field of electrocermic materials we take advantage of our long-standing experience with respect to perovscitic materials both in preparation and in microstructure research by means of transmission electron microscopy. In collaboration with the Institute of Electroceramic Materials (Prof. Waser) we dedicate a large research capacity to the investigation of the structural aspects of the production and properties of thin electroceramic films.

(5) High-Resolution Electron Microscopy: Although in the beginning primarily considered as a tool for high-quality materials investigations in atomic dimensions the theoretical, methodical and technical aspects of atomic-resolution transmission electron microscopy have become in recent years one of the central fields of interest of our group. We have developed special competence in the theory of high-resolution electron microscopy. Advanced application packages for the exit wave-function reconstruction are installed and serviced by us world-wide in electron-microscopic user facilities. Since 1991 and 1997 we have in collaboration with EMBL Heidelberg and Technical University of Darmstadt developed the word's first aberration-corrected transmission electron microscope with record resolution, 1.3 Å at 200 kV. These developments are continued (see below).

With respect to the equipment the state can be described as follows:

The institute has at its disposal sputtering deposition machines, some of them with three-target facilities which were developed and built in the institute for the high-precision deposition of ceramic superconductor thin film and heterostructures, in particular dc-SQUID devices. In addition for this device production local clean room facilities, structuring and packaging facilities are available.

For high-frequency superconductivity measurement equipment for up to 20 GHz and spectroscopic equipment in the frequency range of 100 GHz up to 2 THz is available. The design of dielectric resonators and filters is optimized by means of finite-element calculations.

The institute operates together with the Institut für Streumethoden (Prof. Brückel) the laboratory for crystal-growth which was part of the former Institut für Materialentwicklung (Prof. Wenzl). This permits to maintain part of the outstanding expertise of this institute in the field of crystal growth. Beyond doubt the whole Department will take advantage of such a materials preparation facility.

The Institute für Mikrostrukturforschung operates the Jülich Center for High-Resolution Electron Microscopy. This contains two 400 kV JEOL machines of the type 4000 EX/FX, a JEOL 2000 EX, a PHILIPS CM 20 FEG and a JEOL 840 A scanning microscope. The most recent instrument is the spherical-aberration corrected PHILIPS CM 200 FEG, the world's first aberration-corrected transmission electron microscope developed by the institute in a collaboration financed by the Volkswagen-Stiftung. This instrument is now in a good working condition and it is operated as a user facility with national and international guests.

The priority in scanning tunneling microscopy is on high-temperature investigations a field only rarely served by other competing groups. Our scanning-tunneling microscopy group has at its disposal two microscopes with in-situ cleavage facilities and ex-situ heating up to 750 °C. These machines were designed and built inside the institute. An in-situ heating STM has been ordered from Omicron to be delivered in May 1999.

Although the institute has an extended in-house program for materials plasticity since about five years it never operated its own deformation machine. We received funds from various sources which permitted us to install (together with the group of Prof. Ullmaier) end of 1998 our own ZWICK mechanical testing system. The excellent collaboration in the plasticity field with the MPI für Mikrostrukturphysik, Halle, (Prof. Messerschmidt) will be continued.

The cooperation with BOSCH in the framework of the BMBF-Consortium "High-Temperature Superconductor Systems for Satellite Communication" is very productive. In particular the multipole filters designed in the PhD-thesis work of St. Schornstein have received considerable attention. We consider it as an outstanding success that our institute, as partner of BOSCH, has won the competition for one of the five priority programs (Leitprojekte) of the German Federal Minister of Science and Technology (BMBF). The Title: "High-Temperature Superconductivity for the Communication Technology of the Future". The institute also succeeded in a competition for funding of a project with the same title by the "Strategiefonds of the Hermholtz-Gemeinschaft Deutscher Forschungszentren (HGF)".

Our dc-SQUIDs on the basis of ramp-type junction geometry continue their success both in performance and in their acceptance in application and on the market. As a supplier of TRISTAN Company (USA, formerly Conductus) we deliver a larger number of SQUIDs and magnetometers per month. New developments concern flux transformers and gradiometers where the market demands (and commercial orders) directly meet our scientific interests. Our dc-SQUIDs are also employed in a number of projects carried out together with the Institut for Thin-Film and Ion-Technology (Prof. Braginski) and the ZEL (Prof. Halling).

Our developments of Hilberttransform spectroscopy on the basis of Josephson-Junctions are bearing ample fruit. Hilberttransform spectroscopy provides an excellent and novel tool for spectroscopy in the frequency range of 10¹⁰ to 10¹³ Hertz, more than three orders of magnitude faster than Fourierspectroscopy. Here we have an excellent collaboration with the Institute for Radioelectronics in Moscow. We succeeded in acquiring a BMBF-project for the development of a fast gas-spectromer and a project with DESY, Hamburg. The latter is a consequence of our successful test of Hilberttransform spectroscopy for the determination of the shape of electron bunches in the beam in the TESLA accelerator test facility in Hamburg. This technology has the chance to become the basic technology for beam diagnostics in the final installation. Other projects concerning this novel technique have been submitted to international funding agencies.

The successful project of the spherical-aberration corrected transmission electron microscope described above has triggered a priority program of the DFG. In the framework of this new program granted in 1998 our institute will develop in collaboration with CEOS Company, Heidelberg, and Zeiss-LEO, Oberkochen, the world's first Subangström-Instrument. Besides ultra-high resolution the 200 kV machine will contain a monochromator and an in-column energy filter of the Krahl-type. Another two instruments further optimized for high-resolution analytic functions will be installed at the University of Münster and at the MPI für Metallforschung in Stuttgart. Delivery is planned for 2003. This will maintain the institutes position as a pioneer in advanced instrument development.

The institute is partner of PHILIPS ELECTRON OPTICS with respect to the theory and application of exit-wave function reconstruction techniques in high-resolution transmission electron microscopy. In this field our institute is respected as a key institute. Advanced application packages for the exit wave-function reconstruction are installed and serviced by us world-wide, under PHILIPS contract in electron-microscopic user facilities. The key role in this field is further illustrated by a large number of visits by international experts.

The quasicrystal group has currently three DFG funded projects which, after running now for two years, will enter the second phase in May 1999. In these as well as in other parts of our research program the shortage in manpower has not been without influence. Delays resulting from problems to find good PhD students and post-docs were and are unavoidable. It is the clear institute policy to maintain high-quality standards and, in the extreme, to return funds rather than yield to the personnel-related difficulties. Great efforts went into a new PhD program with the Russian Academy of Sciences and other GUS state universities and universities in China. In the framework of this special program designed by the institute and the partners abroad the PhD students are working two years in Jülich on a grant supervised by the Jülich Doktorandenausschuß, but they will pass their examina in their home university. Two PhD students are working now in the institute on this basis. Others financed by other sources (e.g. by the Humboldt Foundation) come from China.

(Total 14 - 7 Scientists)

Post-docs (Total 6)

Doctor students (Total IO)

Diploma students (Total 4)

Guests (Total 3)