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"Our work, it seems to me, can bring us a special bonus of pleasure and satisfaction, through its very close contact with colleagues of different disciplines and our ability to peep into the inexhaustible world of the smallest forms of existence..." Ernst Ruska, Opening Address, IVth Intern. Congr. Electron Microscopy, Berlin, 1958 (English Translation by T. Mulvey, Adv. Imaging & Electron Physics, Academic Press, Vol. 96, xix, 1996) 

"Our century has seen the creation of new means of doing research. In particular, the electron microscope and chemical and biochemical methods of analysis have revolutionized our knowledge of the foundations of life..." Andrei Sakharov, Lecture in Lyons (France): Science and Freedom. September 27, 1989 (Physics Today, 52/7, 22, 1999).

"In case there are people out there who still think TEM is just taking pretty pictures to fill up one's bibliography, please stop, pause...and digest the extraordinary intellectual demands required of the microscopist in order to do the job properly: crystallography, diffraction, image contrast, inelastic scattering events, and spectroscopy." Gareth Thomas, Berkeley: Foreword to the textbook "Transmission Electron Microscopy I-IV" by D.B. Williams & C.B. Carter, Plenum, New York, 1996.

Electron Microscopy & Microanalysis Laboratory (EM&Mlab)

Historisches Lichtmikroskop.2
Light microscope by Antoni van Leeuwenhoek from Delft (1632-1723), maximum magnification: 270 (With kind permission from the Museum for the History of Sciences, Ghent University, Belgium)

Electron microscopy and related spectroscopic methods for quantitative structure analysis, such as energy filtering microscopy/electron energy loss spectroscopy (EFTEM/EELS) or energy-dispersive x-ray analysis (EDX), are indispensable tools in condensed matter research. Recently, these methods have become particularly important within the context of increasing research activities in the field of inorganic, organic and hybrid nanostructures. The investigation of organic materials has made enormous progress thanks to cryo-protection techniques, low-dose and low-voltage applications, and tomographic imaging. This equally holds for surface scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM).

Appropriate and conscientious sample preparation is most crucial for being successful in electron microscopy. While in SEM careful mounting of the sample is required along with eventual metal-coating, well-established preparation techniques for TEM of inorganic specimens include ion-beam milling, nowadays completed with the focused ion beam technique. Soft matter materials usually need special fixation and staining procedures, and thin-sectioning by (cryo)-microtomy using a diamond knife.

High-resolution transmission electron microscopy (HRTEM) of thin specimens (thickness <5nm) allows to investigate spatial atomic configurations and structure defects in a material by phase contrast or diffraction contrast imaging, and by electron diffraction. The conventional 300 keV JEM-3010 microscope with LaB6 electron source, for example, reaches a point resolution of 0.17nm, and a lattice resolution of 0.14nm.

300 keV TEM
300 keV high-resolution transmission electron microscope, maximum magnification: 1,500,000 (JEOL Ltd., Japan)

The development of aberration-corrected S/TEMs during the last decade has made a huge step towards sub-Ångström resolution (see STRL). The resolving power of the newest generation of instruments is now capable of distinguishing atomic distances and compositions across half the diameter of a hydrogen atom, and advanced aplanatic systems will provide high resolution over a large field of view (M. Haider, MC2011, Kiel). Incoherent high-angle annular dark-field (HAADF) or "Z-contrast" imaging mode in STEM is thereby an extremely powerful tool.

At the interdisciplinary EM&Mlab we are providing scanning and transmission electron microscope and x-ray analytical facilities along with necessary sample preparation lines to students and scientists of the Philipps University, and to external users from other institutions and from industry. According to demand, this includes technical support, practical advice and service and, if appropriate, training of students/researchers to learn handling the equipment independently. Besides, we are carrying out own basic research and are involved in international collaborative projects.

Zuletzt aktualisiert: 01.03.2012 · Andreas Schaper

Wissenschaftliches Zentrum Materialwissenschaften

EM&Mlab, Hans-Meerwein-Straße, 35032 Marburg
Tel. +49 6421 28-23456, Fax +49 6421 28-23383, E-Mail: schaper@staff.uni-marburg.de

URL dieser Seite: http://www.uni-marburg.de/wzmw/forschung/ag_schaper

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