Recent studies of thin films and surfaces by high-Resolution electron microscopy
- PDF / 3,658,253 Bytes
- 8 Pages / 630 x 792 pts Page_size
- 31 Downloads / 218 Views
I.
INTRODUCTION
R E C E N T improvements in instrumentation have pushed the structural resolution limit of the electron microscope to beyond the 0.2-nm barrier, thereby making it feasible to resolve directly details of individual atomic arrangements at defects in oxides, semiconductors, and metals and at discontinuities, such as surfaces and interfaces. Applications of the high-resolution electron microscope (HREM) are expanding rapidly as more and more laboratories worldwide purchase the highresolution instruments available commercially. In this review, we first provide a brief overview of the requirements for instrumentation and microscope operation which have contributed to this realization of atomic resolution. We then describe in some detail recent highresolution studies of thin films and surfaces in our laboratory that should serve to emphasize the usefulness and impact of the HREM on the science of materials. Further details of the technique and an extensive list of original references can be found elsewhere, tq II. H I G H - R E S O L U T I O N ELECTRON MICROSCOPY Although the wavelength of a highly energetic electron beam is much less than 0.10 nm (e.g., Al00kV = 0.0037 nm), resolution limits are in the 0.1- to 0.3-nm range, and there are numerous practical factors which can still prevent the image resolution from reaching such
DAVID J. SMITH, Professor, M.R. McCARTNEY, Postdoctoral Research A~sociate, and S.-C.Y. TSEN, Postdoctoral Research Associate, are with the Center for Solid State Science, Arizona State University, Tempe, AZ 85287-1704. ROB W. GLAISHER, Postdoctoral Research Associate, is with the Electron Microscope Unit, University of Sydney, Sydney, New South Wales 2006, Australia. Z.G. LI, Research Scientist, is with E.I. Du Pont de Nemours, Inc., Wilmington, DE. PING LU, Postdoctoral Research Associate, is with the Department of Mechanics and Materials Science, Rutgers-The State University, Piscataway, NJ 08855. A.K. DATYE, Associate Professor, is with the Department of Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131. This invited critical overview paper is based on a presentation made in the symposium "Structure and Properties of Fine and Ultrafine Particles, Surfaces and Interfaces" presented as part of the 1989 Fall Meeting of TMS, October 1-5, 1989, in Indianapolis, IN, under the auspices of the Structures Committee of ASM/MSD. METALLURGICAL TRANSACTIONS A
theoretical values. These are discussed further in a recent monograph. [21 The major physical limitation is the anavoid~ble spherical aberration of the magnetic objective lens, w h i c h determines the m a x i m u m angular a0erture of the electron beam that can be used for image formation. Under appropriate imaging conditions, the effective resot~ion of the conventional transmission electron microscope for intuitive image interpretation is given by ~ 0 . 6 6 C ~ / 4 A 3/4
[ 1]
where Cs is the spherical abberation coefficient of the objective lens. Typical values range from 0.29 nm at 100 kV (Cs = 0
Data Loading...
