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Unformatted text preview: 1 Atomic Force Microscopy 1.1 Introduction Atomic force microscopy (AFM) is also known as scanning force microscopy (SFM). AFM is a basic technique and inevitable for all nanoscopic research. For example all chapters of this book rely on AFM measurements. However the scientific community became interested in the many uses of AFM for (very) rough surfaces at large scan ranges only in 1990 [1–4], and it took two years before these first results were accepted and published [5–7]. Actually, it was not possible in 1989 to convince funding agencies to support the idea of using the three-dimension capabilities of AFM and the author had to purchase all of his nanoscopic instruments privately. Measurements had been made on large biological objects such as whole cells, bacteria, etc. [8, 9]. However, the authors of these studies were only interested in the smallest features ( < 50 nm height) on the surfaces that could be laterally resolved, notwithstanding the two-dimensional projection of the whole object without a z-scale, and the migration of living cells on glass slides in buffer solution. Early high three-dimensional AFM topologies with assessment of the z-scale were made for a dental implant , wear marks on single-crystal silicon , and silver bromide cubic crystals . Like all other scanning probe microscopies (SPM), AFM works by scanning with a tip (or more general a probe) very close to the sample surface. It operates by measuring attractive or repulsive forces between the tip and the sample in constant height or constant force mode. Most spectacular are atomic resolution and manipulation, but most practical applications deal with the (sub)micrometer x/y- and nano z-range. The first atomic force microscope (AFM) was made in 1986. It was of the dynamic type with vertical tip vibration . However, the first commercial instruments (since 1989) were static-force or contact AFMs. Shear-force AFM microscopes with horizontal tip vibration for distance control were developed in 1992 [14, 15]. The dynamic-mode AFM found a new application with the 2 1 Atomic Force Microscopy commercialization of noncontact and tapping-mode AFM [16, 17]. Other sur- face properties such as friction forces, sample elasticity, adhesion, or chemical differences by lateral and torsional force sensing, force modulation, frequency modulation, and phase imaging are available. Magnetic nanostructures are scanned by magnetic force microscopy using cantilever tips that are coated with a ferromagnetic film of a few nm thickness, with most applications of MFM being in the storage media industry. Virtually all solid surfaces from all branches of science, industry, medicine, daily life are accessible to nanoscopic investigation with unprecedented information. The resolution here is much higher than with a microscope and the three-dimensional information is an- other most important distinguishing feature of AFM. It supplements electron microscopy and increases the possibilities, as it does not require surface treat-...
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This note was uploaded on 08/21/2008 for the course EMA 6510 taught by Professor Dempere during the Fall '08 term at University of Florida.
- Fall '08
- The Land