May 13 2004
.jpg)
Image Credits: Elizaveta Galitckaia/shutterstock.com
The atomic force microscope (AFM), together with the scanning tunneling microscope (STM), was invented in 1986 by Binnig, Quate, and Gerber. Similar to other scanning probe microscopes, the AFM uses a sharp probe that moves over a sample’s surface in a raster scan.
With the AFM, the probe is a tip on the end of a cantilever which bends in reaction to the force between the sample and the tip. The STM and AFM provide images of atoms on or in surfaces.
Properties of the AFM
The AFM functions by scanning a fine ceramic or semiconductor tip over a surface, quite like the way a phonograph needle scans a record (for those who remember what a record player is!). The tip is placed at the end of a cantilever beam shaped almost like a diving board. As the tip is attracted to or repelled by the surface, the cantilever beam deflects.
The magnitude of the deflection is captured by a laser that reflects at an oblique angle from the tip of the cantilever. A plot of the laser deflection versus tip position on the surface of the sample delivers the resolution of the valleys and hills that make up the surface topography.
The AFM can function in two modes—with the tip touching the sample (contact mode), or the tip tapping across the surface (tapping mode) similar to the cane of a blind person. Other measurements can be made using alterations of the AFM. These include differences in surface microfriction with a lateral force microscope (LFM), variations in elastic moduli on the micro-scale with a force modulation microscope (FMM), and orientation of magnetic domains with a magnetic force microscope (MFM).
Atomic Force Microscopy Involvement in Nanotechnology
With atomic force microscopy, it is possible to directly view single molecules or atoms that have dimensions of a few nanometers. Researchers and engineers have been using AFM to observe and measure the dimensions of molecules on real surfaces. However, the properties of the AFM can be expanded further.
Similar to a pen writing on paper, AFM can be used to write on a surface. This obviously means engineers and researchers can carry out many surface alterations on a nanometer scale. It is already possible to alter surfaces by physically scratching the surface. Researchers can place new and exciting molecules on to a surface as well as use electric fields to alter its shape.
The Future of Atomic Force Microscopy in Nanotechnology
Even today, researchers and engineers continue to use atomic force microscopy for exploiting molecules and atoms on surfaces. However, enhancements are still being hunted. The key challenge being the speed in which atoms can be included on the surfaces. There is also the speed at which the molecules or atoms are being altered.
Another issue is since the tip is in direct contact with the real surface, it will encounter problems in case that surface is sticky, soft, or contains loose particles floating on it. However, on the whole, the AFM can be used on most materials and is largely involved in a whole range of technologies from chemical and biological to electronics. It is anticipated that the AFM will play its role in creating many new and stimulating nanotechnology products in the days ahead.