Atomic Force Microscope Technology

The core technology utilized in AFMWorkshop atomic force microscopes was developed by pioneering scientists at IBM, government laboratories, and universities throughout the world. For example:

Light Lever Force Sensor

The light lever force sensor had its origins in the work of precision engineers working on surface profilers. In 1932, Smaltz presented a light lever stylus profile that used film to record the movement of a sharp probe as it scanned across a surface. (1) This technique was first applied to AFM by Amer, an IBM scientist. The light lever force sensor is now the standard in AFM designs. (2)

Vibrating Mode AFM

As with the light lever force sensor, vibrating probe instruments were developed first for surface profilers. It was discovered that by vibrating the probe above a surface as it was scanned, lateral forces on the probe were reduced. (3) Although Binnig and Quate discussed vibrating modes in their pioneering paper, (4) it was a team of IBM scientists led by Kumar Wickramsinghe that first applied vibrating techniques to the AFM. (5) Wickramsinghe's group found that they were able to make the technique sensitive enough that they did not have to tap the surface. The AFMWorkshop does not recommend tapping the surface in vibrating mode AFM. This is possible using the technology developed by IBM scientists.

Feedback Circuits

The first scanning tunneling microscope developed at IBM in Switzerland utilized analog feedback to control the relationship between the probe and surface while measuring an image.(6) This is very similar to the pioneering work of Young at the NBS. (7) Soon after that pioneers such as A. Lewis built scanning probe microscopes with digital feedback(8). However, because of the limitations of ADC and DAC converters, AFM Workshop uses high-fidelity analog feedback circuits to control the Z position of the probe/sample in its microscopes.

Re-Trace Technology

In a scanning probe microscope it is often advantageous to store height information while scanning a sample. This stored information can then be used for a following scan to hold the probe at a fixed distance above a sample's surface. This technique was pioneered by University of Texas professor Alan Bard. (9)

For a more complete introduction to Atomic Force Microscopy, we recommend Atomic Force Microscopy, by Peter Eaton and Paul West, published by Oxford University Press.

References

  1. Gustav Schmaltz, Über Glätte und Ebenheit als physikalisches und physiologisches Problem. In: Zeitschrift des Vereins Deutscher Ingenieure, 12. Oktober, 1929, S. 1461-1467
  2. G. Meyer, N.M. Amer, Novel Optical Approach to Atomic Force Microscopy, App. Phys. Lett., 53(12), 1988, p 1045-47
  3. U.S. Patent 2,728,222 and UK Patent 2,009,409
  4. G. Binnig and C.F. Quate, Ch. Gerber, Atomic Force Microscope, Phys. Rev. Letters, Vol. 56, No 9, p 930
  5. Y. Martin, C.C. Williams, H. K. Wickramasinghe, Atomic Force Microscope Mapping and Profiling on a sub 100-A scale. J. Appl. Phy. Vol 61, No 9, 1987, p 4723
  6. G. Bennig, H. Rohrer, Ch. Gerber, E Weibel, Surface Studies by Scanning Tunneling Microscopy, Phys. Rev. Lett., Vol. 49, No. 1, 1982 p 57
  7. R. Young, J. Ward, F. Scire, The Topographiner: an Instrument for Measuring Tunneling Microtopography, Rev. Sci. Inst., Vol 43, No 7, 1972 p 999
  8. A. Hartoonian, E. Betzig, M. Isaacson, A. Lewis, Super-resolution fluorescence near-field scanning optical microscopy, Appl. Phys. Lett., 49,(11) 15 Sept.1986, p 674
  9. C. Lin, F.F. Fan, A.J. Bard, High Resolution Photoelectrochemical Etching of n-GaAs with the Scanning Electrochemical and Tunneling Microscope, J. Electro. Soc. Vol 134, No 4, 1987, p 1038