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Atomic Force Microscopy - What is it?

Atomic Force Microscopy - AFM

AFM stands for Atomic Force Microscopy or Atomic Force Microscope and is often called the "Eye of Nanotechnology". AFM, also referred to as SPM or Scanning Probe Microscopy, is a high-resolution imaging technique that can resolve features as small as an atomic lattice in the real space. It allows researchers to observe and manipulate molecular and atomic level features.

How Atomic Force Microscopy works is illustrated in the figure to the right. AFM works by bringing a cantilever tip in contact with the surface to be imaged. An ionic repulsive force from the surface applied to the tip bends the cantilever upwards. The amount of bending, measured by a laser spot reflected on to a split photo detector, can be used to calculate the force. By keeping the force constant while scanning the tip across the surface, the vertical movement of the tip follows the surface profile and is recorded as the surface topography by the AFM.

The predecessor of AFM is STM, Scanning Tunneling Microscopy or the Scanning Tunneling Microscope, was invented in 1981 by G. Binnig and H. Rohrer who shared the 1986 Nobel Prize in Physics for their invention. An excellent technique, STM is limited to imaging conducting surfaces.

Atomic Force Microscopy has much broader potential and application because it can be used for imaging any conducting or non-conducting surface. The number of applications for AFM has exploded since it was invented in 1986 and now encompass many fields of nanoscience and nanotechnology. It provides the ability to view and understand events as they occur at the molecular level which will increase our understanding of how systems work and lead to new discoveries in many fields. These include life science, materials science, electrochemistry, polymer science, biophysics, nanotechnology, and biotechnology.

As shown in the table below, AFM has a number of advantages over other techniques that make it a favorite among leading researchers. It provides easily achievable high-resolution and three-dimensional information in real space with little sample preparation for low-cost. In-situ observations, imaging in fluids, temperature and environmental controls are all available.

Comparison of Atomic Force Microscopy and other Techniques
  AFM TEM SEM Optical
Max resolution Atomic Atomic 1's nm 100's nm
Typical cost
(x $1,000)
100-200 500 or higher 200-400 10-50
Imaging Environment air, fluid, vacuum, special gas vacuum vacuum air, fluid
In-situ Yes No No Yes
In fluid Yes No No Yes
Sample preparation Easy Difficult Easy Easy

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