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Atomic-Force Microscopy (AFM)

Introduction

Atomic-force microscopy is similar to scanning-tunneling microscopy (STM) in that it can image surfaces at atomic-scale resolution. The difference between AFM and STM is that AFM does not require that the sample be an electrically conducting material. Like STM it uses an atomically-sharp tip that is brought very close to the surface. The tip will feel a chemical attraction or repulsion and will move up or down on its supporting cantilever. The key to the sensitivity of AFM is in monitoring the movement of the tip. A common means of monitoring the tip movement is to use a laser beam that is reflected or diffracted by the tip or cantilever. Up or down movement of the tip is then detected by changes in the laser beam position. As in STM, rastering the tip across the surface produces a topographic map of the surface with atomic resolution.


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