Cantilever deflection, scanning tunneling microscopy

The two techniques that can be called scanning probe microscopy differ in the method they use to detect interactions. In STM the tip is so close to the sample (both being electrically conducting) that it allows a current to flow by tunnel effect and the sample or tip moves to keep this current constant. In AFM the tip is placed on a cantilever whose deflection can be detected by the reflection of a laser beam appropriately focused. This allows the analysis of nonconducting materials, which makes the method more convenient to study membrane materials [38, 39]. 

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