What is the core idea behind the scanning tunneling microscope?
The fundamental principle relies on quantum tunneling. Imagine trying to roll a ball over a hill; it needs enough energy to get to the top. But in the quantum world, there's a chance the ball can 'tunnel' right through the hill, even without enough energy. The STM uses this. We bring a very sharp conducting tip extremely close to a conducting surface – so close that electrons can tunnel across the tiny gap. This tunneling current is exquisitely sensitive to the distance. By scanning the tip across the surface and keeping the current constant by adjusting the tip's height, we can map out the contours of the surface, revealing individual atoms.
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