Scanning Tunneling Microscopes

Invented:

1981

Cost:

$o Much Money

Resolution:

1x10^-11m (depth)

1x10^-10m (lateral)

How do Scanning Tunneling Microscopes work?

Scanning Tunneling Microscopes run a tip very low above the surface (0.4 to 0.7 nanometers), and run a voltage through it. They then measure the current, which is only there because some of the electrons quantum tunnel between the tip and the surface. As the electrons tend to tunnel more frequently over shorter distances, the current is a very accurate measure of the height of the surface, and the currents can be used to produce an image of the surface.

What are the advantages and disadvantages?

Advantages:

• Very very very high resolution - 1 hydrogen atom in width, and 0.1 hydrogen atoms in depth. When would you ever need that sheer amount of detail?
• Doesn't require a vacuum or special temperatures - It can be used in most circumstances: ultra-high vacuum, air, water, most fluids and temperatures ranging between asolute zero and a thousand degrees Kelvin.
• Provides a 3D topographical image (as opposed to a 2D top-down image)

Disadvantages

• Very very very expensive - even for an atomic scale microscope
• Very fragile - needs to have clean surfaces, and used as exactly as possible
• Can't find a third disadvantage...

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