Can you observe an atom

HAADF micrograph of a copper and silver rich precipitate in an aluminium-based alloy. Why would you even want to see something in that much detail? The most obvious, Ramasse said, is because we're always trying to miniaturize devices, which means we need to miniaturize parts like transistors and semiconductors—"and that means you need to design materials or materials' components that are really smaller.

It gets to a point where modifying a material even by an atom or two could change its properties. Add another atom here or there and you've changed the material and potentially modified what it can do.

Keeping an eye on the exact structure is therefore important. Optical light microscopes have been around for many years. You can get magnifications of over times with a modern light microscope. This is enough to see inside plant and animal cells, but not in much detail. The main limit is the wavelength of light. In effect, many nanoscale objects are so small that light aimed at them misses, and so is not reflected back for us to see.

This means that objects of less than nm are distorted under a light microscope. To magnify things more, a new tool was developed. This came in , with the invention of the electron microscope.

Beams of electrons are focused on a sample. When they hit it, they are scattered, and this scattering is used to recreate an image. An electron microscope can be used to magnify things over , times, enough to see lots of details inside cells.

The wavelength of visible light is about 10 -6 m the same as 10 3 nm , as shown in the drawing. The size of a typical atom is about 10 m, which is 10, times smaller than the wavelength of light. How about radiation like light but with a shorter wavelength? X-ray wavelengths are about the same size as atoms, but reflecting x-rays from matter forms a complex pattern of spots that depends on the arrangement of the atoms.

Analysis of these patterns reveals a lot of important information about crystals, but the x-ray images do not show individual atoms. The best way to image atoms is with a device called a scanning tunneling microscope.

It is based on tunneling, a quantum-mechanical effect roughly analogous to water leaking right through the sides of a glass.

If a small needle comes within about 10 -9 m of a metal surface, an electric current, due to tunneling, starts to flow. The size of this current depends upon the separation of the needle and the atom and decreases as the separation increases.

When the imaging laser was off, or turned on only dimly, the atoms tunneled freely. But as the imaging beam was made brighter and measurements made more frequently, the tunneling reduced dramatically. Atoms in this state are extremely sensitive to outside forces, he noted, so this work could lead to the development of new kinds of sensors.