Identification of Individual Surface Atoms
The AFM can be used to image and manipulate atoms and structures on a variety of surfaces. The atom at the apex of the tip "senses" individual atoms on the underlying surface when it forms incipient chemical bonds with each atom. Because these chemical interactions subtly alter the tip's vibration frequency, they can be detected and mapped. This principle was used to distinguish between atoms of silicon, tin and lead on an alloy surface, by comparing these 'atomic fingerprints' to values obtained from large-scale density functional theory (DFT) simulations.
The trick is to first measure these forces precisely for each type of atom expected in the sample, and then to compare with forces given by DFT simulations. The team found that the tip interacted most strongly with silicon atoms, and interacted 23% and 41% less strongly with tin and lead atoms, respectively. Thus, each different type of atom can be identified in the matrix as the tip is moved across the surface.
Read more about this topic: Atomic Force Microscopy
Famous quotes containing the words individual, surface and/or atoms:
“Bunglers and pedants judge art according to genre; they approve of this and dismiss that genre, but instead of genres, the open-minded connoisseur appreciates only individual works.”
—Franz Grillparzer (1791–1872)
“We’ve forgotten what it’s like not to be able to reach the light switch. We’ve forgotten a lot of the monsters that seemed to live in our room at night. Nevertheless, those memories are still there, somewhere inside us, and can sometimes be brought to the surface by events, sights, sounds, or smells. Children, though, can never have grown-up feelings until they’ve been allowed to do the growing.”
—Fred Rogers (20th century)
“It is the way unseen, the certain route,
Where ever bound, yet thou art ever free;
The path of Him, whose perfect law of love
Bids spheres and atoms in just order move.”
—Jones Very (1831–1880)