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:
“A writer who writes, “I am alone” ... can be considered rather comical. It is comical for a man to recognize his solitude by addressing a reader and by using methods that prevent the individual from being alone. The word alone is just as general as the word bread. To pronounce it is to summon to oneself the presence of everything the word excludes.”
—Maurice Blanchot (b. 1907)
“See how peaceful it is here. The sea is everything. An immense reservoir of nature where I roam at will.... Think of it. On the surface there is hunger and fear. Men still exercise unjust laws. They fight, tear one another to pieces. A mere few feet beneath the waves their reign ceases, their evil drowns. Here on the ocean floor is the only independence. Here I am free.”
—Earl Felton, and Richard Fleischer. Captain Nemo (James Mason)
“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)