You could be forgiven for not reading the small print just produced by physicists at Stanford University. Their letters equal the record for the smallest ever made, at just 1.5 nanometres tall.
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The new letters are around a third of the size of the atomic letters made in 1990 by Donald Eigler and Erhard Schweizer at IBM.
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The pair used a (STM) to push 35 xenon atoms across a nickel surface and spell out the company鈥檚 name in letters just 5 nm tall.
A year later, researchers at Japanese firm Hitachi set the record for microscopic calligraphy. Their 1.5-nanometre-tall letters were chiselled into a molybdenum disulphide crystal, again using an STM.
Holographic script
Now and 鈥榮 team at Stanford University have equalled Hitachi鈥檚 record using a holographic variation on the IBM technique.
They started with a similar setup to the IBM team, using a scanning tunnelling microscope to position individual carbon monoxide molecules on a copper surface. However, the atoms are arranged in a complicated circular pattern with a void in the middle.
The team then sent a flow of electrons through the copper, some of which ripple across its surface as waves. The ripples scatter off any carbon monoxide molecules they meet and interfere to project holographic patterns into the central clearing, which can take on a particular shape.
鈥淚magine [the copper as] a very shallow pool of water into which we put some rocks [the carbon monoxide molecules],鈥� says Manoharan. 鈥淭he water waves scatter and interfere off the rocks, making well defined standing wave patterns.鈥� If the rocks are positioned just right, the wave patterns will form into letters.
Molecular projector
The researchers wrote a computer program that works out how to arrange the carbon monoxide molecules such that they scatter electrons into waves of a particular shape. The software also demonstrated how varying the energy of the electrons could produce different shapes from the same pattern of molecules.
Reproducing some of these patterns for real using the STM has so far produced an 鈥淪鈥�, a 鈥淯鈥� and an 鈥淪U鈥� pair (see image, above right), as small as 1.5 nm high.
works on holographic information storage at the University of California in Santa Barbara. 鈥淸This] is an excellent piece of science,鈥� he says.
Being able to write information on such tiny scales could lead to new ways to pack large amounts of data into small spaces.
However, the Stanford team stresses that they鈥檙e not exploring that possibility at the moment as, although the information density is high, it drops off when the space occupied by the surrounding carbon monoxide molecules is taken into account.
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