Washington (IANS): Stanford researchers have reclaimed bragging rights for creating the world's tiniest writing, in sub-atomic letters more than a billion times smaller than a metre - a distinction the university first gained in 1985 and lost in 1990.

How small is the writing? The letters in the words are assembled from subatomic sized bits as small as 0.3 nanometers, or roughly one third of a billionth of a metre.

The researchers encoded the letters S and U (as in Stanford University) within the interference patterns formed by quantum electron waves on the surface of a sliver of copper. The wave patterns even project a tiny hologram of the data, which can be viewed with a powerful microscope.

"We miniaturised their size so drastically that we ended up with the smallest writing in history," said Hari Manoharan, assistant professor of physics at Stanford University who directed the work of physics graduate student Chris Moon and other researchers.

The quest for small writing has played a role in the development of nanotechnology for 50 years, beginning decades before "nano" became a household word.

During a now-legendary talk in 1959, the remarkable physicist Richard Feynman argued that there were no physical barriers preventing machines and circuitry from being shrunk drastically. He called his talk "There's Plenty of Room at the Bottom."

Feynman offered a $1,000 prize for anyone who could find a way to rewrite a page from an ordinary book in text 25,000 times smaller than the usual size (a scale at which the entire contents of the Encyclopedia Britannica would fit on the head of a pin).

He held onto his money until 1985, when he mailed a cheque to Stanford graduate student Tom Newman, who, working with electrical engineering professor Fabian Pease, used electron beam lithography to engrave the opening page of Dickens' A Tale of Two Cities in such small print that it could be read only with an electron microscope.

That record held until 1990, when researchers at a certain computer company famously spelled out the letters IBM by arranging 35 individual xenon atoms.

Stanford researchers described how they have created letters 40 times smaller than the original prize-winning effort and more than four times smaller than the IBM initials.

Manoharan seeks to apply the "bottom-up" approach of atomic and molecular manipulation to a variety of outstanding problems in science and technology. The effort is interdisciplinary in nature, centering on physics and engineering but involving ideas, techniques, and conundrums from other fields such as chemistry, biology, materials science, and information technology.

The primary experimental apparatus for these investigations are custom-built low-temperature scanning probe microscopes capable of both studying and controlling matter at atomic length scales, said a Stanford release.

The process was described online in Nature Nanotechnology.