Molecular breakthrough replaces transistors

HP researchers today unveiled molecular-scale computing technology that could replace transistors in next-generation devices.

In a paper published in the Journal of Applied Physics, three members of HP Labs' Quantum Science Research (QSR) group outlined a "crossbar latch" which provides the signal restoration and inversion required for general computing without the need for transistors.

The technology could result in computers that are thousands of times more powerful than those in existence today, HP claimed. The company has been working on the technology since it filed patents back in 2001.

"We are reinventing the computer at the molecular scale," said Stan Williams, HP senior fellow and QSR director, and one of the authors of the paper.

"The crossbar latch provides a key element for building a computer using nanometre-sized devices that are relatively inexpensive and easy to build."

QSR works on nanoscale electronic devices that HP predicts will first supplement, and "someday perhaps replace", silicon technology, which is expected to reach its physical limits in about a decade.

QSR said that it is also working to determine how such tiny devices, thousands of which could fit across the diameter of a human hair, could be mass-produced commercially.

The crossbar latch consists of a single wire acting as a signal line, crossed by two control lines with an electrically switchable molecular-scale junction where they join.

By applying a sequence of voltage impulses to the control lines and using switches oriented in opposite polarities, the latch can perform the 'not' operation which, along with 'and' and 'or', is one of the three basic operations that make up the primary logic of a circuit and are essential for general computing.

In addition, it can restore a logic level in a circuit to its ideal voltage value allowing a designer to chain many simple gates together to perform computations.

Standard semiconductor circuits require three-terminal transistors to perform the 'not' operation and restore signals.

However, it is generally believed that transistors will not be able to shrink to the size of a few nanometres and remain operable, according to HP.

"Transistors will continue to be used for years to come with conventional silicon circuits," said Phil Kuekes, senior computer architect at QSR, and one of the paper's authors.

"But this could someday replace transistors in computers, just as transistors replaced vacuum tubes and vacuum tubes replaced electromagnetic relays before them."

Duncan Stewart, a QSR scientist and the paper's third author, added: "We have previously demonstrated that we could make a working memory with molecular-scale junctions and logic devices that could perform simple logic operations such as 'and' and 'or'.

"With the crossbar latch, we now have the final component theoretically needed for performing the multiple processing steps required for useful computing at the nanoscale."

The research on the crossbar latch was partially supported by the Defense Advanced Research Projects Agency.