Controlling current at atomic levels will have limits

Jul 27, 2015 09:50 GMT  ·  By

Since semiconductor nanowires’ sizes have managed to reach three atoms in width, once you go down to single-atom thickness, you've pretty much hit dead end.

A team of researchers representing Paul-Drude-Institut für Festkörperelektronik (PDI) and the Freie Universität Berlin (FUB), Germany, the NTT Basic Research Laboratories (NTT-BRL), Japan, and the U.S. Naval Research Laboratory (NRL) managed to combine forces and build a minute transistor consisting of one single molecule of copper phthalocyanine molecule, a dozen indium atoms, and an indium arsenide backing material.

The new transistor abandons the old principle of controlling current by modulating the gate voltage and it instead adopts a field effect. Now the way to control current is by varying the gate distance to modulate electricity. The gate consisted entirely of just a few atoms.

Revolutionary, with limited immediate applicability

However, the test and research conditions aren't exactly what you'd usually find around yourself to actually enjoy gadgets and devices so small that need atom-sized transistors. The small transistor was developed in near-total vacuum, at a temperature barely above absolute zero. That's obviously not your average Earth atmosphere. The team used a highly stable scanning tunneling microscope (STM) to create a transistor consisting of a single organic molecule and positively charged metal atoms, positioning them with the STM tip on the surface of an indium arsenide (InAs) crystal.

Apparently, there is a major difference between a conventional semiconductor quantum dot - comprising typically hundreds or thousands of atoms - and the present case of a surface-bound molecule. The molecule adopts different rotational orientations, depending on its charge state.

Although it doesn't have any immediate applications except the semiconductor industry, the perfection and reproducibility offered by these STM-generated transistors will enable researchers to explore elementary processes involving current flow through single molecules at a fundamental level. Using this research, it will be easier for scientists to develop more advanced semiconductors and better process technologies in the entire IT industry.