Worlds smallest molecular transistor reboots Moore’s Law

WHY THIS MATTERS IN BRIEF

Scientists have demonstrated a new 0.167nm transistor.

It’s no secret that companies like Intel have been finding it increasingly difficult and, perhaps more pertinently, costly to keep pace with the expectations of Moore’s Law so it came as no surprise when in early 2016 a consortium representing the world’s largest semi-conductor company’s announced they’d no longer be beholden to it, choosing instead to follow a new industry agreed ITRS (International Technology Roadmap for Semiconductors) roadmap.

But while these companies were writing Moore’s Law into the history books a new 3D molecular computing breakthrough, which could shrink transistors from todays best of breed 7nm to just 0.167nm, could offer Moore’s Law a much needed shot in the arm. And, while many of us might think that accelerating computing price-performance returns, the very principle on which Moore’s Law is founded, are just the result of new developments in integrated circuitry the fact is that integrated circuits are the fifth, not the first, computing paradigm – the others being Electromechanical systems, then Relays, then Vacuum Tubes, then Transistors then, finally to todays Integrated Circuits. 3D molecular computing is increasingly looking like it will be the sixth.

Chip manufacturers have struggled to keep pace with Moore’s Law, which dictates that processing power will double every 18 to 24 months by doubling of the number of transistors they can fit on a chip not because we lack the engineering skill but because the costs of building and fitting out new fabrication plants is increasingly prohibitive.

The most advanced chips we have today are based on 7nm technology but recently scientists from the Freie Universität of Berlin, the NTT Basic Research Laboratories, Japan and the US Naval Research Laboratory have demonstrated a transistor that’s comprised of just a single molecule. Surrounded by just 12 atoms, it is likely to be the smallest possible size for a transistor – and the absolute hard limit for Moore’s Law.

Fig 1. The new molecular transistor

The transistor is made of a single molecule of Phthalocyanine surrounded by ring of 12 positively charged Indium atoms placed on an indium arsenide crystal. Each indium atom is 167 picometres in diameter, which makes them 0.167nm wide or 42 times smaller than the very smallest circuits currently possible. By comparison a strand of human hair at 100,000nm thick is about 600,000 times wider than the atoms surrounding the new transistor, a red blood cell is a 36,000 times bigger at 6,000nm and a strand of DNA is 15 times bigger at 2.5nm.

The new transistor represents a giant leap forward towards making Quantum Computing a mainstream reality and was made possible using a scanning tunnelling electron microscope to place atoms in exact positions and control the electron flow through the gate. Typically scientists working to this atomic scale have struggled to reliably control the flow of electrons, which are difficult to contain and can jump outside of the transistor rendering it useless.

The international team of researchers also discovered unexpected behaviour from the transistor. The orientation of the molecule of Phthalocyanine – an organic molecule typically used in dyes – at the heart of the transistor is affected by charge and its orientation could be changed by altering its charge, leading to more than a simple on-off switch-like state as seen in traditional transistors.

The work proves that precise control of atoms to create a transistor smaller than any other quantum system available is possible and opens the door to further research into harnessing these tiny transistors for computers and systems with orders of magnitude more processing power than today’s machines.