Breaking the single-atom limit in atomic manipulation

The ultimate building blocks of matter are atoms and molecules. If we can control these we can truly build from the bottom up, for example, a computer made of atomic-scale components that would fit into the palm of your hand yet be more powerful than today's supercomputers. In 1986 the Nobel prize was won for the invention of a microscope that can image individual atoms and molecules, the scanning tunnelling microscope (STM). But more than that, in 1989 that microscope was used to assemble a man-made structure atom-by-atom with atomic precision; a 35 Xenon atom advert for IBM. Since then many great strides have been taken in the quest for ultimate atomic control, including breaking and making individual chemical bonds, constructing a single molecule transistor and even constructing logic gates out of carbon-monoxide molecules. So why, in the intervening 22 years, has such atomic scale engineering not become common place in modern technology? There are of course many technical challenges to working on this atomic level, for example, at the atomic scale everything sticks to everything and even at room temperature your IBM advert will boil off into space. But perhaps the most challenging limitation is not due to a fundamental problem with the quantum physics that governs atoms and molecules, but is instead the construction process itself: all these exquisite structures were built one atom at a time. That is quite a manufacturing bottleneck!

This experimental proposal aims to explore a new way of controlling multiple atoms and molecules with the scanning tunnelling microscope - nonlocal atomic manipulation. Instead of manipulating only the atom that is directly in the microscope's sights, leading to the one-atom-at-a-time limit, here we'll spread the effect of the microscope (specifically its injected electric current) across a surface over distances of 10's of manometers. This nonlocal process allows thousands of individual molecules to be manipulated simultaneously. Many critical questions remain to be answered if this new mode of manipulation is to have any promise of constructing extended structures with atomic precision: what roles do the molecules and the surface play in the nonlocal process? Is there a difference to what happens for a molecule directly under the microscope (as in conventional atomic manipulation) and a molecule some distance remote? How is the electrical current transported from microscope to distant target molecules? And how general a process is this? By answering these questions we'll be closer to transforming atomic manipulation from an elegant laboratory technique to a manufacturing tool for creating (relatively!) large scale but atomically precise structures.

A number of groups have been identified for whom this fundamental physics proposal will benefit society and the economy in the next 10-20 years.

General Public

There is an on-going public debate about the merits and dangers of nanoscience and technology. For example the 'grey-goo' theory that self-replicating nanomachines consume all the matter of the Earth through building more of themselves. Issues surrounding the environmental fate of nanoparticles, toxicology and occupational risk have all been highlighted in public debate scenarios. These are global issues as we will all be users of products containing nanomaterials, regardless of the material's origin and their disposal after use. Through this research and using its outcomes, the public will be more informed of the benefits of studying the fundamental properties of nanoscience. This work, although fundamental in nature could lead (10-20 years) to electronic devices working faster than current silicon based technologies and with less demand for energy.

Scanning probe microscope manufacturers:

The top three (world wide) research grade scanning probe microscopes companies, SPECS-Nanonis, Omicron and RHK Technology have recently changed or plan to change to fully digital control systems. This allows almost unlimited control over the microscope and other integrated experimental equipment (e.g., magnetic field). The development of the fully-automated experiments as an outcome of this proposal will have direct impact on these companies as it will showcase the possibilities of this 'second generation' scanning probe microscope, as well as the potential to be built-in to the companies' software and so extend their capabilities.

Computing industry

The manufacture of an atomic-scale neuron in a silicon substrate will have a broad impact on the UK ICT sector. The global silicon semiconductor industry is facing a fundamental limitation to its continuing quest for top-down size reduction. Atomic-manipulation is at the heart of a drive towards bottom-up construction of atomic-scale computer components and in new designs of computer chip architectures such as quantum computers. Another possible replacement of conventional microchips is neural networks. Neural networks are the ideal candidate for creating artificial intelligence. This proposal's demonstration of a semiconductor artificial neuron will open a possible pathway to manufacturing arrays of artificial neurons in order to build a neural network and a new class of computing technology.

Skills

Although this First Grant is focused on the PI, this proposal will enable undergraduate projects and an associated PhD student to be exposed to the cutting edge techniques of atomic control over matter. The UK needs such trained scientists for this area to maintain its focus on long-term opportunities for innovation.