IBM researchers for the first time have succeeded in imaging how charge is distributed inside a single molecule, which is a fundamental research breakthrough as scientists try to miniaturise circuitry to the nanometer scale.
IBM is studying molecular structures when put on artificial surfaces so functional molecules in the future can be used as switches or transistors, said Fabian Mohn, an IBM researcher. IBM used advanced microscopy tools and techniques to image how charge is redistributed and arranged when chemical bonds are formed between atoms and molecules on surfaces.
The research breakthrough is a step ahead in understanding, controlling and tweaking molecular structures in electrical devices, Mohn said. For example, there may be a molecule with desirable properties to separate photons into positive and negative charges in each direction, which could help solar cells more effectively convert light to electricity.
The breakthrough is also a step forward in understanding the efficiency of a molecular structure as a switch, diode or transistor, said Michael Crommie, a professor of physics at the University of California and a faculty researcher at Lawrence Berkeley National Laboratory. He was not involved in the IBM research.
"Some people think it's interesting to use molecules as building blocks for electrical devices," Crommie said. "One of the troubles is to figure out how to put molecules, and to do what we want them to do, on surfaces. Many people are working on this."
IBM's technique is a diagnostic tool that allows researchers to better characterise small structures, Crommie said. Molecules are assemblies of atoms in particular configurations connected by chemical bonds, and behave differently depending on the environment. Electrons hold the atoms together and give molecules all of their properties.
There are infinite ways molecular systems can behave, and researchers want to be able to predict molecular behaviour on surfaces and tweak structures, Crommie said. For example, IBM's tool could help researchers in Crommie's lab create more effective graphene devices through modifications at an atomic level. Crommie wants to be able to modify the graphene by adding or removing charge, or see how graphene changes the behaviour of a molecule.
IBM has been conducting its own research on graphene, last year showing a graphene transistor that can execute 155 billion cycles per second, which was about 50 percent faster than previous experimental transistors shown by the company's researchers. Electron flow is considered to be faster on graphene transistors than conventional transistors, which enables faster data transfers between chips.
However questions remain on whether molecules are feasible as building blocks for semiconductors. It's also hard to predict the ultimate outcome of IBM's breakthrough, and years of research and experimentation are required to figure out whether molecular structures perform rationally in a synthetic environment, Crommie said.
"This is fundamental research. It's not like they are optimising a process that already exists. They are looking at new material combinations that are not being used in the industry. It's not something that's close to production," Crommie said.
IBM's Mohn said the next step could be to build on the technique further and to connect molecules, and also attach molecules to metal as they build nano-scale devices. The company's ultimate goal is to advance the technology to build electronic devices, but only time will tell where the research goes.
"It's like quantum computing. The idea is in principal it should be useful, but we are not there yet with direct applications," Mohn said.
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