Researchers have shown that the metal particles in memristors and “resistive random access memory”, or RRAM – computer components that combine logic and memory functions – do not stay put in one place as previously thought. The finding has broad implications for the semiconductor industry and could pave the way for smaller, more efficient chips. “Most people have thought you can’t move metal particles in a solid material,” said lead researcher Wei Lu, associate professor of electrical and computer engineering at University of Michigan in the US. “In a liquid and gas, it’s mobile and people understand that, but in a solid we don’t expect this behaviour. This is the first time it has been shown,” Lu added.
The results could lead to a new approach to chip design – one that involves using fine-tuned electrical signals to lay out integrated circuits after they are fabricated. And it could also advance memristor technology, which promises smaller, faster, cheaper chips and computers inspired by biological brains in that they could perform many tasks at the same time. Researchers exposed the metal layer of their memristor to an electric field.
They observed the metal atoms becoming charged ions, clustering with up to thousands of others into metal nanoparticles, and then migrating and forming a bridge between the electrodes at the opposite ends of the dielectric material. They demonstrated this process with several metals, including silver and platinum. And depending on the materials involved and the electric current, the bridge formed in different ways. “We succeeded in resolving the puzzle of apparently contradicting observations and in offering a predictive model accounting for materials and conditions,” said Ilia Valov from Electronic Materials Research Center Julich in Germany. “Also the fact that we observed particle movement driven by electrochemical forces within dielectric matrix is in itself a sensation,” he added.