A team of researchers led by Prof John Boland from Trinity College-based research centre AMBER have made a breakthrough that could change the way materials are designed and used in everyday devices.
Prof John Boland, with Dr Xiaopu Zhang and Prof Adrian Sutton from Imperial College London, and Prof David Srolovitz from University of Pennsylvania, showed that the granular building blocks in copper can never fit together perfectly, but are rotated causing an unexpected level of misalignment and surface roughness.
Electrical, thermal and mechanical properties are controlled by how the grains in a material are connected to each other. Until now, it was thought that grains, made up of millions of atoms, pack together likes blocks on a table top with small gaps.
Prof Boland and his team have shown for the first time that nano-sized grains in copper actually tilt up and down to create ridges and valleys within the material. Nanocrystalline metals such as copper are widely used as electrical contacts and interconnects within integrated circuits.
This new understanding at the nanoscale could lead to the construction of more efficient devices, by reducing resistance to current flow, thus increasing battery life.
“Our research has demonstrated that it is impossible to form perfectly flat nanoscale films of copper and other metals,” said Prof Boland.
“The boundary between the grains in these materials have always been assumed to be perpendicular to the surface. Our results show that in many instances these boundaries prefer to be at an angle, which forces the grains to rotate, resulting in unavoidable roughening.
“This surprising result relied on our use of scanning tunneling microscopy which allowed us to measure for the first time the three-dimensional structure of grain boundaries, including the precise angles between adjacent grains.
“More importantly, we now have a blueprint for what should happen in a wide range of materials and we are developing strategies to control the level of grain rotation. If successful we will have the capacity to manipulate material properties at an unprecedented level, impacting not only consumer electronics but other areas such as medical implants and diagnostics. This research places Ireland yet again at the forefront of material innovation and design.”
The research was published in the academic journal Science, and was supported by industry partner Intel.
The AMBER material science research centre is funded by Science Foundation Ireland.
Prof Boland is Dean of Research at Trinity, a fellow of Trinity College and a fellow of the American Association for the Advancement of Science. In 2011 he was the Laureate of the 11th ACSIN Nanoscience Prize and was awarded a prestigious ERC Advanced Grant in 2013.
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