A team of scientists, led by the Department of Energy’s (DOE’s) Oak Ridge National Laboratory, have developed a “nano brush” that is made from alternating crystal sheets with a high surface area. The scientists come from other DOE labs, Massachusetts Institute of Technology (MIT), University of South Carolina, and the University of Tennessee at Knoxville.
"These are major technical accomplishments and may prove useful in advancing energy and information technologies," said ORNL's Ho Nyung Lee, who led the study. "This is an excellent example of work that is only feasible with the unique expertise and capabilities available at national labs."
The multilayer crystal or “super crystal” has bristles that are grown freestanding on a substrate. The super crystals were synthesized by using pulsed laser epitaxy, which built up alternating layers of fluorite-structure cerium oxide (CeO2) and bixbyite-structure yttrium oxide (Y2O3). Using scanning transmission electron microscopy (STEM), former ORNL postdoctoral fellow Xiang Gao discovered atomically precise crystalline interfaces within the bristles.
ORNL's Jonathan Poplawsky measured samples from the bristles using atom probe tomography (APT) to see the distribution of CeO2 and Y2O3 within the nano brush. Says Poplawsky, “APT is the only technique available that is capable of probing the three-dimensional positions of atoms in a material with sub-nanometer resolution and 10 parts per million chemical sensitivity. APT clarifies the local distributions of atoms within a nanosized object and was an excellent platform for providing information about the 3D structure of the interface between the cerium oxide and yttrium oxide layers."
"This is a truly innovative way to build crystalline nanoarchitectures, providing unprecedented vertical interfaces that were never thought viable," said Lee. "You cannot achieve these perfect crystalline architectures from any other synthesis method. There are many ways to utilize interfaces, which is why 2000 Nobel Prize winner Herbert Kroemer said, 'the interface is the device.”
The nano brush is highly porous and because of its high surface area, it is able to maximize electronic and chemical reactions, like sensors, membranes, and electrodes. Lee said, "Indeed, these critical interfaces could form inside of nano brush architectures, making them more promising than conventional thin films in many technological applications. Their much greater surface area and larger number of interfaces -- potentially, thousands inside each bristle -- may prove a game-changer in future technologies in which the interface is the device."
The research is published in the journal, Nature Communications.