Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory have made a groundbreaking discovery in the field of 2D semiconductor materials. By studying stacked monolayers of tungsten diselenide (WSe2) and tungsten disulfide (WS2), the team discovered that electrons play a crucial role in facilitating rapid heat transfer between the layers.
The layers in question are not tightly bonded to one another, yet the team found that electrons provide a bridge between them, allowing for efficient energy transfer. According to Archana Raja, a scientist at Berkeley Lab who led the study, “Our work shows that we need to go beyond the analogy of Lego blocks to understand stacks of disparate 2D materials, even though the layers aren’t strongly bonded to one another. The seemingly distinct layers, in fact, communicate through shared electronic pathways, allowing us to access and eventually design properties that are greater than the sum of the parts.”
The study, which was recently published in Nature Nanotechnology, combines insights from ultrafast, atomic-scale temperature measurements and extensive theoretical calculations. The team used a technique known as ultrafast electron diffraction (UED) to measure the temperatures of the individual layers while optically exciting electrons in just the WSe2 layer.
This groundbreaking research has implications for the future of energy dissipation in electronic devices. Aditya Sood, co-first author of the study and currently a research scientist at Stanford University, explains, “We were curious about how electrons and atomic vibrations couple to one another when heat flows between two materials. By zooming into the interface with atomic precision, we uncovered a surprisingly efficient mechanism for this coupling.”
The team fabricated the devices using a perfected technique of using Scotch tape to lift off crystalline monolayers of the semiconductors, each less than a nanometer in thickness. Using polymer stamps aligned under a home-built stacking microscope, these layers were deposited on top of each other and precisely placed over a microscopic window to enable the transmission of electrons through the sample.
This discovery opens up new possibilities for the design and development of 2D semiconductor materials and their potential applications in the field of energy dissipation. As Raja puts it, “The seemingly distinct layers, in fact, communicate through shared electronic pathways, allowing us to access and eventually design properties that are greater than the sum of the parts.”