Researchers have used SLAC’s experiment for ultra fast
electron diffraction, one of the world’s fastest electron cameras to take
snapshot of s three-atom thick layer of a promising material as it wrinkles in
response to a laser pulse. Understanding these dynamic ripples could provide
crucial clues for the development of the next generation solar cells.
The breakthrough, could take material science to a whole new
level. It was made possible with SLAC’s instruments for ultrafast electron
diffraction (UED), which uses energetic electrons to take snapshots of atoms
and molecules on timescale as fast as 100 quadrillionths of a second.
“This is the first published scientific result with our new
machine,” said scientist Xijie Wang. “it showcases the method’s outstanding combination of atomic resolution,
speed and sensitivity.”
Extraordinary Material properties in Two Dimensions.
Monolayers contains just a single layer of molecules. In this
form they can take on new and exciting properties such as superior mechanical
strength and an extraordinary ability to conduct electricity and heat. The
question is, how do these monolayers acquire their unique characteristics? Until
now, researchers only had a limited view of the underlying mechanisms.
“The functionality of 2-D material critically depends on how
their atoms move,” said SLAC. However, no one has ever been able to study these
motions on atomic level and in real time before. Our engineering is a crucial
step towards the next-generation devices from single-layer materials.
The research team looked at molybdenum, which is widely used
as a lubricant but takes on a number of interesting behaviors when it in single layer form ……more than
150,000 times thinner than a human hair.
For example, the monolayers form is usually an insulator, but
when stretched, it can become electrically conductive. This switching behavior
could be used in thin, flexible electronics and to encode information in data
storage devices.
Electron camera reveals ultra-fast motions.
Previous analyses showed that single layers of molybdenum
disulfide have a winkled surface. However, these studies only provide a static
picture. The new study reveal for the first time how surface ripples form and
evolve in response to laser light.
The team used ultra-short laser pulse to excite motions in
the material, which cause scattering pattern to change over time.
Combined with theoretical calculations, these data show how
light pulse generates wrinkles that have large amplitudes……More than 15
percent of the layer’s thickness…..and develop extremely quickly, in about a
trillionth of a second, which is the very first time someone has visualized the ultra-fast atomic motions, said Lindenberg.
Once scientists understand monolayers of different
materials, they could begin putting them together and engineer mixed materials
with completely new optical, mechanical, electronic and chemical properties.
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