Three physicists from RIKEN have illustrated the flexibility of an ultrafast type of transmission electron microscopy to quantify sound waves in nanostructures.
A cutaway of the ultrafast transmission electron microscope (UTEM) that RIKEN researchers used to picture ultrahigh-frequency sound waves in a skinny silicon plate. The laser one the left gives two beams, one (higher beam) that interacts with the electron beam (inexperienced) of the microscope and the opposite (decrease beam) illuminates the pattern. Picture Credit score: © 2023 RIKEN Middle for Emergent Matter Science
This can assist establish a high-resolution imaging method that makes use of ultrahigh-frequency sound waves to picture buildings which are nanometers in measurement.
Ultrasound is usually utilized in clinics and hospitals to picture inner organs and infants within the womb. Usually, the sound waves used are a couple of millimeters in wavelength, so they may picture buildings right down to that stage.
Whereas such a decision is taken into account to be high-quality for medical imaging, physicists want to make the most of sound waves to picture buildings in supplies that measure round a couple of nanometers.
If we are able to use sound waves which have wavelengths of about 100 nanometers or so, we are able to use them for inspecting supplies, akin to discovering defects. However the sensitivity to small defects actually is dependent upon the wavelength.
Asuka Nakamura, Middle for Emergent Matter Science, RIKEN
This wants producing and detecting sound waves that encompass a lot smaller wavelengths (and thus larger frequencies). Making such high-frequency sound waves is relatively easy—ultrashort laser pulses have been utilized to supply them in metals and semiconductors for a lot of many years.
Nevertheless, detecting them is very tough because it wants creating detectors which have the potential to acquire a decision of nanometers in house and picoseconds in time.
At current, Nakamura, along with CEM collaborators Takahiro Shimojima and Kyoko Ishizaka, have illustrated the flexibility of a novel form of electron microscope for imaging such ultrahigh-frequency sound waves.
Notably, they utilized an ultrafast transmission electron microscope (UTEM) to detect sound waves produced by a 200-nm gap within the heart of an ultrathin silicon plate. A UTEM makes use of two laser beams with a slight delay between them.
One beam is liable for illuminating the pattern, whereas the opposite produces an ultrashort pulse of electrons within the microscope. This setup permits very quick timescales to be resolved.
Theoretically, when the trio simulated the waves and made a comparability of the simulations with experimentally achieved photographs, they found good settlement.
The standard of the pictures surpassed the crew’s expectations, thereby enabling them to execute Fourier-transform evaluation—a generally utilized mathematical analytic technique—on the pictures.
Earlier than performing these experiments, we didn’t intend to characterize the sound waves. However after taking the info, we seen they have been very lovely, and we may apply Fourier transformation. That was shocking for me.
Asuka Nakamura, Middle for Emergent Matter Science, RIKEN
At the moment, the scientists imply to investigate ultrafast magnetic and structural dynamics in solids induced by such nanometric sound waves using UTEM.
Journal Reference
Nakamura, A., et al. (2023) Characterizing an Optically Induced Sub-micrometer Gigahertz Acoustic Wave in a Silicon Skinny Plate. Nano Letters. doi.org/10.1021/acs.nanolett.2c03938.
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