Holographic electron microscope has 0.47nm resolution

Holographic electron microscope has 0.47nm resolution

Technology News |
By Nick Flaherty

Hitachi has developed image acquisition and defocusing correction techniques to observe atomic-scale magnetic fields at a resolution of 0.47nm using a holographic electron microscope

The researchers in Japan uses electron holography microscopy to visualize magnetic fields in materials at atomic resolution and developed techniques to achieve a groundbreaking resolution of 0.47 nm when imaging magnetic atomic lattices in a crystal. The previous record resolution was 0.67nm, also set by Hitachi in 2017.

The team has scientists from Hitachi, Kyushu University, RIKEN, and HREM Research developed image acquisition technology and defocus correction algorithms to visualize the magnetic fields of individual atomic layers within a crystalline solid.

Atom arrangement and electron behaviour are among the most critical factors that dictate a crystalline material’s properties and the orientation and strength of magnetic fields at the interface between different materials or atomic layers are particularly important.

The results were published in Nature.

The key is a system to automate the control and tuning of the device during data acquisition, significantly speeding up the imaging process to a speed of 10,000 images over 8.5 hours. Then, by performing specific averaging operations with these images, they minimized noise to obtain much clearer images containing distinct electric field and magnetic field data.

The next challenge addressed was the correction for minute defocusing, which caused aberrations in the acquired images. This technique was able to correct for defocusing due to minor focus shifts by analyzing reconstructed electron waves so that the resulting images were free of residual aberrations, making the positions and phases of atoms easily discernible with magnetic field.

“The idea of post-image-capture correction of aberrations we employed is exactly the same as that which had motivated Dr. Dennis Gabor to invent electron holography in 1948. Until now, however, there had been no technological implementations for such automated correction in off-axis electron holography,” explains Chief Researcher Toshiaki Tanigaki from Hitachi.

The team performed electron holography measurements on samples of Ba2FeMoO6, a layered crystalline material in which adjacent atomic layers have distinct magnetic fields. Upon comparing their experimental results with simulations, they confirmed that they surpassed the previously set record, managing to observe the magnetic fields of Ba2FeMoO6 at a resolution of 0.47 nm.

“This result opens doors to direct observations of the magnetic lattices in specific areas, such as interfaces and grain boundaries, in many materials and devices,” said Tanigaki. “Our study marks the first step towards investigating many veiled phenomena whose existence can be revealed by electron spin configurations in magnetic materials.”

“Our atomic-resolution holography electron microscope will be used by various parties, contributing to advances in a wide range of fields ranging from fundamental physics to next-generation devices.”



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