QST develops microscope achieving both world-leading resolution and high precision

A research group consisting of Researcher Kohei Yamamoto and Senior Principal Researcher Jun Miyawaki from the National Institutes for Quantum Science and Technology (QST), Assistant Professor Hakuto Suzuki from the Frontier Research Institute for Interdisciplinary Sciences at Tohoku University, and their colleagues has successfully used the resonant inelastic X-ray scattering (RIXS) instrument "2D-RIXS" installed at NanoTerasu to visualize the behavior of electrons in materials with a spatial resolution of one micrometer or less for the first time in the world. Miyawaki commented: "Until now, it was difficult to achieve both high precision (energy resolution) and positional information (spatial resolution) simultaneously. We were able to develop the 2D-RIXS microscope by back-calculating the spatial information of X-ray photons. This technology can contribute to the development of a wide range of solid-state materials, including those for spintronics." The findings were published in the Journal of Synchrotron Radiation.

In 2024, QST independently developed a 2D-RIXS instrument with the world's highest energy resolution, and it was made available to a wide community of researchers starting in March 2025. Meanwhile, as research advances on increasingly miniaturized semiconductor devices and on quantum materials in which inhomogeneity plays a key role, it has become essential to know not only "what kind of electronic state exists" but also "where exactly in the sample that state is located."

To achieve spatial resolution without sacrificing ultrahigh energy resolution, the research group fundamentally re-examined the operating principle of the 2D-RIXS instrument. In the 2D-RIXS setup, signals collected from the entire sample (when irradiated with x-rays) are added together to boost intensity in pursuit of ultrahigh energy resolution. The group focused on the fact that before addition, each individual data point also contains information about where in the sample the signal originated. Building on this insight, they carried out painstaking, persistent verification involving spatial resolution evaluation and precise control of the optical system to establish a method for tracing the spatial origin of each individual X-ray photon. These efforts led to simultaneous achievement of ultrahigh energy resolution and high spatial resolution, which is a combination previously thought impossible.

Yamamoto said, "I engaged in a great deal of repeated trial and error to be able to calculate positional information with good accuracy and finally managed to make it work."

In practice, the group measured a fine pattern in the shape of the NanoTerasu logo, fabricated as a nickel thin film on a silicon substrate, using X-ray energy conditions that selectively extract information on nickel's 3D electrons. The group demonstrated that the pattern could be mapped with high precision at a spatial resolution of 1 micrometer.

The new technology is available through NanoTerasu's shared-use experiment program. Since it enables measurements of diverse elementary excitations—charge, orbital, lattice, and spin of electrons—with unprecedented precision, it is expected to make significant contributions to the development of next-generation devices in the future.

Journal Information
Publication: Journal of Synchrotron Radiation
Title: 2D-RIXS: resonant inelastic X-ray scattering microscopy with high energy and spatial resolutions
DOI: 10.1107/S1600577526000573