Developing ultimate nanodevices through the understanding of a "single atom"

LANGUAGE ≫ Japanese

INAMI Eiichi

Specialized field: Nano-functional-materials/devices, Scanning probe microscopy, Single Atom/molecule manipulation, Optical Properties of Materials, surfaces/interfaces

For Details

Tiny particles called atoms make up everything around us. Air, water, and the human body all consist of these atoms. About 40 years ago, a revolutionary microscope was invented that could not only visualize atoms, which are invisible to the naked eye, but also manipulate them individually. This was the Scanning Probe Microscope (SPM). Professor Eiichi Inami is exploring the microscopic world using this specialized microscope as his key instrument, taking on the challenge of developing nanomaterials that could lead to innovations.

Atomic-level manufacturing to further advance microfabrication technology

From smartphones and electric vehicles to digital appliances, financial systems, and transportation infrastructure...Semiconductors serve as the key component driving the rapid advancement of digitalization. Professor Inami explains, "Through the dramatic evolution of semiconductor microfabrication technology, we have achieved higher performance, miniaturization, and improved energy efficiency across all systems." Smartphones are a prime example of this trend. The latest iPhone model contains 19 billion transistors. In other words, an incredible number of semiconductor components--so tiny that they are invisible to the naked eye--are densely packed into a device small enough to fit in the palm of your hand.

"Calculations that once took several days on large computers can now be performed instantly on smartphones. This is truly a gift of miniaturization."

"Atomic manipulation"--i.e., observing and moving individual atoms using a scanning probe microscope (SPM)*--holds great promise as a novel approach based on this principle to meet the growing demand for technological innovation. Professor Inami is working to advance this cutting-edge microfabrication technology. Using SPM, researchers are gaining deeper insights into material structures and properties at the single-atom level. This research not only enables the discovery of new material characteristics and functions but also facilitates the development of technologies that allow precise control over these properties.

"'Manufacturing at the atomic level' is a simple way to describe it. When you closely examine any material, you ultimately see an arrangement of atoms. We are trying to understand how different atom connections give rise to specific properties, and by deliberately altering these arrangements, we aim to discover new materials or find new characteristics of existing ones. Our goal is to utilize these insights to develop novel nanomaterials and realize high-functionality devices based on them."

*A microscope that can measure the shape and physical properties of a sample's surface at the atomic scale by tracing it with a sharp needle (probe) featuring a single atom at its tip. Unlike an optical microscope, it does not rely on lenses but instead consists of precision machinery and a monitor.

Unveiling still-unknown atomic properties to drive the development of ultra-high-performance devices

Professor Inami has made numerous globally impactful discoveries through his previous research using SPM. One such breakthrough is the finding that when a small amount of visible light is shone on graphite, which consists of carbon atoms, part of it transforms into a material (called diaphite), exhibiting properties intermediate between diamond and graphite. While carefully investigating this phenomenon, he successfully became the first in the world to directly observe, at the atomic scale, a photo-induced phase transition--a process in which a material's structure and properties change upon exposure to light--and elucidated its underlying mechanism. Furthermore, he discovered that the phase transition process varies significantly depending on the wavelength of light, demonstrating that light tuning enables atomic-level control over the transition. These findings are expected to accelerate the development of new materials.

"Currently, while investigating the properties of this diaphite, we are also tackling the challenge of microfabrication that combines light and atomic manipulation. If this technology is realized, it will enable the precise arrangement of diaphite at the atomic level, similar to electronic circuits. Through this research, we aim not only to uncover the latent characteristics of diaphite but also explore how these properties can be intricately combined to create new functionalities and apply them to device development."

Nanoclusters--aggregates of multiple atoms--are known to exhibit dramatic changes in their properties depending on the number of constituent atoms. Professor Inami states that he and his team made a significant discovery while diligently conducting experiments to uncover hidden properties by precisely controlling the size of these nanoclusters at the single-atom level.

"When we arranged lead atoms one by one using the SPM probe, we discovered that when three atoms were placed nearby and a tiny current was applied, their positions shifted and then returned. In other words, we found that a cluster of three lead atoms can function as a switch at room temperature."

If a method can be developed to arrange these clusters at high density and reliably induce switching, it could pave the way for ultra-high-performance computers and devices.

Recently, he has been actively working on the development of new SPM-based devices. More than 40 years have passed since SPM was first developed at IBM's Zurich Research Laboratory in Switzerland, and performance improvements are now essential to keep pace with advancements in microfabrication technology. To address this, Professor Inami and his colleagues have devised a microscopy technique utilizing the pulsed voltage method. Pulsed voltage refers to a voltage waveform that rises sharply, remains for a short duration, and then drops sharply. His team is developing a novel approach that enables surface observation while applying a series of such pulses to the sample.

"With this new technology, we can not only observe the process of two atoms joining to form a molecule in more detail but also precisely measure the 'work function,' which is the minimum energy required to remove an electron from a material."

Expectations are growing for technological innovations that will further advance microfabrication technology.

Aiming to pioneer a new field through the combination of light and atomic manipulation

Professor Inami is currently working on atomic-scale manufacturing, utilizing a wide range of techniques such as material analysis, processing, and equipment development. However, his fascination with the microscopic world began when he was in junior high school.

"In science class, when I saw a diagram showing the 'structure of atoms,' where several spheres were attached, I couldn't help but wonder, 'How do we know it looks like this if we can't see it?'"

He went on to study in the Faculty of Science at university. By analyzing material structures using methods such as X-ray analysis, he intellectually understood the atomic structures. However, his desire "to see atoms directly with his own eyes" only grew stronger. Then, the long-awaited moment arrived.

"During my master's program, a professor showed me an 'image of atoms neatly arranged.' It was so real that I was surprised. I got really excited, thinking, 'Can you see atoms!?' This was an image captured by SPM, and I suddenly became very interested, realizing that I could do fascinating research using this microscope."

Although he specialized in astrophysics as an undergraduate and studied the optical properties of materials during his master's program, this experience led him to pursue atomic manipulation using SPM. Since then, he has been working on a wide range of research themes, from microscopic to macroscopic, using SPM as his key research tool. In 2018, he joined Kochi University of Technology to establish his unique research approach, integrating all of his previous experiences.

"I've been affiliated with various university laboratories and have conducted research cutting across the fields of SPM, optical properties of materials, and surface science. At KUT, I am pursuing research to pioneer a new field by integrating these three areas."

Currently, he collaborates with other universities on cutting-edge research, while also working with KUT faculty members in information science to integrate AI into theoretical calculations that predict material properties from atomic structures. Through this approach, he is developing technology to predict various functions more quickly and accurately. At the core of his ambition lies a consistent goal: "I want to create unprecedented new devices by freely combining atoms."

"When materials are miniaturized to the extreme, unusual properties known as 'quantum phenomena' can emerge. Applications of these phenomena are already being developed, for example, in quantum computers that can perform ultra-high-speed calculations. In other words, nanotechnology is not just about enhancing the performance of existing systems based on conventional principles, but rather about dramatically changing them through entirely new principles that have never existed before. I'm convinced that atomic-scale manufacturing is the fastest path to realize truly innovative devices."

Date of posting: February, 2025/ Date of interview: November, 2024