The Light of Nano Diamonds, Discovered by UNIST

Professor Kwon Oh-hoon's Team Develops High-Resolution Cathodoluminescence Detection Method

Ulsan National Institute of Science and Technology (UNIST) has developed a high-resolution cathodoluminescence detection technique based on transmission electron microscopy. (From left, Researcher Yejin Kim, Professor Oh-Hoon Kwon)

[Asia Economy Yeongnam Reporting Headquarters, Trainee Reporter Lee Seryeong] Researchers at Ulsan National Institute of Science and Technology (UNIST) have developed an analytical method that detects light emitted by nanodiamonds using an atomic-resolution microscope.

On the 28th, they announced that they proposed an advanced image processing analysis technique comparable to the scanning transmission electron microscopy-based technology published by a French research team in July this year.

Previously, only the luminescence phenomenon of ensembles consisting of multiple nanodiamonds could be detected, resulting in low sensitivity to distinguish the optical properties of individual particles. Now, not only nanodiamonds but also next-generation semiconductor materials that can replace silicon can be analyzed.

The research team led by Professor Kwon Oh-hoon of the Department of Chemistry at UNIST developed a technology to analyze the luminescent properties and charge carrier movement within materials such as wide band gap (WBG) materials like nanodiamonds.

The research was conducted with support from the Samsung Future Technology Development Foundation, and the results were published on December 13 local time in the world-renowned journal ‘ACS Nano.’

The band gap refers to the difference in energy bands that electrons can occupy, indicating the energy level difference between levels where electrons exist and those where they do not within a material.

Compound semiconductors with wide energy level characteristics are emerging as materials for next-generation semiconductors and quantum light sources, drawing attention to wide band gap materials.

Wide band gap materials are more resistant to high temperatures and high pressures than silicon, but their special physical properties with wide band gaps made it difficult to analyze their characteristics using conventional spectroscopic methods.

Professor Kwon’s team employed a new analytical method combining a cathodoluminescence detector with a high-resolution transmission electron microscope, which shoots an electron beam at the material to observe its structure at the atomic level.

Schematic diagram of photoluminescence characteristics analysis of nanodiamonds using transmission electron microscopy.

The high-energy electron beam of the transmission electron microscope can excite electrons in wide band gap materials to higher energy states, enabling luminescence characteristic analysis.

When electrons fall from the excited state to the ground energy state, light is emitted, and this information is transmitted to the cathodoluminescence detector.

The research team analyzed nanodiamonds, considered next-generation quantum light source materials, using this technology.

Inside nanodiamonds, there are multiple diamond NV centers, fine structures that can be used as light sources for quantum computers or information communication, and the team revealed the electron movement and the time required between these fine structures.

The team explained that this was possible thanks to possessing Korea’s only 4-dimensional ultrafast transmission electron microscopy technology, capable of capturing phenomena occurring instantaneously within very small materials.

This technology irradiates the electron beam in picosecond (10^-12 seconds) intervals, allowing it to read phenomena occurring in extremely short moments, such as electron movement within materials.

By narrowing the beam irradiation area very finely, it can separate and measure luminescence phenomena down to every corner of a single nanodiamond particle, which is much smaller than the thickness of a human hair.

First author Researcher Kim Ye-jin said, “The transmission electron microscopy-based analytical method allows observation deep inside the material.”

Professor Kwon Oh-hoon stated, “It can also contribute to the analysis of characteristics of ultra-fine luminescent materials such as quantum dots and van der Waals heterojunction materials, as well as the development of new nano-optical devices.”

This content was produced with the assistance of AI translation services.