Elucidation of Copper Oxidation Mechanism... Paving the Way for Nano-Circuit Gold Replacement

Professor Jeong Se-young of Pusan National University and domestic and international research teams
Successful fabrication of ultra-flat copper thin films with monolayer-level roughness
Confirmed that it does not oxidize and can replace gold coating in industrial fields

Simulation image of ultra-flat copper thin film with monolayer-level roughness. Image provided by the Ministry of Science and ICT

[Asia Economy Reporter Kim Bong-su] Domestic researchers have, for the first time in the world, elucidated the principle of copper oxidation when exposed to air. They also confirmed that an ultra-flat copper thin film composed of a single copper atom does not oxidize, opening the door to replacing the expensive gold used in nano circuits with affordable copper.

The Ministry of Science and ICT announced on the 17th that Professor Jeong Se-young of Pusan National University, Professor Kim Young-min of Sungkyunkwan University, and Professor Kim Sung-gon of Mississippi State University jointly identified the oxidation mechanism of copper using an ultra-flat copper thin film with atomic-layer-level roughness, similar to how a brick wall represents a single layer of height, through theory and experiments for the first time in the world. Atomic-layer-level roughness means that the thin film is made by stacking atoms one by one in an orderly manner like building a brick wall, and the uneven height on the completed thin film surface is called surface roughness. This research result was published in the international journal Nature.

The research team implemented an ultra-flat copper thin film with atomic-layer-level roughness using a self-developed thin film growth device (ASE). In particular, since the ultra-flat thin film can be manufactured in large sizes and is cost-effective, it is expected to replace the expensive equipment used so far.

The team exposed the copper thin film produced in this way to air for one year while observing it using high-resolution transmission electron microscopy and other methods. As a result, neither the natural oxide film typically observed on copper surfaces nor oxidation at the atomic single-layer level was detected.

Calculations of the energy change for oxygen to penetrate into copper revealed that when the surface roughness is two atomic layers or more, oxygen penetration into copper proceeds easily. However, when the surface is perfectly flat or at the atomic single-layer level, a very large amount of energy is required for oxygen penetration, so oxidation does not occur at room temperature. They also confirmed a self-regulating function that suppresses oxidation by repelling additional oxygen once 50% of the oxygen-occupiable sites on the ultra-flat thin film surface are filled.

The research team stated, "It is significant that we accurately identified the cause of copper oxidation used across industries and economically created an opportunity to fully replace gold used in nano circuits with copper thin films." They added, "Developing the technology to grow thin films at the atomic single-layer level itself is highly meaningful, and replacing gold with copper, which has high electrical conductivity, can contribute to economic benefits and equipment miniaturization."

Professor Jeong Se-young said, “This research achievement is the world’s first case to elucidate the origin of copper oxidation at the atomic level,” and emphasized, “It has opened the possibility of manufacturing unchanging copper.”

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