Possibility of replacing gold nano circuit device by solving the rust problem of copper A crystal photograph showing an ultra-smooth surface at the level of an open monoatomic layer, the grains at the interface show the roughness of one particle. 2022.03.16 /News 1
Reporter Seung-Jun Kim = Even if the surface looks smooth, it is jaggedly rough when viewed at the atomic level. When the surface of the copper thin film was made smooth with an error of one atom layer thickness, it became less likely to rust.
The Ministry of Science and ICT held a briefing on the 15th to introduce the results of the research team of Professors Se-young Jeong, Professor Kim Young-min, and Professor Kim Seong-gon.
The research team made an ultra-smooth copper thin film with a roughness equivalent to that of a monoatomic layer in previous research. Surface roughness refers to the uneven height difference of the surface of the thin film, and the thin film made by the research team showed a roughness of 0.2 nm. This is the level of roughness on the level of one atom.
Professor Jeong Se-young of Pusan National University said that the difference between a flat surface and a non-flat surface is that it is difficult for electrons to move in a straight line, such as electrons being scattered and reflected from the internal boundary. explained that the nature of the
The research team observed the ultra-flat copper thin film exposed to air for one year with a high-resolution transmission electron microscope, etc.
As a result, oxidation at the level of one atom was not observed. In general, when copper is exposed to air for a long time, it combines with oxygen to form oxides and rusts.
To examine this theoretically, the researchers also calculated the change in energy for oxygen to enter the copper interior. When the surface roughness is two or more atomic layers, oxygen penetration into the copper proceeds easily, whereas when the surface is perfectly flat or a monoatomic layer, oxidation does not occur at room temperature because very large energy is required for oxygen penetration.
The energy required for oxygen to penetrate into copper varies depending on the number of surface atomic steps. Figure A shows through calculations that oxygen permeation is an endothermic reaction when the surface atomic step is one layer, and an exothermic reaction when there are two or more layers. Figure B shows that when oxygen occupies more than 50% of the flat copper surface, it has a self-regulating function to repel oxygen by itself. It is experimentally shown that this exists. 2022.03.16 /News 1
In addition, it was revealed that the oxygen present on the surface of the ultra-smooth thin film has a self-regulating function to inhibit oxidation by pushing out other oxygen from access when 50% of the sites where oxygen can exist are filled.
This study has the meaning of revealing the exact cause of oxidation of copper used in industry and opening the possibility of economically replacing gold used in nanocircuits with copper thin films.
In addition, it has great significance in that it has developed its own technology to grow an atom-level thin film, and the replacement of gold with copper having high electrical conductivity may contribute to economic advantages and miniaturization of equipment.
Professor Sei-Young Jeong said that this research result was the first case in the world to identify the origin of copper oxidation at the atomic level, and opened up the possibility of manufacturing unchanging copper.
This achievement, which was carried out with the support of the Ministry of Science and ICTs individual basic research and group research support project, was
Professor Jeong Se-young of Pusan National University is giving a briefing on research results on the working principle of copper oxidation in the press room of the Ministry of Science and ICT at the Sejong Finance Center in Sejong City on the morning of the 15th. 2022.03.16 /News 1
