KRISS
-
An Electron Cloud Distribution Observed by the Scanning Seebeck Microscope
All matters are made of small particles, namely atoms. An atom is composed of a heavy nucleus and cloud-like, extremely light electrons.
Korean researchers developed an electron microscopy technique that enables the accurate observation of an electron cloud distribution at room-temperature. The achievement is comparable to the invention of the quantum tunneling microscopy technique developed 33 years ago.
Professor Yong-Hyun Kim of the Graduate School of Nanoscience and Technology at KAIST and Dr. Ho-Gi Yeo of the Korea Research Institute of Standards and Science (KRISS) developed the Scanning Seebeck Microscope (SSM). The SSM renders clear images of atoms, as well as an electron cloud distribution. This was achieved by creating a voltage difference via a temperature gradient.
The development was introduced in the online edition of Physical Review Letters (April 2014), a prestigious journal published by the American Institute of Physics.
The SSM is expected to be economically competitive as it gives high resolution images at an atomic scale even for graphene and semiconductors, both at room temperature. In addition, if the SSM is applied to thermoelectric material research, it will contribute to the development of high-efficiency thermoelectric materials.
Through numerous hypotheses and experiments, scientists now believe that there exists an electron cloud surrounding a nucleus. IBM's Scanning Tunneling Microscope (STM) was the first to observe the electron cloud and has remained as the only technique to this day. The developers of IBM microscope, Dr. Gerd Binnig and Dr. Heinrich Rohrer, were awarded the 1986 Nobel Prize in Physics.
There still remains a downside to the STM technique, however: it required high precision and extreme low temperature and vibration. The application of voltage also affects the electron cloud, resulting in a distorted image.
The KAIST research team adopted a different approach by using the Seebeck effect which refers to the voltage generation due to a temperature gradient between two materials.
The team placed an observation sample (graphene) at room temperature (37~57℃) and detected its voltage generation. This technique made it possible to observe an electron cloud at room temperature.
Furthermore, the research team investigated the theoretical quantum mechanics behind the electron cloud using the observation gained through the Seebeck effect and also obtained by simulation capability to analyze the experimental results.
The research was a joint research project between KAIST Professor Yong-Hyun Kim and KRISS researcher Dr. Ho-Gi Yeo. Eui-Seop Lee, a Ph.D. candidate of KAIST, and KRISS researcher Dr. Sang-Hui Cho also participated. The Ministry of Science, ICT, and Future Planning, the Global Frontier Initiative, and the Disruptive Convergent Technology Development Initiative funded the project in Korea.
Picture 1: Schematic Diagram of the Scanning Seebeck Microscope (SSM)
Picture 2: Electron cloud distribution observed by SSM at room temperature
Picture 3: Professor Yong-Hyun Kim
2014.04.04 View 12972 -
OLEV Safety Confirmed by International Standards
On September 19, KAIST announced that the electromagnetic (EM) field levels of its online electric vehicle (OLEV) measured in June and September of this year demonstrated verification of its safety.
Last June, the EM field level of OLEV installed at the Seoul Grand Park was measured by the Korea Research Institute of Standards and Science (KRISS) to test its harmfulness to human. The results were 0.5 ~ 61mG which is within the national and international standards of 62.5mG.
KRISS measured EM field levels on 22 spots on the side of and at the center of OLEV at a fixed distance (30cm) but variable heights (5cm~150cm) according to the national standard of measurement methods for electromagnetic fields of household appliances and similar apparatuses with regard to human exposure (IEC 62233).
In addition, another testing took place on September 13 following a request by National Assemblywoman Young-Ah Park, a member of the National Assembly’s Education, Science and Technology Committee, who has raised an issue on the safety of OLEV. This testing session was held by EMF Safety, Inc., an institution designated by Park, and it tested the EM field level of the same OLEV train that was tested in June.
As a result, the September measurements were well within the national and international standards with 0~24.1mG. The test was conducted under the presence of third party to produce a fair and objective result.
As reference, the EM field level results are well within the American IEEE electromagnetic field standards of 1,100 mG.
The September measurements were produced by Park’s recommendation of following the criteria specified in the measurement procedures of IEC 62110, “Electric and magnetic field levels generated by AC power systems to public exposure,” which were 15 measurements at a fixed 20cm distance at the side of and from the center of OLEV with variable heights of 50cm~150cm.
2010.09.27 View 11488