Center for Relativistic Laser Science

Writing is a habit!

Happy new year to all of you!

What a year we had in 2016! Once again, it has been another harsh year for me. Sun still rises and sets. A new year 2017 has come! That is our life.

Year 2016, we finished installation of two TEMs (ARM 200 keV and 300 keV). The 300 keV TEM is still under installation and will be finished early this year with new detectors. Thanks to prof. Young Min Kim and Sang Ho Oh for the installation effort. Without their efforts, this would have been impossible. Superuser system has been progressed but still needs to be improved. Thanks to Equipment Purchase and Maintenance Committee members, in particular prof. Seong Chu Lim for his devotion and all the superusers for their time and devotion.

Year 2017 means a lot to us. This is 5th fiscal year of our Center. At the end of this year, we will have to wrap up for the mid-term evaluation, although the real evaluation meeting will be held in 2018. In fact we improved a lot last year in terms of science quality and technological breakthroughs. From simple statistics, we published 99 papers and among them 47 papers were published in top-tier 5% journals with high impact factors of higher than 10, much improved compared to the previous year’s record. This simply implies that we all tried hard to improve our science. Thanks to all of you for this. We will continue our effort this year as well.

I am happy that we made some progresses in several research areas. To list some of them, we have successfully grown large area monolayer metallic 1T’-MoTe₂ and AB-stacked bilayer graphene via chemical vapor deposition. Furthermore, our unique approach of growing transition metal dichalcogenides was realized in general to many other TMD materials and their growth mechanism using liquid precursors and promotors was fully understood by the synthesis team. Many collaborative researches with 2D materials are in progress domestically and internationally. Continued from last year of thermoelectricity, we provided a new perspective of engieering thermoelectricity for the first time via atomic arrangement of point defects, dislocations, and grain boundaries. We also found that quantum phases such as superconductivity, magnetoresistance, and Weyl semimetal can be engineered in MoTe₂–based materials in conjunction with vacancy defects and alloys. I am also excited that we were able to demonstrate 2D materials indeed to reveal the best multiple exciton generation performance in terms of ideal threshold energy (2Eg) and carrier conversion efficiency (>98%), the best data among all existing materials. There were some progresses in mechanical properties of 2D materials that 2D dislocations and hyperdislocations are generated depending on exfoliation conditions and the dislocation emission propagates via formation of plastic zone at the crack tip of less than 5 nm, very different from either ductile material or brittle material. Progresses in 2D heterostructures have been impressive. By simply establishing hBN/Gr heterostructures, we were able to construct two-terminal memory devices that may emulate neuromorphic signaling and memory function. Extension of this device to demonstrate photodetector with high responsivity and detectivity, the world-best record in this research, is another technical breakthrough. The developed concept of exciton-plasmon polariton via Ag NW/2D hybrid last year was further continued to demonstrate for high speed optical communication unit, which demonstrated clearly the concept of exciton transistor with three key functions of wavelength multiplexing, electric-optical/optical-electrical modulator, and photodetector. Quantum-mechanical tunneling interpretation on photocurrent extraction in Gr/MoS₂/Gr is another breakthrough in ultrathin 2D devices. These are still ongoing researches. We hope to continue this tradition of breakthroughs.

During the course of discussion with many of you last year, I struggled a lot in writing paper as well as improving our science. I also noticed that some of you have a hard time in writing a paper. Not only in writing paper logically but also even to start writing paper! As a scientist, we have one premise, ‘publish or perish’ or ‘paper talks in science’, while money talks in economy. This is so obvious when you think just a few seconds. As a scientist, there are not many means to communicate with other scientists. Personal communication, paper, presentation.. What else? Among them, paper is the most universal, long-term effective, and record-keeping. Why do we have to communicate? Because this way the next follower will not repeat the same thing and knowledge accumulation continues via our science practice. This is how mankind has evolved so far. In practice, if you do not publish, you don’t get a good job. So simple answer without such sophisticated reasons. Papers are somehow a sort of reward to me and a prize to your hard work. You know the feeling when you finish writing paper. It does not matter whether the paper is great or not, the paper is published in good journal or not. Just happy feeling of achievement. The more suffering, the more joy and sometimes even tearing.

In spite of such obvious reasons, why are we lazy in writing? I think this is related to your previous habit. A habit of writing diary, a habit of writing lab notebook, a habit of writing letters, a habit of writing any kind of small memos for you... I see there is a strong correlation. Those who do not write lab notebook have a difficulty in start writing or writing logically. All your logical practices come from your daily practice of logic with your data obtained. You can always write your small logic in the lab notebook. Why do you start your experiment? What is your motivation? This is of course the novelty of your paper. When you decide to do experiment, why do you do it? Although you think, unless you do not write it down on your notebook, you do not really think. When you write it, you reconsider it again and find more logical questions sometimes. Your daily behavior of life and experimentation must have some reason. Don’t be lazy to ask questions to yourself, why? and how?

So my message in 2017, develop your good habit of writing! To your notebook! not to your ppt file or computer. I still believe the power of pen and pencil. Test yourself! Tell me if I am wrong.

Director of CINAP

Young Hee Lee