平成25年度 国際交流助成受領者による国際会議参加レポート

In the symposium, I presented my research on work function variation in alkali metal (Li, Na, K, Rb, and Cs) / W(110) surface. This study gives generalization of the electronic structure of the adsorbed alkali metals in relation to the variation in work function. The density of states profiles of the alkali metals at different coverage served as a possible indicator to determine the behavior of work function which gives a minimum value at an optimum coverage. Low work function materials are important for thermionic devices and also find application as plasma electrode for negative ion production.

Discussion with the participants:

1. Most of the participants are experimentalists and are therefore more interested with the application and findings of the work rather than the technical aspect and the methodology. Although the topic is quite old, making generalization of the behavior of the electronic structure for the different types of alkali metal and as a function of their coverage is the contribution of this work. Indeed, the participants who are working with low work function materials are glad to see theoretical investigation in this area of study.
2. Similar with the comments from our experimental collaborators from the National Institute of Fusion Science-Japan, I learned from the participants that the “stability” of low work function materials is among the major concern at present. The adsorbed alkali metals on metal surface reduce the work function of the system; however the alkali metal atoms are removed or ejected during the operation. This requires high maintenance and is not practical for a long term application. This issue coincides with the future plan of this study which is to design stable low work function material. Nonetheless, the basic knowledge obtained from the present status of the study will be used to engineer new material.
3. As I mentioned with the experimentalists that I plan to work on “implanted” alkali metal atoms in metal substrate in the future, they were delighted and commented with it as challenging. The challenge relies on maintaining both factors of stability and low work function characteristics. This further motivated me and as a researcher in the computational field to do intelligent design for the functionalization of materials - stable low work function material in particular.
4. Other interesting points of discussion that gave me insights to further improve my work are the following:
   a. Local electrostatic potential energy
   b. Possibility of using alkali metal oxide, e.g. cesium oxide
   c. Simple criteria to get low work function from adsorbed atom or molecule on a specific substrate

AVS60

The Symposium features all aspects of research that utilizes vacuum technology. International researchers from both the academes and industries attended the symposium. Different vacuum technology-related companies and scientific journal publishers highlighted the exhibit session.

1. The American Vacuum Society is interested to establish connection with other international vacuum societies. During the award ceremony night, the AVS recognized Vacuum Society of Japan (VSJ) and gave token to Prof. Hideaki Kasai (VSJ representative) and other vacuum societies. This effort of AVS is made me realize the importance of collaboration not only in research activities but also to scientific societies as well.
2. Some of the presentations that dealt with first principles investigations incorporated the computational data to support their experimental findings. I had the chance to ask some presenters that are dealing with alloy surfaces of the possible issues of surface segregation and effect of the alloys toward their concerned reactions. I also took the opportunity to share what I am doing and my point of view as a researcher in the computational field with regard to this matter. Although AVS main concern is on vacuum technology, the organizers provided session on computational design. Different approaches based from DFT, monte carlo, molecular dynamics and others were presented by the lecturers. The role of the session is to show the capabilities of computational works to elucidate and predict physical phenomena. This acknowledgment on the importance of computational work motivated me to at least incorporate in my research activities the factors such as prediction, elucidation and functionalization of materials.
3. Some of the topics that I attended which I shared with the members of our research group have the following theme: electrolyte for low temperature operating solid oxide fuel cells; electronic structures of graphene and silicene supported by metal substrates; importance of vacancies and defects in the catalytic performance of metal oxides; role of hydrogen atoms in the stabilization and growth of nanorods; effect of quantum tunneling for a more accurate experimental data; and atom segregation in alloy surfaces and clusters affecting catalytic activity of the material.

Personal impression and learning:

I am honored to be a part of the symposium. I learned a lot from the different experimental techniques provided by the presenters as I am mainly involved in the computational field. Also, I realized that it is essential to have collaboration or consultation between an experimentalist and theoretician to grasp clear understanding of a physical phenomenon happening in a particular system of concern. Also, the people I met gave me the opportunity to expand my network as a young researcher. The ideas I gained during the discussions provided me additional perspectives on how to deal with different problems which benefited me in the aspect of improving my research activities. With these, I am truly grateful to Marubun Research Promotion Foundation for the travel support granted to me. Young researchers like me truly appreciate the concern and dedication of the foundation to support students in attending scientific conferences for their own personal growth and for a better promotion of science.

平成25年度 国際交流助成受領者一覧に戻る