The Spring Semester Seminar
■ Topic : A New Material Design based on electrides encompassing 2-dimensional electron gas (2DEG)
■ Speaker : Prof. SungWng Kim (Dept. Energy Science, Sungkyunkwan Univ.)
■ Date : Mar 24 (Tue) 16:00
■ Venue : KAIST Applied Engineering Bd. (W1), Multimedia Lecture Room (1st Floor)
■ Abstract : Solvated electrons in alkali metal-ammonia solution have been a diverse stem for scientific and applied researches. The alkali metal-ammonia solution containing solvated electrons can be condensed into ionic solid, known as electrides. Electride, which is regarded as a new electronic material, is ionic crystal in which interstitial electrons serve as anions. The physical properties of electrides are determined by the topology of cavities or channels which confine anionic electrons. The confining sites have been restricted to cavities or weakly linked channels of organic systems.
In this talk, several inorganic electrides with different confining structures will be introduced as a new electro-active functional material in physics, electronics, chemistry and thermoelectrics. First, the subnanometer-sized cage network structure electride, [Ca24Al28O64]4+(4e-) have showed a variety of electrical properties such as insulator-semiconductor, metal-insulator and metal-superconductor transition. This subnanometer-sized cage network structure shows a low workfunction of 2.4eV. Second, the layered structured electride, calcium nitride was synthesized and highlighted with transport properties exhibiting the two dimensionally (2D) confined electron gas. A 2D transport characteristic of the bulky material is evidenced by a high electron mobility exceeding 1000 cm2×V-1s-1. Third, we recently discovered a new electride system in carbides with layered structure. Surprisingly, their physical properties exhibited a ferromagneticity according to the degree of localization of interstitiale lectrons. The recent experimental and theoretical studies on ferromagnetic electrides will be discussed.