119th General Meeting of the KCS

Type Poster Presentation
Area 물리화학
Room No. 포스터발표장
Time 4월 20일 (목요일) 11:00~12:30
Code PHYS.P-23
Subject Colloidal Quantum Dots with Singly Occupied Higher Quantum State
Authors 정주연, 윤빛나, 정광섭*
고려대학교 화학과, Korea
Abstract Colloidal quantum dot (CQD) has been rigorously studied for the last three decades due to its tunable optical and electrical properties by varying the nanocrystal size. Since the CQD is semiconducting material, doping density can determine the CQD device performance. Therefore, it is very important to finely control the doping density of the CQD for manipulating the electric, optical and magnetic properties of CQDs. Previous work has shown the tunable intraband transition of mercury chalcogenide CQD by varying the nanocrystal size. Here, we firstly report HgSe CQDs with zero, one (unpaired) or two (paired) electrons occupying the lowest quantum state of the conduction band (1Se), which has been a long-standing challenge in the colloidal nanocrystal research. The number of electrons in the 1Se state is determined by nanocrystal growth time directly involved in the stoichiometry of the metal-chalcogenide CQD. The singly-occupied-quantum-state (SOQS), when an electron fills the 1Se state in stable under ambient conditions, was confirmed by carrying out the electron paramagnetic resonance spectroscopy. Furthermore, the diamagnetism was observed when zero or two electrons are occupied in the 1Se state, corresponding to doubly-occupied-quantum-state (DOQS). Strikingly, superparamagnetism was identified by performing SQUID for the SOQS HgSe CQDs with varying temperature down to 4 K. The number of electrons in the 1Se state, moreover, can be controlled by surface treatment. The SOQS and DOQS of CQD will be a promising magnetic feature for future spin based applications such as nonvolatile memory, infrared optoelectronics, catalysts, optomagneto-imaging and quantum computing.
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