Introduction of Research Activities at Emerging Device Physics Laboratory at Ewha
"Introduction of Research Activities at Emerging Device Physics Laboratory at Ewha"
- Understanding Memristive Behaviors in Metal Oxide Single Crystals and
- Semiconducting and Metal Nanostructures for Optoelectronic Device Applications
Drift and diffusion of oxygen vacancies have been believed to be main origin of memristive behavior, i.e., electricfield induced resistive switching (RS), of metal oxides. The concentration and spatial distribution of oxygen vacancies (mobile dopants) can change bulk resistivity and interface potential profiles, and also induce compositional variation, resulting in metallic phase formation and local Joule heating .
Single-crystalline metal-oxide-based rectifying junctions can exhibit RS during reversal of the applied voltage polarity, which can be model systems for investigating interfacial effects on RS characteristics. We have studied transport properties of the metal/SrTiO3 junctions and revealed local barrier height variations from Schottky diode model analyses and internal photoemission spectroscopy measurements . We also have carried out scanning probe microscopy (SPM) studies to examine local surface potential of the region under a large electric field in TiO2 single crystals and found that contact resistance and local work function of the TiO2 surface could be modified by the external bias voltage and ambient conditions .
All these results show that coupled electron-ion dynamics at the surface and interface of the metal oxides can play crucial roles in many interesting physical phenomena, including resistive switching. One-dimensional semiconductor nanowires (NWs) have attracted much attention for use in optoelectronic applications due to their unique optical and electrical properties. NWs are known to possess an vastly larger optical cross-section than geometrical cross-section, due to the guided mode and Fabry-Pérot resonances, as well as anti-reflection effects. As a vertical platform of an NW array, spectral dependence of the optical response can be further modified via controlling its period, filling ratio, and symmetric arrangement.
Metallic nanostructures have been used as plasmonic nanoantennas, allowing efficient conversion of propagating light into a nanoscale confined optical field. Our research interest has been focused on semiconductor nanostructure-based photodetectors/solar cells  and their performance enhancement strategies using plasmoic effects .
1. S. H. Chang et al., Phys. Rev. Lett. 102, 026801 (2009); S. H. Phark et al., Appl. Phys. Lett. 94, 022906 (2009); C. Park et al., Appl. Phys. Lett. 93, 042102 (2008); S. H. Chang et al., Appl. Phys. Lett. 92, 183507 (2008); S. C. Chae et al., Adv. Mater. 20, 1154 (2008).
2. E. M. Bourim et al., (submitted); E. Lee et al., Appl. Phys. Lett. 98, 132905 (2011); H. Kim et al., J. Phys. D: Appl. Phys. 42, 055306 (2009); C. Park et al., J. Appl. Phys. 103, 054106 (2008).
3. H. Kim et al., Appl. Phys. Lett. 100, 022901 (2012); H. Kim and D.-W. Kim, Appl. Phys. A. 102, 949 (2011); H. Kim et al., J. Phys. D: Appl. Phys. 43, 505305 (2010).
4. E. Lee et al., Sol. Energy Mater. Sol. Cells 103, 93 (2012); H.-D. Um et al., Appl. Phys. Lett. 98, 033102 (2011); B. O. Jung et al., Sens. Act. B 160, 740 (2011); H.-D. Um et al., IEDM (2010).
5. S.-W. Jee et al., (submitted); E. Lee et al., (submitted); M. Gwon et al., Opt. Exp. 19, 5895 (2011).