Showing papers by "Changhyun Ko published in 2009"

Dispersive capacitance and conductance across the phase transition boundary in metal-vanadium oxide-silicon devices

Abstract: Utilizing metal-vanadium oxide (VO2)-semiconductor capacitor device structures, we have investigated the temperature- and frequency-dependent dielectric and ac conductance responses of vanadium oxide thin films that undergo metal-insulator transition (MIT). In both metallic and insulating regimes, VO2-based devices showed large tunabilities as high as ∼95% and ∼42%–54%, respectively. The frequency dependence of capacitance and ac conductance displays power-law behavior with respect to temperature and applied voltage over a broad range. Low-frequency dispersion in dielectric properties was also observed and their onset frequency varies across the MIT from ∼0.5 MHz in insulating state to ∼50 kHz in metallic state. The results are of potential relevance to utilizing functional oxides in electronic devices.

Vanadium oxide thin films

Abstract: Thin films of vanadium oxide having exceptionally high metal-insulator transition properties are synthesized by RF sputtering. An Al2O3 substrate is placed in a sputtering chamber and heated to a temperature up to about 550 degrees Celsius. Ar and O2 gases are introduced into the sputtering chamber at the flow values of about 92.2 sccm and about 7.8 sccm respectively. A voltage is applied to create a plasma in the chamber. A sputtering gun with vanadium target material is ignited and kept at a power of about 250 W. The phase transition parameters of vanadium dioxide thin films, synthesized by RF sputtering, are modulated by exposing the vanadium dioxide thin film to UV (ultraviolet) radiation so as to induce a change in oxygen incorporation of the vanadium dioxide thin film.