Young-il Song

Significant reduction of leakage current in the TiO2/Si structure by the insertion of the CeO2 intermediate layer

The insertion of the CeO2 intermediate layer between the TiO2 layer and the Si substrate reduced the leakage current significantly after rapid thermal annealing (RTA) in O2 ambient for 3 min. After RTA, the TiO2/CeO2/Si structure showed a significantly lower leakage current than the TiO2/Si structure. At a proper voltage of −2 V, which was defined as the difference between the applied gate bias and the flatband voltage, the leakage current density of the TiO2/CeO2/Si structure was ∼10−8 A/cm2, while the leakage current density of the TiO2/Si sample was ∼10−2 A/cm2. The formation of the intermixed structure of TiO2 and CeO2 at the TiO2/CeO2 interface by RTA was thought to contribute to the reduction of the leakage current.

Study of complex electrodeposited thin film with multi-layer graphene-coated metal nanoparticles

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Power Enhancement of Lithium-Ion Batteries by a Graphene Interfacial Layer.

We achieved a method for power enhancement of heavy-duty lithium-ion batteries (LIBs) by synthesizing a graphene interfacial layer onto the anode copper current collector (ACCC). We tested fabricated coin cells, which used either 35-μm-thick rolled pristine copper foil or graphene synthesized onto the pristine copper foil for power output estimation of the LIBs. We observed the copper surface morphology with a scanning electron microscope (SEM). Raman spectroscopy was used to measure the bonding characteristics and estimate the layers of graphene films. In addition, transmittance and electrical resistance were measured by ultra-violet visible near-infrared spectroscopy (UV-Vis IR) and 4 point probe surface resistance measurement. The graphene films on polyethylene terephthalate (PET) substrate obtained a transmittance of 97.5% and sheet resistance of 429 Ω/square. Power enhancement performances was evaluated using LIB coin cells. After 5C current discharge rate of -1.7 A/g reversible capacity of 293 mAh/g and 326 mAh/g were obtained for pristine and synthesized graphene anode current collectors, respectively. The graphene synthesized onto the ACCC showed superior power performance. The results presented herein demonstrate a power enhancement of LIBs by a decrease in electron flow resistivity between active materials and the ACCC and removal of the native oxide layer on the anode copper surface using high quality graphene synthesized onto the ACCC.