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Band gap engineering for single-layer graphene by using slow Li<sup>+</sup> ions
Ryu, Mintae,Lee, Paengro,Kim, Jingul,Park, Heemin,Chung, Jinwook IOP 2016 Nanotechnology Vol.27 No.31
<P>In order to utilize the superb electronic properties of graphene in future electronic nano-devices, a dependable means of controlling the transport properties of its Dirac electrons has to be devised by forming a tunable band gap. We report on the ion-induced modification of the electronic properties of single-layer graphene (SLG) grown on a SiC(0001) substrate by doping low-energy (5 eV) Li<SUP>+</SUP> ions. We find the opening of a sizable and tunable band gap up to 0.85 eV, which depends on the Li<SUP>+</SUP> ion dose as well as the following thermal treatment, and is the largest band gap in the <I>π</I>-band of SLG by any means reported so far. Our Li 1s core-level data together with the valence band suggest that Li<SUP>+</SUP> ions do not intercalate below the topmost graphene layer, but cause a significant charge asymmetry between the carbon sublattices of SLG to drive the opening of the band gap. We thus provide a route to producing a tunable graphene band gap by doping Li<SUP>+</SUP> ions, which may play a pivotal role in the utilization of graphene in future graphene-based electronic nano-devices.</P>
Ryu, Mintae,Lee, Paengro,Kim, Jingul,Park, Heemin,Chung, Jinwook IOP 2016 Nanotechnology Vol.27 No.48
<P>Bilayer graphene (BLG) has an extensive list of industrial applications in graphene-based nanodevices such as energy storage devices, flexible displays, and thermoelectric devices. By doping slow Na<SUP>+</SUP> ions on Li-intercalated BLG, we find significantly improved thermal and electronic properties of BLG by using angle-resolved photoemission and high-resolution core level spectroscopy (HRCLS) with synchrotron photons. Our HRCLS data reveal that the adsorbed Na<SUP>+</SUP> ions on a BLG produced by Li-intercalation through single layer graphene (SLG) spontaneously intercalate below the BLG, and substitute Li atoms to form Na-Si bonds at the SiC interface while preserving the same phase of BLG. This is in sharp contrast with no intercalation of Na<SUP>+</SUP> ions on SLG though neutral Na atoms intercalate. The Na<SUP>+</SUP>-induced BLG is found to be stable upon heating up to <I>T</I>?=?400 °C, but returns to SLG when heated at <I>T</I> <SUB>d</SUB>?=?500 °C. The evolution of the <I>π</I>-bands upon doping the Na<SUP>+</SUP> ions followed by thermal annealing shows that the carrier concentration of the <I>π</I>-band may be artificially controlled without damaging the Dirac nature of the <I>π</I>-electrons. The doubled desorption temperature from that (<I>T</I> <SUB>d</SUB>?=?250 °C) of the Na-intercalated SLG together with the electronic stability of the Na<SUP>+</SUP>-intercalated BLG may find more practical and effective applications in advancing graphene-based thermoelectric devices and anode materials for rechargeable batteries.</P>
김민태(Mintae Kim),오성업(Sungup Oh),성세진(Sejin Seong),백동기(Tongki Paek) 전력전자학회 1998 전력전자학술대회 논문집 Vol.- No.-
Many Harmonics components is contained within the stator currents of the High-speed Reluctance Synchronous Motor with salient pole rotor. They cause the power factor of RSM to get worse. In this paper, the mathematical model of RSM is investigated. And SV_PWM control method is applied to reduce Harmonics components in the stator currents. Simulation results shows the fast response of speed and the reduction of Harmonics components at steady state.<br/> <br/>