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Positive magnetoconductance and dephasing in strongly localized black phosphorus
Lee, Tae‐,Ho,Hwang, Euyheon,Choi, Jung‐,Bum,Bae, Myung‐,Ho WILEY‐VCH Verlag Berlin GmbH 2016 Physica Status Solidi. Rapid Research Letters Vol.10 No.11
<P>We study the magnetoconductance and dephasing in a strongly localized regime in black phosphorus (BP) devices. The phase coherence length, <I>l</I><SUB><I>φ</I></SUB> obtained from the magnetoconductance follows a temperature dependence of <I>T</I><SUP>–1/3</SUP> in the strongly localized regime with <I>k</I><SUB>F</SUB><I>l</I><SUB>e</SUB> < 1 (<I>ξ</I> < <I>l</I><SUB><I>φ</I></SUB>) based on the Ioffe–Regel criterion. Here <I>k</I><SUB>F</SUB>, <I>l</I><SUB>e</SUB> and <I>ξ</I> are the Fermi wave vector, mean free path and localization length, respectively. The conductance behavior as a function of temperature confirms that the transport regime of our BP is in a variable‐range‐hopping regime, which results in the strongly localized regime.</P>
Brzhezinskaya, Maria,Irzhak, Artemii,Irzhak, Dmitry,Kang, Tae Won,Kononenko, Oleg,Matveev, Viktor,Panin, Gennady,Roshchupkin, Dmitry WILEY‐VCH Verlag Berlin GmbH 2016 Physica Status Solidi. Rapid Research Letters Vol.10 No.8
<P>For the first time, a few layer graphene was grown on the surface of the polar <I>X</I> ‐cut (110) of a piezoelectric La<SUB>3</SUB>Ga<SUB>5.5</SUB>Ta<SUB>0.5</SUB>O<SUB>14</SUB> crystal by the CVD method. This polar <I>X</I> ‐cut is characterized by a good matching of the crystal lattice parameters of La<SUB>3</SUB>Ga<SUB>5.5</SUB>Ta<SUB>0.5</SUB>O<SUB>14</SUB> and two‐dimensional graphene crystal, as well as the presence of piezoelectric fields on the surface of the substrate, which could affect the graphene growth process. Raman spectroscopy investigation has shown the ability for direct growth of graphene on the piezoelectric crystal. The NEXAFS spectroscopy studies of the film grown on the surface of the <I>X</I> ‐cut of an La<SUB>3</SUB>Ga5<SUB>.5</SUB>Ta<SUB>0.5</SUB>O<SUB>14</SUB> crystal also confirmed that the grown film is graphene. Moreover, the NEXAFS spectra enable the conclusion that additional electron states are formed as a result of chemical bonding between the atoms of graphene and the substrate which proceeds through hybridization of the valence electron states of the substrate and graphene atoms. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)</P>
Electro‐optic switching with liquid crystal graphene
Kim, Min Jae,Park, Ji Hyun,Yamamoto, Jun,Kim, Youn Sang,Scalia, Giusy WILEY‐VCH Verlag Berlin GmbH 2016 Physica Status Solidi. Rapid Research Letters Vol.10 No.5
<P>Graphene oxide (GO) particles in aqueous dispersions can form liquid crystal (LC) phases at extremely low concentrations due to the extremely high aspect ratio of the flakes and noticeably, they possess an extremely large Kerr coefficient attractive for low power consumption electro‐optic devices. Reduced graphene does not easily form LC phases in water due to its hydrophobic nature but here we show that stable dispersions of reduced graphene oxide can be realized with surfactants and that they exhibit birefringence upon shearing as well as under application of electric fields. The performance of the system is largely superior to GO LC possessing longer time stability and drastically improved electro‐optic properties with an induced birefringence twice as large at the same field strength thanks to the almost recovery of graphene properties upon reduction. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)</P>
Hong, Seongin,Yoo, Geonwook,Kim, Dong Hak,Song, Won Geun,Le, Ong Kim,Hong, Young Ki,Takahashi, Kaito,Omkaram, Inturu,Son, Do Ngoc,Kim, Sunkook WILEY‐VCH Verlag Berlin GmbH 2017 Physica status solidi. PSS. C, Current topics in s Vol.14 No.3
<P>Seongin Hong et al. (article no. <url href='http://doi.wiley.com/10.1002/pssc.201600262'>1600262</url>) have investigated the polyethylenimine (PEI) doping mechanism and its effect on the electrical and optical properties of multilayer MoS<SUB>2</SUB> field effect transistors (FETs). Density functional theory (DFT) calculation and X‐ray photoelectron spectroscopy (XPS) measurement confirm that the PEI molecules were successfully doped and formed Mo–N bonds on the MoS<SUB>2</SUB> channel, generating new energy states near the valence band. The strong n‐doping changed the threshold voltage as well as the Schottky barrier width attributed to the induced interfacial dipoles. Therefore, the ON‐current of the doped MoS<SUB>2</SUB> FETs was improved in comparison with the pristine FETs. Furthermore, the PEI doping also enhanced the photoresponsivity of the MoS<SUB>2</SUB> FETs from 0.14 A/W to 4.41 A/W. This study suggests that PEI molecular doping could be widely applicable to two‐dimensional materials in order to improve the electrical and optical properties of respective devices.</P>