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Gapped Nearly Free-Standing Graphene on an SiC(0001) Substrate Induced by Manganese Atoms
황진웅,이지은,강민희,박병규,Jonathan Denlinger,모성관,황춘규 한국진공학회 2018 Applied Science and Convergence Technology Vol.27 No.5
The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angleresolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.
Controlling spin-orbit coupling strength of bulk transition metal dichalcogenide semiconductors
이영훈,Eu Pilsun,임창영,차재훈,김성헌,Denlinger Jonathan D.,김영관 한국물리학회 2021 Current Applied Physics Vol.30 No.-
Transition metal dichalcogenide (TMD) semiconductors are attracting much attention in research regarding device physics based on their unique properties that can be utilized in spintronics and valleytronics. Although current studies concentrate on the monolayer form due to the explicitly broken inversion symmetry and the direct band gap, bulk materials also hold the capability of carrying spin and valley current. In this study, we report the methodology to continuously control the spin-orbit coupling (SOC) strength of bulk TMDs Mo1-xWxSe2 by changing the atomic ratio between Mo and W. The results show the size of band splitting at the K valley the measure of the coupling strength is linearly proportional to the atomic ratio of Mo and W. Our results thus demonstrate how to precisely tune the SOC coupling strength, and the collected information of which can serve as a reference for future applications of bulk TMDs.
Temperature-Dependent Electron–Electron Interaction in Graphene on SrTiO<sub>3</sub>
Ryu, Hyejin,Hwang, Jinwoong,Wang, Debin,Disa, Ankit S.,Denlinger, Jonathan,Zhang, Yuegang,Mo, Sung-Kwan,Hwang, Choongyu,Lanzara, Alessandra American Chemical Society 2017 NANO LETTERS Vol.17 No.10
<P>The electron band structure of graphene on SrTiO3 substrate has been investigated as a function of temperature. The high-resolution angle-resolved photoemission study reveals that the spectral width at Fermi energy and the Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a BN substrate. Near the charge neutrality, the energy-momentum dispersion of graphene exhibits a strong deviation from the well-known linearity, which is magnified as temperature decreases. Such modification resembles the characteristics of enhanced electron electron interaction. Our results not only suggest that SrTiO3 can be a plausible candidate as a substrate material for applications in graphene-based electronics but also provide a possible route toward the realization of a new type of strongly correlated electron phases in the prototypical two-dimensional system via the manipulation of temperature and a proper choice of dielectric substrates.</P>
Gapped Nearly Free-Standing Graphene on an SiC(0001) Substrate Induced by Manganese Atoms
Hwang, Jinwoong,Lee, Ji-Eun,Kang, Minhee,Park, Byeong-Gyu,Denlinger, Jonathan,Mo, Sung-Kwan,Hwang, Choongyu The Korean Vacuum Society 2018 Applied Science and Convergence Technology Vol.27 No.5
The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.
황진웅,황춘규,정낙관,A. D. N’Diaye,A. K. Schmid,Jonathan Denlinger 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.4
The interface between graphene and a ferromagnetic substrate has attracted recent research interests due to its potential for spintronic applications. We report an angle-resolved photoemission spectroscopy study on the interface between graphene and cobalt epitaxially grown on a tungsten substrate. We find that the electron band structure of the interface exhibits clear discontinuities at the crossing points with cobalt 3d bands. These observations indicate strong hybridizations between the electronic states in the interface and provide an important clue to understand the intriguing electromagnetic properties of the graphene/ferromagnet interface.
Electronic-dimensionality reduction of bulk MoS<sub>2</sub> by hydrogen treatment
Cho, Soohyun,Kim, Beom Seo,Kim, Beomyoung,Kyung, Wonshik,Seo, Jeongjin,Park, Min,Jeon, Jun Woo,Tanaka, Kiyohisa,Denlinger, Jonathan D.,Kim, Changyoung,Odkhuu, Dorj,Kim, Byung Hoon,Park, Seung Ryong The Royal Society of Chemistry 2018 Physical chemistry chemical physics Vol.20 No.35
<P>A reduction in the electronic-dimensionality of materials is one method for achieving improvements in material properties. Here, a reduction in electronic-dimensionality is demonstrated using a simple hydrogen treatment technique. Quantum well states from hydrogen-treated bulk 2H-MoS2 are observed using angle resolved photoemission spectroscopy (ARPES). The electronic states are confined within a few MoS2 layers after the hydrogen treatment. A significant reduction in the band-gap can also be achieved after the hydrogen treatment, and both phenomena can be explained by the formation of sulfur vacancies generated by the chemical reaction between sulfur and hydrogen.</P>
Observation of tunable band gap and anisotropic Dirac semimetal state in black phosphorus
Kim, Jimin,Baik, Seung Su,Ryu, Sae Hee,Sohn, Yeongsup,Park, Soohyung,Park, Byeong-Gyu,Denlinger, Jonathan,Yi, Yeonjin,Choi, Hyoung Joon,Kim, Keun Su American Association for the Advancement of Scienc 2015 Science Vol.349 No.6249
<P><B>Tuning the band gap of black phosphorus</B></P><P>Most materials used in electronics are semiconductors. The sizable energy gap in their electronic structure makes it easy to turn the conduction of electricity on and off. Graphene naturally lacks this band gap unless it undergoes certain modifications. Kim <I>et al.</I> studied the electronic structure of black phosphorus—a related two-dimensional material. By sprinkling potassium atoms on top of single layers of black phosphorus, the material changed from being a semiconductor to having a gapless linear dispersion similar to that of graphene.</P><P><I>Science</I>, this issue p. 723</P><P>Black phosphorus consists of stacked layers of phosphorene, a two-dimensional semiconductor with promising device characteristics. We report the realization of a widely tunable band gap in few-layer black phosphorus doped with potassium using an in situ surface doping technique. Through band structure measurements and calculations, we demonstrate that a vertical electric field from dopants modulates the band gap, owing to the giant Stark effect, and tunes the material from a moderate-gap semiconductor to a band-inverted semimetal. At the critical field of this band inversion, the material becomes a Dirac semimetal with anisotropic dispersion, linear in armchair and quadratic in zigzag directions. The tunable band structure of black phosphorus may allow great flexibility in design and optimization of electronic and optoelectronic devices.</P>