气体分子吸附调控CdG电子结构和磁性的第一性原理研究
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摘要
采用基于密度泛函理论的第一性原理方法,深入研究单个气体分子CO、NO、NO_2、SO_2、O_2和H2S吸附对Cd掺杂石墨烯(CdG)电子结构和磁性的影响及调控机理。结果表明:六种气体分子以较大的吸附能与CdG基底中的Cd原子键合并形成Cd-X键(X代表C,O,N,S),属于化学吸附;由气体吸附注入的空穴使得复合体系的电子分布发生重构,致使复合体系电子结构和磁性明显改变。CO吸附后,体系仍保持CdG基底原有的半导体性,但带隙宽度有所变化; NO、NO_2、SO_2和O_2吸附的CdG基底转变为金属性,H2S@CdG为半金属性。CO的吸附使得原本自旋极化的CdG基底磁性消失; NO_2、H2S、NO和O_2吸附基底时,产生局域自旋极化。对于NO_2@CdG和H2S@CdG,自旋极化主要分布于基底之上且极化方向相同,NO_2和H2S发生弱极化且自旋方向相反;而NO@CdG和O_2@CdG的自旋分布特征与之相反; SO_2@CdG呈现完全自旋极化特征,即SO_2和基底皆有显著的自旋分布但自旋方向不同。据此,由各气体分子引起体系电子结构和磁性的不同变化特征,可有效检测和甄别气体分子。
The effect of single gas molecule( CO,NO,NO_2,SO_2,O_2 and H_2S) adsorption on the electronic structures and magnetic properties of Cd-doped graphene( CdG) and its modulation mechanism were studied by using first-principles analysis based on density functional theory( DFT). The results show that gas molecule combines to the Cd atom in CdG substrate and Cd-X bond is formed( X = C,O,N,S),which belongs to chemisorption. The electron distribution of the combined system is reconstructed by the holes injected by gas adsorption,and the structures and magnetic properties of the combined system obviously change. For CO adsorption,the system remains the original semiconducting property of the CdG substrate,but the width of band gap is changed. The CdG substrate transforms into metallic property by adsorption of NO,NO_2,SO_2 and O_2,while H2 S @ CdG shows half-metallic property. In addition,the magnetism of the original spin-polarized CdG substrate disappears after CO adsorption; the systems of NO_2,H2 S,NO and O_2 adsorbed CdG produce the local spin-polarization; For NO_2@ CdG and H2 S@ CdG,spin-polarization are mainly distributed on the substrate and the two gas molecules have only weak polarization with opposite spin direction; In contrast,the spin distribution of NO@ CdG and O_2@ CdG is opposite. SO_2@ CdG shows the characteristics of complete spin polarization and the spin states of both the gas and CdG are in the opposite direction. Thus, gas molecule can be effectively detected and identified according to the different characteristics of electromagnetic properties caused by each gas molecule adsorption.
The effect of single gas molecule( CO,NO,NO_2,SO_2,O_2 and H_2S) adsorption on the electronic structures and magnetic properties of Cd-doped graphene( CdG) and its modulation mechanism were studied by using first-principles analysis based on density functional theory( DFT). The results show that gas molecule combines to the Cd atom in CdG substrate and Cd-X bond is formed( X = C,O,N,S),which belongs to chemisorption. The electron distribution of the combined system is reconstructed by the holes injected by gas adsorption,and the structures and magnetic properties of the combined system obviously change. For CO adsorption,the system remains the original semiconducting property of the CdG substrate,but the width of band gap is changed. The CdG substrate transforms into metallic property by adsorption of NO,NO_2,SO_2 and O_2,while H2 S @ CdG shows half-metallic property. In addition,the magnetism of the original spin-polarized CdG substrate disappears after CO adsorption; the systems of NO_2,H2 S,NO and O_2 adsorbed CdG produce the local spin-polarization; For NO_2@ CdG and H2 S@ CdG,spin-polarization are mainly distributed on the substrate and the two gas molecules have only weak polarization with opposite spin direction; In contrast,the spin distribution of NO@ CdG and O_2@ CdG is opposite. SO_2@ CdG shows the characteristics of complete spin polarization and the spin states of both the gas and CdG are in the opposite direction. Thus, gas molecule can be effectively detected and identified according to the different characteristics of electromagnetic properties caused by each gas molecule adsorption.
引文
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[2] Morozov S V,Novoselov K S,Katsnelson M I,et al. Giant Intrinsic Carrier Mobilities in Graphene and Its Bilayer[J]. Physical Review Letters,2008,100(1):016602.
[3] Novoselov K S,Geim A K,Morozov S V,et al. Electric Field Effect in Atomically Thin Carbon Films[J]. Science,2004,306(5696):666.
[4] Zhang Y B,Tan Y W,Stormer H L,et al. Experimental Observation of Quantum Hall Effect and Berry's Phase in Graphene[J]. Nature,2005,438(7065):201.
[5] Bolotin K I,Sikes K J,Jiang Z,et al. Ultrahigh Electron Mobility in Suspended Graphene[J]. Solid State Communications,2008,146(9):351-355.
[6] Lee C,Wei X D,Kysar J W,et al. Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene[J]. Science,2008,321(5887):385.
[7] Pham V H,Cuong T V,Hur S H,et al. Fast and Simple Fabrication of a Large Transparent Chemically-converted Graphene Film by Spraycoating[J]. Carbon,2010,48(7):1945-1951.
[8] Schwierz F. Graphene Transistors[J]. Nature Nanotechnology,2010,5:487-496.
[9] Xin Y C,Liu J G,Zhou Y,et al. Preparation and Characterization of Pt Supported on Graphene with Enhanced Electrocatalytic Activity in Fuel Cell[J]. Journal of Power Sources,2011,196(3):1012-1018.
[10] Schedin F,Geim A K,Morozov S V,et al. Detection of Individual Gas Molecules by Graphene Sensors[J]. Nature Materials,2006,6(9):652.
[11] Neto A H C. Selected Topics in Graphene Physics[J]. Lecture Notes in Physics,2010,244(11):4106-4111.
[12] Wehling T O,Novoselov K S,Morozov S V,et al. Molecular Doping of Graphene[J]. Nano Letters,2007,8(1):173-177.
[13] Zhao M,Yang F,Xue Y,et al. A Time-dependent DFT Study of the Absorption and Fluorescence Properties of Graphene Quantum Dots[J].Mol. Model.,2014,20(4):2214.
[14] Dai J,Yuan J,Giannozzi P. Gas Adsorption on Graphene Doped with B,N,Al,and S:a Theoretical Study[J]. Applied Physics Letters,2009,95(23):183.
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[16] Zhou M,Lu Y H,Cai Y Q,et al. Adsorption of Gas Molecules on Transition Metal Embedded Graphene:a Search for High-performance Graphene-based Catalysts and Gas Sensors[J]. Nanotechnology,2011,22(38):385502.
[17] Qi X J,Guo X,Zheng C G. Density Functional Study the Interaction of Oxygen Molecule with Defect Sites of Graphene[J]. Applied Surface Science,2012,259(259):195.
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[19] Qin X,Meng Q Y,Zhao W. Effects of Stone-wales Defect Upon Adsorption of Formaldehyde on Graphene Sheet with or Without Al Dopant:a First Principle Study[J]. Surface Science,2011,605(9):930-933.
[20] Dai J Y,Yuan J M. Modulating the Electronic and Magnetic Structures of P-doped Graphene by Molecule Doping[J]. Journal of Physics Condensed Matter,2010,22(22):225501.
[21] Kresse G,Hafner J. Ab Initio Molecular-dynamics Simulation of the Liquid-metal-amorphous-semiconductor Transition in Germanium[J].Physical Review B Condensed Matter,1994,49(20):13181-13185.
[22] Kresse G,Furthmüller J. Efficiency of Ab-initio Total Energy Calculations for Metals and Semiconductors Using a Plane-wave Basis Set[J].Computational Materials Science,1996,6:15-50.
[23] Kresse G,Furthmüller J. Efficient Iterative Schemes for Ab Initio Total-energy Calculations Using a Plane-wave Basis Set[J]. Phys Rev B Condens Matter,1996,54(16):11169-11186.
[24] Kresse G,Joubert D. From Ultrasoft Pseudopotentials to the Projector Augmented-wave Method[J]. Physical Review B,1999,59:1758-1775.
[25] Perdew J P,Burke S,Ernzerhof M. Generalized Gradient Approximation Made Simple[J]. Physical Review Letters,1996,77:3865.
[26] Janthon P,Vies F,Kozlov S M,et al. Theoretical Assessment of Graphene-metal Contacts[J]. J. Chem. Phys.,2013,138:244701.
[27] Grimme S. Semiempirical GGA-type Density Functional Constructed with a Long-range Dispersion Correction[J]. Journal of Computational Chemistry,2006,27:1787.
[28] Monkhorst H J,Pack J. Special Points for Brillouin-zone Integrations[J]. Physical Review B,1976,13:5188.
[29] Zhao Y X,Spain I L. X-ray Diffraction Data for Graphite to 20 GPa[J]. Physical Review B,1989,40(2):993-997.
[30] Neto A H C,Guinea F,Peres N M R,et al. Electronic Properties of Graphene Nanostructures[J]. Reviews of Modern Physics,2009,81:109.
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[35] Xu Y,Ruban A V,Mavrikakis M. Adsorption and Dissociation of O2on Pt-Co and Pt-Fe Alloys[J]. Journal of the American Chemical Society,2004,126:4717.