2015 International Workshop on Emerging Functional Electronic Materials and Devices

2015 International Workshop on Emerging Functional Electronic Materials and Devices

WELCOME TO EEMD 2015

EEMD2015 is jointly organized by the annual “International Workshop on Emerging Electronic Materials and Devices” and the annual “International Workshop on Nanomaterials and Nanodevices”. EEMD2015 aims at scholarly exchange of information on recent progresses in functional materials and their applications to emerging devices, and at fostering research collaborations.
The week-long EEMD2015 Workshop has two parts: a 3-day conference and a 4-day hands-on training. The conference is from June 30 to July 2, with internationally renowned speakers presenting latest and exciting work. The topics of the conference cover experiment, theory and modeling. The second part of EEMD2015 is a 4-day hands-on training session, July 3 to July 6. The goal of the hands-on session is to help young researchers and students to improve basic research skills by using most advanced modeling techniques and softwares in density functional theory (DFT) for materials modeling and nonequilibrium Green’s function (NEGF) based DFT for quantum transport modeling. The hands-on session will also briefly cover theoretical backgrounds of both DFT and NEGF-DFT, and discuss interesting directions for solving emerging problems in materials and devices.

Wish you a wonderful trip in Beijing!

COMMITTEES

Conference Chairpersons

Hongjun Gao vice director of the IOP and the UCAS, China

Hong Guo McGill University, Canada

Scientific advisory committee

Sokrates T. Pantelides Vanderbilt University, USA

Min Ouyang Maryland University, USA

Werner Hofer Newcastle University, UK

Shouheng Sun Brown University, USA

Organizing and Program committee

Wengang Lu IOP, CAS

Yeliang Wang IOP, CAS

Hongjun Xiao IOP, CAS

Haiming Guo IOP, CAS

Yalan Feng IOP, CAS

Wei Ji Renmin University

Scientific Program

Abstract

Advances in Raman Spectroscopy of Graphene

and Layered Materials

Andrea C. Ferrari

Cambridge Graphene Centre, University of Cambridge, Cambridge, CB3 OFA, UK

Raman spectroscopy is an integral part of graphene research [1]. It is used to

determine the number and orientation of layers, the quality and types of edges, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups[2,3]. I will review the state of the art, future directions and open questions in Raman spectroscopy of graphene and related materials, focussing on the effect of disorder[3,4], doping[5,6] and deep UV laser excitation[7]. I will then consider

the shear [8] and layer breathing modes(LBMs)[9], due to relative motions of the plane, either perpendicular or parallel to their normal. These modes are present in all layered materials[10,11]. Their detection allows one to directly probe the interlayer interactios

[10,11]. They can also be used to determine the elastic constants associated with these displacements: the shear and out-of-plane elastic moduli[12]. This paves the way to the use of Raman spectroscopy to uncover the interface coupling of two-dimensional hybrids and heterostructures[10-12].

References:

1. A. C. Ferrari et al. Phys. Rev. Lett. 97, 187401 (2006)

2. A.C. Ferrari, D.M. Basko, Nature Nano. 8, 235 (2013)

3. A.C. Ferrari, J Robertson, Phys. Rev. B 61, 14095 (2000)

4. G. Cancado et al. Nano Lett. 11, 3190 (2011)

5. M. Bruna et al. ACS Nano 8, 7432 (2014)

6. A. Das et al. Nat. Nanotechnol. 3, 210 (2008)

7. A.C. Ferrari, S. Milana, P. H. Tan, D. M. Basko, P. Venezuela, submitted (2015)

8. P. H. Tan et al. Nature Materials 11, 294 (2012)

9. X. Zhang et al. Phys. Rev. B 87, 115413 (2013)

10. J. B. Wu et al. Nature Comms 5, 5309 (2014)

11. J.B. Wu et al. arXiv:1505.00095 (2015)

12. S. Milana et al. submitted (2015)

The Quantum Properties of Magnetic Atoms on Surfaces

Andreas Joachim Heinrich

Almaden Research Center, IBM, USA

The scanning tunneling microscope is an amazing experimental tool because of its atomic-scale spatial resolution. This can be combined with the use of low temperatures, culminating in precise atom manipulation and spectroscopy with microvolt energy resolution. In this talk I will apply these techniques to the investigation of the quantum spin properties of transition metal atoms on surfaces. I will highlight the interesting similarities and differences of those systems with the corresponding gas-phase atoms.

Transition Metal Dichalcogenides: Growth, Characterization and Modification

Ludwig Bartels

University of California at Riverside

I will present the growth of transition metal dichalcogenides films (MoS2, MoSe2, WS2, WSe2, MoTe2) and their alloys via chemical vapor deposition and high vacuum techniques.4 Local optical spectroscopy in conjunction with photoelectron spectroscopy shed light on the materials’ native electronic properties and their variation in the presence of contacts.1, 2 Post-growth processing allows chalcogen exchange towards local change of bandgap.3 Deposition onto functional substrates such as ferroelectrics permits further local modification of the material properties toward device applications.5

References:

1V. Klee, E. Preciado, D. Barroso, A. E. Nguyen, C. Lee, K. J. Erickson, M. Triplett, B. Davis, I. H. Lu, S. Bobek, J. McKinley, J. P. Martinez, J. Mann, A. A. Talin, L. Bartels, and F. Leonard, 'Superlinear Composition-Dependent Photocurrent in Cvd-Grown Monolayer Mos2(1-X)Se2x Alloy Devices', Nano Letters, 15 (2015), 2612-19.

2D. Le, A. Barinov, E. Preciado, M. Isarraraz, I. Tanabe, T. Komesu, C. Troha, L. Bartels, T. S. Rahman, and P. A. Dowben, 'Spin-Orbit Coupling in the Band Structure of Monolayer Wse2', J Phys Condens Matter, 27 (2015), 182201.

3Q. ma, M. Isarraraz, C wang, E. Preciado, V. Klee, S. Bobek, K. Yamaguchi, E. li, P. M. Odenthal, A. nguyen, D. Barroso, D. Sun, G. V. Palacio, M. Gomez, A. nguyen, D. Le, G Pawin, J. mann, T. F. Heinz, T. Rahman, and L Bartels, 'Postgrowth Tuning of the Bandgap of Single-Layer Molybdenum Disulfide Films by Sulfur/Selenium Exchange', Acs Nano, 8 (2014), 4672-77.

4J. Mann, Q. Ma, P. M. Odenthal, M. Isarraraz, D. Le, E. Preciado, D. Barroso, K. Yamaguchi, G. V. Palacio, A. Nguyen, T. Tran, M. Wurch, A. Nguyen, V. Klee, S. Bobek, D. Z. Sun, T. F. Heinz, T. S. Rahman, R. Kawakami, and L. Bartels, '2-Dimensional Transition Metal Dichalcogenides with Tunable Direct Band Gaps: Mos2(1-X)Se2x Monolayers', Advanced Materials, 26 (2014), 1399-404.

5A. Nguyen, P. Sharma, T. Scott, E. Preciado, V. Klee, D. Sun, I. H. Lu, D. Barroso, S. Kim, V. Y. Shur, A. R. Akhmatkhanov, A. Gruverman, L. Bartels, and P. A. Dowben, 'Toward Ferroelectric Control of Monolayer Mos2', Nano Lett, 15 (2015), DOI: 10.1021/acs.nanolett.5b00687.

Transport through 1-dimension Nanostructures

Wenjie Liang, Wengang Lv, Yuchun Zhang, Xiao Guo, Liyan Zhou, Shangqian Zhao

Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190, China

Ballistic transport and quantum confinements in low dimensional materials play important roles determining many interesting transport behaviors. In this talk we will discuss our progress in studying 1-dimension transport through single double-layered carbon nanotubes and gold nanowires. The interplay between the layered-structure of the former and ballistic transport of electrons in gold will be shown in details.

Spin Torque Effect in Spin-Filter Based Magnetic Tunnel Junction

Yu-Hui Tang(唐毓慧)1 , Fa-Chieh Chu(朱法杰)1 , and Nicholas Kioussis2

1 Department of Physics, National Central University, Jhong-Li, Taiwan

2 Department of Physics, California State University, Northridge, CA, USA

Recent discoveries in the ferromagnet/insulator/ferromagnet (FM/I/FM) magnetic tunnel junctions (MTJs) have demonstrated that the relative orientation of the two FM electrodes can be either altered by an external magnetic field, i.e. the tunneling magnetoresistance (TMR) effect, or controlled by a spin-polarized current, i.e. the current-induced magnetization reversal via the spin transfer torque (STT) effect. The spin-transfer, , and field-like, , components of the STT originate from different components of the spin current accumulated at the FM/I interface and can be expressed in terms of the interplay of spin current densities and of the non-equilibrium interlayer exchange couplings [1], respectively, solely in collinear configurations.

The insulator in conventional FM/I/FM MTJs plays only a passive role in the spin-polarized transport. The evolution beyond passive components has broadened the quest for multifunctional spintronic devices consisting of spin-filter (SF) barriers [2], which exploits the separation of the barrier heights of the two spin channels that can be in turn tuned via an external magnetic field.

In this study [5], the tight binding calculations and the non-equilibrium Green's function formalism is employed to study the effect of the SF-barrier magnetization on the bias behavior of both components of STT in noncollinear FM/I/SF/I/FM junctions. We predict a giant in contrast to conventional FM/I/FM junctions, which has linear bias dependence, is independent of the SF thickness, and has sign reversal via magnetic field switching. Our results suggest that the novel dual manipulation of either by a magnetic field or bias can be employed for “reading” or “writing” processes, respectively, in the next-generation field-like-spin-torque MRAM (FLST-MRAMs). Finally, our newly derived general expressions of noncollinear and allows the efficient calculation of the STT from collinear ab initio electronic structure calculations [3,4]. (Contract No. NSC 102-2112-M-008-004-MY3)

References:

1. Y. –H. Tang et al., Phys. Rev. B 81, 054437 (2010).
2. T. S. Santos and J. S. Moodera, Phys. Today 63, 46 (2010).
3. X. Jia, K. Xia, Y. Ke, and H. Guo, Phys. Rev. B 84, 014401 (2011).
4. Y. –H. Tang and F. –C. Chu, J. Appl. Phys. 117, 093901 (2015).
5. Y. –H. Tang, F. –C. Chu, and N. Kioussis, Sci. Rep. 5, 11341 (2015).

Things Strange and Wonderful at the Nanoscale

Sokrates T. Pantelides

Department of Physics and Astronomy

and Department of Electrical Engineering and Computer Science

Vanderbilt University, Nashville, TN 37235 USA

and Materials Science and Technology Division

Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA

The combination of density functional theory calculations and aberration-corrected scanning transmission electron microscopy is a powerful way to probe nanostructures with atomic resolution. In this talk I will describe a few recent examples: a) the discovery of a new form of crystalline order that we termed “interlaced crystals”, namely ABX2 tetrahedrally-bonded structures in which the two cations that share a sublattice can exist in a large number of ordered arrangements, giving rise to interlaced domains, while the underlying Bravais remains intact [1]; b) fabrication and characterization of ultrathin (three atoms across) nanowires out of a molybdenum dichalcogenide monolayers [2], and c) the demonstration of low-loss electron-energy-loss spectroscopy as a powerful complement to optical spectroscopies, but with spatial resolution [3].

References:

[1] X. Shen, E. A. Hernandez-Pagan, W. Zhou, Y. S. Puzyrev, J. C. Idrobo, J. E. Macdonald, S. J. Pennycook, and S. T. Pantelides, “Interlaced crystals having a perfect Bravais lattice and complex chemical order revealed by real space crystallography”, Nature Comm. 5, 5431 (2014).

[2] J. Lin, O. Cretu, W. Zhou, K. Suenaga, D. Prasai, K. I. Bolotin, N. T. Cuong, M. Otani, S. Okada, A. R. Lupini, J.-C. Idrobo, D. Caudel, A. Burger, N. J. Ghimire, J. Yan, D. G. Mandrus, S. J. Pennycook, and S. T. Pantelides, “Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers”, Nature Nanotech. 9, 436-442 (2014).

[3] M. D. Kapetanakis, W. Zhou, M. P. Oxley, J. Lee, M. P. Prange, S. J. Pennycook, and S. T. Pantelides, "Atomically resolved maps of valence electron excitations with application to graphene", submitted for publication.

Supramolecular Materials for Future Devices: Investigating Structure, Electron and Spin States

N. Ballav1, M. Stöhr2,7, J. Lobo-Checa2,8, P. M. Oppeneer3, L. H. Gade,4 S. Decurtins, F. Diederich, C. Thilgen, A. Kleibert1, T. A. Jung1

1 Department of Synchrotron Radiation, Paul Scherrer Institute, Switzerland
2 Department of Physics, University of Basel, Switzerland
3Dept. of Physics and Astronomy, Uppsala University, Sweden

4University of Heidelberg, Germany

5Departments of Chemistry ETH Zürich, Switzerland,

6University of Bern, Switzerland

7Zernike Institute for Advanced Materials, University of Groningen, Netherlands

8Centro de Física de Materiales (CSIC-UPV/EHU),San Sebastián, Spain

E-mail:

Well defined electronic and spintronic interfaces can be architectured by combining self-assembly and surface science. The atomically clean metal surface in the ultra-high vacuum provides a very specific environment affecting the behaviour of the ad-molecules as well as the adsorbent-adsorbate interaction. Depending on the bonding at the interface, complex electronic and magnetic interactions can occur which can be explored by spectro-microscopy correlation, in this case photoemission and X-ray photoabsorption spectroscopy (PES, XAS) and scanning tunnelling microscopy (STM).

The emergence of quantum dot states from the interaction of a porous network with the 2D (Shockley) surface state of Cu(111) exhibits sufficient residual coupling to show the onset of a band-like structure in angle resolved photoemission [1]. Selected surface-supported molecules have been shown to exhibit ferromagnetic [2] or anti-ferromagnetic [3] exchange interaction, and their spin systems have been shown to be tunable by physical parameters and / or chemical stimuli [4]. Supramolecular chemistry can be combined with on-surface coordination chemistry to reversibly switch the spin of self-assembled bi-molecular arrays [5].

All these examples have in common that the substrate-molecular interfaces are well defined by their production from atomically clean substrates and molecular building blocks. The physics and chemistry of these unprecedented systems, which are addressable by scanning probes, provide insight into novel materials in their assembly, their electronic and spintronic properties which emerge from the interaction of their components down to the scale of single atoms, molecules and bonds.

References:

[1] J. Lobo-Checa et al. Science 325, 300 (2009)

[2] A. Scheybal et al. Chem. Phys. Lett. 411, 214 (2005)

[3] D. Chylarecka et al. J. Phys. Chem. Lett. 1, 1408–1413 (2010)

[4] C. Wäckerlin et al. Nature Communications 2010, 1:61 DOI: 10.1038/ncomms1057

[5] C. Wäckerlin et al. Advanced Materials 25, 2404-2408 (2013)

[6] For a complete list of contributing authors refer to the individual publications

Synthesis and Assembly of Nanoparticle Catalysts for Efficient Electrochemical Reduction Reactions

Shouheng Sun

Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA

Recent advance in nano-fabrication has made it possible to design and synthesize nanoparticles with nearly precise controls of nanoparticle size, shape, composition and structure for catalytic applications. In this talk, I will summarize the common methods we used to synthesize monodisperse nanoparticles, especially intermetallic nanoparticles, core/shell nanoparticles, nanowires and their self-assemblies on graphene (or N-doped graphene) surface. I will use Au-, Pt-, and Cu-based elemental and alloy nanoparticles as examples to demonstrate the rational tuning and enhancement of nanoparticle catalysis for selective electrochemical reduction of proton, oxygen, and carbon dioxide for renewable energy applications.

Growth of Small Organic Molecules on A Variety of

Graphene Substrates

Christian Teichert

Institute of Physics, Montanuniversität Leoben, Franz Josef Str. 18, 8700 Leoben, Austria

* ;

Crystalline films of small semiconducting organic molecules offer attractive potential for optoelectronic applications on flexible substrates. However, these applications require a transparent and flexible electrode material; and here the novel material graphene (Gr) comes into play. Since small conjugated molecules like the rod-like molecule para-hexaphenyl (6P) fit well to the hexagonal structure of graphene, growth of 6P on Gr can be expected in a lying configuration.

As observed in situ by low-energy electron microscopy, 6P grows at 240 K indeed in a layer-by-layer mode with lying molecular orientation on Ir(111) supported graphene [1]. 6P islands nucleate at Gr wrinkles [2]. At higher temperatures, needle-like 6P crystallites - also composed of lying molecules - are found [3]. On exfoliated, wrinkle-free graphene, such needles develop with discrete orientations defined by the Gr lattice as detected by atomic-force microscopy [4]. Interestingly, for few-layer exfoliated Gr the needle length decreases significantly with increasing layer number [5].