Nanomaterials/Spectroscopy/Device Physics

Dimensionality is one of the most fundamental parameters that determine the physical characteristics of materials. This is not so obvious in ordinary macroscopic objects that consist of atoms bonded in a three-dimensional (3D) structure. However, the effect of dimensionality is more than conspicuous in crystalline solids that are arranged in 0D, 1D, or 2D structure. In fact, we observe dramatically different properties for a given chemical compound depending on how we arrange its crystal structure.

Our research group is interested in studying the electronic, optical, and chemical phenomena in atomically thin 2D crystals such as graphene and transition metal dichalcogenides. We aim to address technological challenges in the areas of optoelectronics, energy harvesting, and catalysis by exploiting the unconventional properties of these materials. Specifically, we focus on the following aspects of 2D crystals:

Light-matter interaction Exciton dynamics Charge transport Intercalation chemistry Phase transformation Colloidal processing Thin film growth Emerging photoluminescence from an atomically thin sheet of tungsten disulphide (WS2)

L. Chu, H. Schmidt, J. Pu, S. Wang, B. Özyilmaz, T. Takenobu, and G. Eda "Charge transport in ion-gated mono-, bi-, and trilayer MoS2 field effect transistors" Sci. Rep. 4, 7293 (2014). K.K. Amara, L. Chu, R. Kumar, M.Toh and G. Eda “Wet chemical thinning of molybdenum disulfide down to its monolayer” APL Mat. 2, 092509 (2014) D. Kozawa, R. S. Kumar, A. Carvalho,
A. K. Kumar, W. Zhao, S. Wang, M. Toh, R. M. Ribeiro, A. H. Castro Neto, K. Matsuda, G. Eda “Photocarrier relaxation pathway in two-dimensional semiconducting transition metal dichalcogenides” Nat. Comm. 5, 4543 (2014). J. Y. Tan, A. Avsar, J. Balakrishnan, G. K. W. Koon, T. Taychatanapat, E. C. T. O'Farrell, K. Watanabe, T. Taniguchi, G. Eda, A. H. Castro Neto and B. Özyilmaz “Electronic transport in graphene-based heterostructures” Appl. Phys. Lett. 104, 183504 (2014). A. V. Kretinin, Y. Cao, J. S. Tu, G. L. Yu, R. Jalil, K. S. Novoselov, S. J. Haigh, A. Gholinia, A. Mishchenko, M. Lozada, T. Georgiou, C. R. Woods, F. Withers, P. Blake, G. Eda, A. Wirsig, C. Hucho, K. Watanabe, T. Taniguchi, A. K. Geim, and R. V. Gorbachev “Electronic Properties of Graphene Encapsulated with Different Two-Dimensional Atomic Crystals” Nano Lett. 14, 3270 (2014). J. Wu, H. Schmidt, K.K. Amara, X. Xu, G. Eda, B. Özyilmaz “Large Thermoelectricity via Variable Range Hopping in CVD Grown Single-layer MoS2” Nano Lett. 14, 2730 (2014). H. Schmidt, S. Wang, L. Chu, M. Toh, R. Kumar, W. Zhao, A. H. Castro Neto, J. Martin, S. Adam, B. Özyilmaz, and G. Eda, “Transport Properties of Monolayer MoS2 Grown by Chemical Vapor Deposition” Nano Lett. 14, 1909 (2014). L.L.C. Wong, S. Barg, A. Menner, P.D. Pereira, G. Eda, M. Chowalla, E. Saiz, A. Bismarck, “Macroporous polymer nanocomposites synthesised from high internal phase emulsion templates stabilised by reduced graphene oxide” Polymer 55 395 (2014). D. Voiry, M. Salehi, R. Silva, T. Fujita, M.W. Chen, T. Asefa, V.B. Shenoy, G. Eda and M. Chhowalla “Conducting MoS2 Nanosheets as Catalysts for Hydrogen Evolution Reaction” Nano Lett. 13, 6222 (2013). W. Zhao, R.M. Ribeiro, M.L. Toh, A. Carvalho, C. Kloc , A.H. Castro Neto, and G. Eda “Origin of Indirect Optical Transitions in Few-Layer MoS2, WS2, and WSe2” Nano Lett. 13, 5627 (2013). W. Zhao, Z. Ghorannevis, K.K. Amara, J.R. Pang, M.L. Toh, X. Zhang, C. Kloc, P.-H. Tan, and G. Eda “Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2” Nanoscale 5, 9677 (2013) G. Eda and S. Maier “Two-Dimensional Crystals: Managing Light for Optoelectronics” ACS Nano 7, 5660 (2013). D. Voiry, H. Yamaguchi, J. Li, R. Silva, D.C.B. Alves, T. Fujita, M.W. Chen, T. Asefa, V.B. Shenoy, G. Eda, and M. Chhowalla “Enhanced catalytic activity in strained chemically exfoliated WS2 nanosheets for hydrogen evolution” Nat. Mater. (2013) doi:10.1038/nmat3700 L. King, W. Zhao, M. Chhowalla, J. Riley, and G. Eda “Photoelectrochemical properties of chemically exfoliated MoS2” J. Mater. Chem. A, 2013 G. Eda, A. Nathan, P. Wöbkenberg, F. Colleaux, K. Ghaffarzadeh, T.D. Anthopoulos, and M. Chhowalla “Graphene oxide gate dielectric for graphene-based monolithic field effect transistors” Appl. Phys. Lett. 102, 133108 (2013). M. Chhowalla, H.S. Shin, G. Eda, L.-J. Li, K. P. Loh and H. Zhang “The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets” Nature Chem. 5, 263 (2013). C. Petridis, Y.-H. Lin, K. Savva, G. Eda, E. Kymakis, T. D. Anthopoulos, and E. Stratakis “Post-fabrication, in situ laser reduction of graphene oxide devices” Appl. Phys. Lett. 102, 093115 (2013). Y. Huang, J. Wu, X. Xu, Y. Ho, G. Ni, Q. Zou, G. K. W. Koon, W. Zhao, A. H. Castro Neto, G. Eda, C. Shen, B. Özyilmaz “An innovative way of etching MoS2: Characterization and mechanistic investigation” Nano Res. 6, 200 (2013). W. Zhao, Z. Ghorannevis, L. Chu, M.L. Toh, C. Kloc, P.-H. Tan, and G. Eda “Evolution of electronic structure in atomically thin sheets of WS2 and WSe2” ACS nano 7, 791 (2013). G. Eda, T. Fujita, H. Yamaguchi, D. Voiry, M. Chen and M. Chhowalla “Coherent atomic and electronic heterostructures of single layer MoS2” ACS nano 6, 7311 (2012).