IBM Thomas J. Watson Research Center Bridging the Gap: Black Phosphorus for Electronics and Photonics Fengnian Xia Department of Electrical Engineering Yale University, New Haven CT 06511 Email: fengnian.ia@yale.edu Collaborators: UC: H. Wang; IBM: D. Farmer,. Han UW eattle: A. Jones, K. eyler, X. Xu WUTL: V. Tran, L. Yang; ARL: M. Chin, M. Dubey 1
Most popular 2D crystals: graphene, hbn, and TMDCs Graphene: E g =0 ev TMDCs (Transition Metal Dichalcogenides): Mo 2,W 2,Nbe 2 (MX 2 ) TMDCs: metals or semiconductors Boron Nitride: E g =6 ev ingle layer Mo 2 Is there a material which bridges the gap? Graphene: no bandgap; high mobility Boron Nitride: good dielectric TMDCs: Large gap > 1 ev; relatively low mobility; suitable for visible spectrum High Mobility (maybe not as high as that in graphene) A moderate bandgap: 0.5 to 1 ev uch a gap is also good for IR Han Wang, 04-13-2014 2 2
Black Phosphorus: A High Mobility Anisotrpic 2D Materials 1. Direct Bandgap: 0.3 ev 2. High Mobility: can be > 50,000 cm 2 /Vs in bulk at low T 3. Optical properties: large optical conductivity in 1 to 5 µm; great potential for infrared optoelectronics 4. trong in-plane Anisotropy: conceptually new devices in electronics and optoelectronics? Optical v.s. Electrical Bandgap z y 5.3 Å V. Tran et al. Phys. Rev. B 89, 235319 (2014). F. Xia, H. Wang, D. Xiao, M. Dubey, A. Ramasubramaniam, Nature Photonics, 8, 2014. (Invited Review Article) H. Wang, X. Wang, F. Xia, L. Wang, et al., Nano Letters, 14 (11), 2014. 3 Han Wang, 04-13-2014 3
Polarization-resolved Optical Conductivity and Angleresolved DC Conductivity ~ 30 nm Gap ~ 0.3 ev F. Xia, H. Wang, Y. Jia, Nature Communications, 5, 4458, 2014. H. Wang, X. Wang, et al., Nano Letters, 14 (11), 2014. X. Ling, H. Wang,. Huang, F. Xia, M. Dresselhaus, Proceedings of the National Academy of ciences (PNA), in press, 2015 (Invited Perspective Article) s q = s cos 2 (q -f)+s y sin 2 (q -f) s /s y ~ 1.5 Large and anisotropic optical conductivity in 1 to 5 µm wavelength: a promising material for near and mid-infrared optoelectronic. Han Wang, 04-13-2014 4 4
Angle-resolved Hall mobility z y m /m y ~1.8 High mobility: perfect for thin-film electronics; anisotropic mobility may allow for conceptually new electronic devices. F. Xia, H. Wang, Y. Jia, Nature Communications, 5, 4458, 2014. Research Highlight in Nature Photonics - Black Phosphorus Potential, 2014. Han Wang, 04-13-2014 5 5
Thin-film Black Phosphorus Field Effect Transistors along -direction D ~ 5 nm High mobility, high on-off ratio (>10 5 ), and good current saturation: ideal for thin-film RF electronics and Logic circuits F. Xia, H. Wang, Y. Jia, Nature Communications, 5, 4458, 2014. Research Highlight in Nature Photonics - Black Phosphorus Potential, 2014. Other groups: Prof. Yuanbo Zhang (Fudan), Prof. Peter Ye (Purdue), Prof. James Hwang (Lehigh), Prof. Barbaros Oezyilmaz (NU), Prof. Antonio Castro-Neto (NU), Dr. Andres Castellanos-Gomez etc. Han Wang, 04-13-2014 6 6
BP RF Transistors: Current Gain and Power Gain G Finite gap leads to current saturation and hence decent f ma BP BP D io 2 G D 50 mm H. Wang, X. Wang, F. Xia, L. Wang, M. Chin, M. Dubey,.-J. Han et al., Nano Letters, 14 (11), 2014. Han Wang, 04-13-2014 7 7
Highly anisotropic ecitons in monolayer black phosphorus y PL intensity in polar plot 6 µm armchair Ecitonic photoluminescence (PL) 1 nm Anisotropic wave function due to anisotropic mobility y Quasi-1D ecitons in a two-dimensional material In collaboration with University of Washington & Washington Univ. To appear in Nature Nanotechnology Han Wang, 04-13-2014 8 8
Anisotropic plasmons in monolayer black phosphorus (theory) Plasmonic Polarizer T. Low, R. Roldán, H. Wang, F. Xia, P. Avouris, L. M. Moreno, F. Guinea, Phys. Rev. Lett., 113, 106802, 2014. Han Wang, 04-13-2014 9 9
ummary Black Phosphorus: Bandgap: 0.3 ev; tunable (0.3-1.3 ev optical & 0.3-2 ev electrical) by layer number High Mobility: up to 600 cm 2 /Vs at room temperature measured in this work; can be > 50,000 cm 2 /Vs in bulk at low T Optical properties: large optical conductivity in 1 to 5 µm; attractive for infrared optoelectronics trong in-plane Anisotropy: conceptually new devices in electronics and optoelectronics. Bridging the gap: Potential applications in military, medicine and communications: High speed thin film electronics mid-ir to near-ir Optoelectronics, Polarization sensing, Plasmonic Polarizer IR light emitting devices: Infrared LEDs and Lasers. Han Wang, 04-13-2014 10 10
IBM Thomas J. Watson Research Center Acknowledgement tudents & Postdocs in Yale Collaborators in University of Washington, eattle, University of outhern California, MIT, Washington University in t Louis, Army Research Lab, Vienna Institute of Technology, and IBM Financial support: Yale University, ONR, AFOR, and NF 11