Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session P16: 2D Devices: Black Phosphorous, III-IV, and IV-VI MaterialsFocus
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Sponsoring Units: DMP Chair: Jewook Park, ORNL Room: 315 |
Wednesday, March 16, 2016 2:30PM - 2:42PM |
P16.00001: Twisted Phosphorene Nanoribbons Woosun Jang, Kisung Kang, Aloysius Soon Many different forms of structural deformations have been employed to alter the electronic structure of various two-dimensional (2D) nanomaterials in various optoelectronic devices [1]. Given the recent interest in the new class of 2D nanomaterials -- phosphorene, it is important to understand how the anisotropic strain-dependent electronic properties of low-dimensional phosphorene may be exploited for technological gain. Here, using first-principles density-functional theory, we investigate the mechanical stability of twisted one-dimensional phosphorene nanoribbons (PNR) by measuring its critical twist angle ($\theta_{\rm c}$) and shear modulus as a function of the applied mechanical torque [2-4]. We find a strong anisotropic behaviour in PNRs with different edge terminations and directions, and report the direct consequence of this applied mechanical stress on its corresponding electronic (and optical) properties. [1] E. S. Reich, \textit{Nature}, \textbf{506}, 19 (2014); [2] C. D. Reddy \textit{et al., Appl. Phys. Lett.} \textbf{94}, 101904 (2009); [3] E. M. Diniz, \textit{Appl. Phys. Lett.} \textbf{104}, 083119 (2014); [4] V. Sorkin and Y. Zhang, \textit{Nanotechnology}, \textbf{26}, 235707 (2015) [Preview Abstract] |
Wednesday, March 16, 2016 2:42PM - 2:54PM |
P16.00002: Ground state degeneracy, energy barriers, and molecular dynamics evidence for two-dimensional disorder in black phosphorus and monochalcogenide monolayers at finite temperature Mehrshad Mehboudi, Salvador Barraza-Lopez, Alex M. Dorio, Wenjuan Zhu, Arend van der Zande, Hugh O. H. Churchill, Alejandro A. Pacheco-Sanjuan, Edmund O. Harriss, Pradeep Kumar Mono-layers of black phosphorus and other two dimensional materials such as mono-layers of SiSe, GeS, GeSe, GeTe, Sns, SnSe, and SnTe with a similar crystalline structure have a four-fold degenerate ground state that leads to two-dimensional disorder at finite temperature. Disorder happens when neighboring atoms gently re-accommodate bonds beyond a critical temperature. In this talk, the effect of atomic numbers on the transition temperature will be discussed. In addition Car-Parinello molecular dynamics calculations at temperatures 30, 300 and 1000 K were performed on supercells containing more than five hundred atoms and the results from these calculations confirm the transition onto a two-dimensional disordered structure past the critical temperature, which is close to room temperature for many of these compounds. References: M. Mehboudi, A.M. Dorio, W. Zhu, A. van der Zande, H.O.H. Churchill, A.A. Pacheco Sanjuan, E.O.H. Harris, P. Kumar, and S. Barraza-Lopez. arXiv:1510.09153. [Preview Abstract] |
Wednesday, March 16, 2016 2:54PM - 3:06PM |
P16.00003: Remarkably low-energy one-dimensional fault line defects in single-layered phosphorene Aloysius Soon, Woosun Jang, Kisung Kang Systematic engineering of atomic-scale low-dimensional defects in two-dimensional nanomaterials is a promising way to modulate the electronic properties of these nanomaterials. Defects at interfaces such as grain boundaries and line defects can often be detrimental to technologically important nanodevice operations and thus a fundamental understanding of how such one-dimensional defects may have an influence on its physio-chemical properties is pivotal to optimizing their device performance. In this study [1], using density-functional theory, we investigate the temperature-dependent energetics and electronic structure of a single-layered phosphorene with various fault line defects. We have generated different line defect models based on a fault method, rather than the conventional rotation method. This has allowed us to study and identify new low-energy line defects, and we show how these low-energy line defects could well modulate the electronic band gap energies of single-layered two-dimensional phosphorene -- offering a range of metallic to semiconducting properties in these newly proposed low-energy line defects in phosphorene. [1] A. Soon et al. {\it Nanoscale}, DOI 10.1039/C5NR05605E (2015) [Preview Abstract] |
Wednesday, March 16, 2016 3:06PM - 3:18PM |
P16.00004: Black phosphorus edges: a polarized Raman study H Ribeiro, C Villegas, D Bahamon, A Castro Neto, E de Souza, A Rocha, M Pimenta, C de Matos Black phosphorus (BP) has been recently exfoliated down to few-layer thicknesses revealing numerous interesting features such as a tunable direct bandgap. Ever since, demonstrations of BP electronic devices have bloomed, as well as studies of the electric, optical, mechanical and thermal properties of its bulk and few-layer forms. However, the edges of BP crystals have, so far, been poorly characterized, even though the terminations of layered crystals are known to possess a range of interesting properties. In this work, the edges of exfoliated BP flakes are characterized by polarized confocal Raman spectroscopy. We will present experimental Raman spectra at zigzag and armchair edges, as well as density functional theory calculations that explain the peculiarities of the experimental data. [Preview Abstract] |
Wednesday, March 16, 2016 3:18PM - 3:30PM |
P16.00005: Tight-binding model study of topological properties in few-layer black phosphorus Hyeonjin Doh, Hyoung Joon Choi We study the simplest tight-binding model describing the band structures of mono- and bilayer phosphorus. The band structures are analyzed for various tight-binding parameters, and the gap-closing conditions are found where the system turns into a Dirac semi-metal. We show the tight-binding model Hamiltonian can be reduced to Dirac Hamiltonian and investigate its topological properties. The doping, electric field and pressure effects on topological properties of black phosphorus are discussed and these analyses suggest directions the the control of the energy gap in these system. [Preview Abstract] |
Wednesday, March 16, 2016 3:30PM - 3:42PM |
P16.00006: N-type doping of black phosphorus by using benzyl viologen. Dewu Yue, Daeyeong Lee, Jungjin Ryu, Min Sup Choi, Hye Jin Nam, Duk-Young Jung, Won Jong Yoo Black phosphorus (BP) meets several critical material requirements for the development of future nanoelectronic applications, but the realization of n-type semiconductor behavior form it has remained elusive. Here, we report the ambipolar characteristics of few-layer BP, induced using an novel technique: chemical doping with benzyl viologen (BV), which serves as a surface charge transfer donor for BP flakes. The n-doped BP devices exhibit excellent electron mobility up to \textasciitilde 83 cm$^{\mathrm{2}}$V$^{\mathrm{-1}}$s$^{\mathrm{-1}}$ from 2-terminal measurement at 300K, thereby demonstrating n-type behavior. On the basis of ambipolar BP devices, we also comprehensively analyzes temperature and BP thickness dependence of ambipolar devices, in which we found the degenerate doping limit below around 150K and highest electron transport performance in \textasciitilde 10 nm BP flakes at 300K. As a proof of concept, ultrafast BP photodetectors were fabricated with a very high photoresponsivity of \textasciitilde 10$^{\mathrm{4}}$ mA/W over the UV, visible, and IR spectral ranges. Furthermore, we fabricated a homogeneous BP based inverter through BV doping and h-BN capping that offers a feasible approach to fabricating a key building block of future 2D logic semiconductors. [Preview Abstract] |
Wednesday, March 16, 2016 3:42PM - 3:54PM |
P16.00007: Oxidation of black phosphorus from the side Mario Borunda, Salvador Barraza Two-dimensional black phosphorus, a recently discovered two-dimensional semiconductor material, has promising properties of interest in physics and materials science. We have performed density functional theory calculations at the early stages of the oxidation process from its side, and contrasted these results with oxidation processes happening at the top exposed surface. [Preview Abstract] |
Wednesday, March 16, 2016 3:54PM - 4:06PM |
P16.00008: Intrinsic Defects, Fluctuations of the Local Shape, and the Photo-Oxidation of Black Phosphorus Kainen Utt, Salvador Barraza-Lopez, Alejandro Pacheco SanJuan, Pablo Rivero, Mershad Mehboudi, Edmund Harriss, Mario Borunda The rapid degradation of black phosphorus (BP) under ambient condition is a well-known, but poorly understood phenomenon that represents a significant challenge to the feasibility of BP-based devices. Nearly 60 years after its discovery, BP has experienced a resurgence in popularity among the condensed matter community due to its recently demonstrated promise as a tunable two-dimensional semi-conductor. Despite this resurgence in popularity, the oxidation pathways have yet to be explored in great detail. A full characterization of the material's shape and of its electronic properties at the early stages of the oxidation process is presented and provides fundamental insights into the degradation dynamics of this novel layered material. Reference: K. L. Utt, P. Rivero, M. Mehboudi, E. O. Harriss, M. F. Borunda, A. A. Pacheco SanJuan, and S. Barraza-Lopez, ACS Cent. Sci. 1, 320 (2015) [Preview Abstract] |
Wednesday, March 16, 2016 4:06PM - 4:18PM |
P16.00009: Humidity Effects and Anisotropic Etching During Exfoliated Black Phosphorus Degradation Alexandre Favron, Patricia Moraille, Etienne Gaufres, Tycho Roorda, Pierre L. Levesque, Richard Leonelli, Richard Martel Black phosphorus, a lamellar structure similar to graphene, is a high mobility semiconductor having a tunable optical band gap from 0.3 eV up to \textasciitilde 2 eV with decreasing layer thickness. Our previous study has highlighted a fast photo-oxidation in ambient conditions when black phosphorus is exfoliated as thin layers. The kinetics of this degradation is also enhanced by quantum confinement effects and faster for the thinnest layers, which represents an important hurdle to prepare few layers. Here we further investigate the role of water in the process by following the reaction kinetics in different humidity using fast AFM imaging. We report on important changes of wettability of thin layers at room temperature depending on the degradation stages and layer thickness. For a given level of humidity at equilibrium, we observe the formation of water droplets. Those droplets form preferentially on defects sites and cracks and then grow on the thicker parts of the flake to finally accumulate on to the thinnest regions. This sequence of water droplet growth faster from thick to thin layers is interpreted as being due to a lowering of surface tension with decreasing layer thickness. In a second study, the oxidation kinetics of layers completely immersed in water reveal an anisotropic oxidation process with preferential etching in specific orientations of the crystal. This study will be discussed in the context of a reactivity of black phosphorus that appears both anisotropic and thickness-dependent. [Preview Abstract] |
Wednesday, March 16, 2016 4:18PM - 4:30PM |
P16.00010: First-principle study of the energy barrier and diffusivity of a Li atom on phosphorene Congyan Zhang, Ming Yu The energy landscape of a Li atom adsorbed on the phosphorene was studied using the first principle method. Four types of preferential adsorption positions were found: three of them are located along the zigzag direction with the adsorption energy of -2.0\textasciitilde -1.9 eV/atom, forming potential valleys along zigzag direction. The other type is located on the top of the puckered bridge with the adsorption energy of -1.4 eV/atom, forming small isolated shallow basins between the potential valleys. Based on this energy landscape, we calculated energy barriers along various diffusion paths. The lowest energy barrier is along the zigzag direction in the valley (0.09 eV). The highest energy barrier is along the armchair direction through the top of P atoms (1.01 eV). While the energy barrier on the top of the bridge along the zigzag direction and along the armchair direction through the P-P bonds are 0.20 eV and 0.79 eV, respectively. Estimated diffusivity along the zigzag direction in the valley is almost 10$^{\mathrm{16}}$ fast than that along the armchair direction through the top of P atoms, indicating the anisotropic diffusion. [Preview Abstract] |
Wednesday, March 16, 2016 4:30PM - 4:42PM |
P16.00011: Large Ultraviolet Photoresponsivity of Few-layer Black Phosphorus JING WU, Gavin Kok Wai Koon, Du Xiang, Antonio H. Castro Neto, Barbaros O¨zyilmaz Black phosphorus has recently gained much attention in the scientific community. Black phosphorus can be seen as a crystal generated by periodic repetition of tetraphosphorus (P$_{4})$ molecules. It is known that tetraphosphorus P$_{4}$ can be transformed temporarily to diphosphorus P$_{2}$ upon ultraviolet (UV) irradiation. Thus, it is expected that the P$_{4}$ structured black phosphorus also has strong interaction with light especially in the UV range. Here we report on the optoelectronic characteristics of few-layer black phosphorus field effect transistors (FETs) ranging from the UV to the near infrared (NIR). We demonstrate that black phosphorus is an excellent ultraviolet (UV) photodetector with a specific detectivity \textasciitilde 3x10$^{13}$ Jones. We report also an exceptional photo responsivity of 10$^{7}$ times higher than previously reported values for black phosphorus visible light photodetectors. We attribute such a colossal UV photo responsivity to the resonant-interband transition between two specially nested valence and conduction bands. These nested bands provide an unusually high density of states for high-efficient UV absorption due to their singularity nature. [Preview Abstract] |
Wednesday, March 16, 2016 4:42PM - 4:54PM |
P16.00012: \textbf{Few-layer III-VI and IV-VI 2D semiconductor transistors} Sukrit Sucharitakul, Mei Liu, Rajesh Kumar, Raman Sankar, Fang C. Chou, Yit-Tsong Chen, Xuan Gao Since the discovery of atomically thin graphene, a large variety of exfoliable 2D materials have been thoroughly explored for their exotic transport behavior and promises in technological breakthroughs. While most attention on 2D materials beyond graphene is focused on transition metal-dichalcogenides, relatively less attention is paid to layered III-VI and IV-VI semiconductors such as InSe, SnSe etc which bear stronger potential as 2D materials with high electron mobility or thermoelectric figure of merit. We will discuss our recent work on few-layer InSe 2D field effect transistors which exhibit carrier mobility approaching 1000 cm$^{\mathrm{2}}$/Vs and ON-OFF ratio exceeding 10$^{\mathrm{7}}$ at room temperature. In addition, the fabrication and device performance of transistors made of mechanically exfoliated multilayer IV-VI semiconductor SnSe and SnSe$_{\mathrm{2}}$ will be discussed. \textbf{References} [1] Sucharitakul. S. \textit{et al. Nano Lett}. \textbf{15,} 3815--3819 (2015).~ [Preview Abstract] |
Wednesday, March 16, 2016 4:54PM - 5:06PM |
P16.00013: Puckering Inversion in Monolayer Group IV Monochalcogenides SnS and GeSe Through Strain Engineering Paul Hanakata, Alexandra Carvalho, David Campbell, Harold Park .We use first principles calculations to study the electronic and mechanical properties of the monolayer group IV monochalcogenides SnS and GeSe under uniaxial stress in the armchair or zigzag direction.~ We find that monolayer SnS and GeSe can sustain tensile stresses up to 3.5 GPa and 7 GPa, respectively. Applying uniaxial stress in the zigzag direction results in a structural phase transition to a rocksalt-like structure for both GeSe and SnS and followed by an inversion in the puckering structure.~ This puckering inversion results in a change of the band structure, in particular the valley configuration. Our findings show the potential applications of SnS and GeSe monolayer for phase-change memory and valley-based electronic devices. [Preview Abstract] |
Wednesday, March 16, 2016 5:06PM - 5:18PM |
P16.00014: ABSTRACT WITHDRAWN |
Wednesday, March 16, 2016 5:18PM - 5:30PM |
P16.00015: Field Effect Transistors Using Atomically Thin Layers of Copper Indium Selenide (CuInSe) Prasanna Patil, Sujoy Ghosh, Milinda Wasala, Sidong Lei, Robert Vajtai, Pulickel Ajayan, Saikat Talapatra We will report fabrication of field-effect transistors (FETs) using few-layers of Copper Indium Selenide (CuInSe) flakes exfoliated from crystals grown using chemical vapor transport technique. Our transport measurements indicate n-type FET with electron mobility \textmu $\approx $ 3 cm$^{\mathrm{2}}$ V$^{\mathrm{-1}}$ s$^{\mathrm{-1}}$ at room temperature when Silicon dioxide (SiO$_{\mathrm{2}})$ is used as a back gate. Mobility can be further increased significantly when ionic liquid 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF$_{\mathrm{6}})$ is used as top gate. Similarly subthreshold swing can be further improved from 103 V/dec to 0.55 V/dec by using ionic liquid as a top gate. We also found ON/OFF ratio of $\approx $ 10$^{\mathrm{2}}$ for both top and back gate. Comparison between ionic liquid top gate and SiO$_{\mathrm{2}}$ back gate will be presented and discussed. [Preview Abstract] |
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