Entropy of Exciton Formation in 2D Atomic Layer Transition Metal Dichalcogenides

POSTER

Abstract

The 2-dimensional atomic layer transition metal dichalcogenides (TMDCs, MX$_{\mathrm{2}}$; M$=$Mo or W; X$=$S, Se, or Te) are of special importance for optoelectronic applications because of the structural tunability of bandgaps in visible and near-infrared regions and the bandgap crossover from direct (monolayer) to indirect (bilayer or multilayer). The role of the acoustic phonon energy and electron-phonon coupling which is critical to the formation of excitons is investigated using the O'Donnell and Chen relation for temperature-dependent bandgaps of semiconductors. The change in entropy of exciton formation is given by the derivative of the O'Donnell and Chen relation when the bandgap energy is the standard Gibbs free energy. The analysis suggests the change in entropy of exciton formation with higher energy phonons (100 meV) is constant until 90 K while lower energy phonons (10 meV) approaches a constant value of $-2Sk_{B} $ between 250 K and 300 K where$S$is the strength of electron-phonon interaction and $k_{B} $is the Boltzmann constant. Increased scattering and spontaneous decay probabilities of higher energy phonons may result from the larger electron-phonon interaction of less energetic phonons. A \textasciitilde 3-fold increase in the change in entropy of exciton formation was observed while the electron-phonon coupling strength largely determines the bandgap energy compared to the average acoustic phonon energy. Acknowledgement: This work at HU is supported by ARO W911NF-15-1-0535, NSF HRD-1137747, and NASA NNX15AQ03A.

Authors

  • Quinton Rice

    Hampton University

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO

  • Jonathan Tan

    Duquesne University, Baker Hughes, Hampton University, Korea Research Institute of Standards and Science, Electronics and Telecommunications Research Institute, Texas Christian University, University of North Texas Health Science Center, Austin Peay State University, Virginia Military Institute, Pennsylvania State University, University of Virginia, Washington University, National Institute for Materials Science, Japan, Tokyo Metropolitan University, Japan, Univ of Kentucky, Argonne National Laboratory, Oak Ridge National Laboratory, Univ of Virginia, James Madison University, Department of Chemistry & Biochemistry, High Point University, Department of Chemistry, High Point University, Department of Physics, James Madison University, Department of Physics & Astronomy, Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond, VA, Institute of Renewable Energy and Environment Technology, University of Bolton, Bolton, UK, Division of Materials Science and Engineering, Ames Laboratory, US Dept. of Energy, Ames, IA, Lehigh University, University of Pardubice, Universite de Rennes, Jan Dlugosz University, Translume, NSCL/FRIB, Duke University, University of Massachusetts - Amherst, University of St. Andrews, National Radio Astronomy Observatory, University of Florida, Yale University, None, Georgia College & State Univ, Georgia College & State University, National University of Sciences and Technology (NUST), Univ of Tennessee Space Inst, The University of Virginia, Chiang Mai University, DHA Suffa University, Faculty of Chemical Technology, University of Pardubice, Pardubice, Czech Republic, Department of Physics and Astronomy, Austin Peay State University, Clarksville, TN, United States, George Mason University, Northern Virginia Community College, Department of Physics, University of Virginia, Istanbul University, Georgia College and State University, University of Houston, Western Kentucky Univ, James Madison University, Virginia Polytechnic Institute and State University, Pontifica Universidad Catolica de Chile, Trent University, Univ of Arizona, Ohio State University, NRAO, University of Virginia/NRAO

  • Felix Seo

    Hampton University