2D Materials – Preparation, Properties & Applications: Modeling & Simulations II
Sponsored by: TMS Functional Materials Division, TMS: Thin Films and Interfaces Committee
Program Organizers: Nuggehalli Ravindra, New Jersey Institute of Technology; Ramana Chintalapalle, University of Texas at El Paso; Gerald Ferblantier, University of Strasbourg - IUT LP / ICube Laboratory - CNRS; Sufian Abedrabbo, Khalifa University; Amber Shrivastava, Indian Institute of Technology Bombay
Thursday 8:30 AM
March 18, 2021
Room: RM 11
Location: TMS2021 Virtual
Session Chair: Gerald Ferblantier, University of Strasbourg; Amber Shrivastava, Indian Institute of Technology
8:30 AM
Cesium Lead Bromides - Structural, Electronic & Optical Properties: Aneer Lamichhane1; Nuggehalli Ravindra1; 1New Jersey Institute of Technology
In recent years, it has been found that lowering the dimensionality of halide perovskites has enhanced photoluminescence and stability than its three-dimensional counterpart. Further, the change in the dimensionality of an inorganic halide perovskite can evoke surprising ramifications to its intrinsic behavior. The dimensionality in perovskites is governed from its octahedral cages. In zero-dimension perovskites, the octahedral cages are discrete whereas they are connected with one another forming a layer in two dimension perovskites. Likewise, in three-dimension perovskites, the octahedral cages share the corner atoms with each other. This presentation describes the two-dimensional counterpart of cesium lead bromide perovskites. It presents electronic properties, optical properties and thermoelectric transport properties in conjunction with its three-dimensional structure. The emergence of new physical phenomena with respect to the decreasing dimensionality of cesium lead bromide perovskites are analyzed.
8:50 AM
Thermoelectric Properties of 2-D B4C Nanosheets: Adway Gupta1; Arunima Singh1; 1Arizona State University
B4C is an excellent high temperature thermoelectric material with a melting temperature of 2763 oC, Seebeck coefficient in the range of 100-300 μV/K and an extremely high hardness. In order to examine it’s stability, properties and thus application in the 2-D form, we employ van der Waals corrected density-functional theory to compute the formation energies of non-polar 2-D slabs of B4C cleaved along multiple directions. We find that the formation energies of the various slabs are similar, indicating lack of significant preference for a cleavage direction. For instance, B4C cleaved along (001), (012) and (101) planes have formation energies of 0.056 eV/atom, 0.105 eV/atom and 0.116 eV/atom, respectively, which are all below the threshold of 0.2 eV/atom where free-standing 2-D sheets are expected to be thermodynamically stable. We finally compute the thermoelectric coefficients of the 2-D slabs and preliminary results indicate that they perform as well as the bulk B4C.
9:10 AM
Low Temperature Phonon Anharmonicity in Tungsten Diselenide: Qingan Cai1; 1University of California, Riverside
Tungsten diselenide has been extensively studied for its potential applications in optoelectronic and valleytronic devices. Reliable and stable performance of these devices requires outstanding thermal properties of tungsten diselenide. In this work, temperature dependent phonon dispersions of bulk tungsten diselenide are measured by inelastic X-ray scattering along high symmetry directions in Brillouin zone. Ab initio phonon calculation based on Density Function Theory agrees well with the experimental results. The analysis about Grüneisen parameters of out-of-plane acoustic phonons (flexural mode) near 𝛤 indicates giant phonon anharmonicity. Our results provide the experimental measurement of phonon dispersions and revels the inhomogeneous interlayer interactions in tungsten diselenide. They are crucial in investigating the thermal conductivity of this popular material.
9:30 AM
Mechanism of Strain Transfer in Transition Metal Dichalcogenides for Phase Change Transistors: Shoieb Ahmed Chowdhury1; Tara Peńa1; Stephen Wu1; Hesam Askari1; 1University of Rochester
Transition metal dichalcogenides (TMD) based transistors are attracting interest due to the superior performance in offer by eliminating static and dynamic power consumption problems associated with conventional switching mechanism. Recently, it has been shown that the transformation between semiconducting and metallic/semi-metallic phases using nanoscale strain engineering results in such switching behavior at device scale. Since strain is the driving factor in controlling electrical properties in these materials, we use a combination of modelling and experimental approaches to examine and quantify the mechanism of strain transfer in multilayer TMDs. Using molecular dynamics (MD) models with spectroscopy such as RAMAN the length scale of strain transfer is explored for several TMDs including MoS2, MoSe2, MoTe2 along with the effects of chalcogen and transition metal atoms. Results from the atomistic model coupled with observations from Raman spectroscopy reveals the mechanism of strain transfer at device scale and its efficiency in various experimental setups.