Effect of vacancies on thermopower of molybdenum disulfide monolayers

Title

Effect of vacancies on thermopower of molybdenum disulfide monolayers

Creator

Patil S.B.; Sankeshwar N.S.; Mulimani B.G.

Description

A detailed theoretical investigation of the effect of scattering of electrons and phonons by lattice vacancies in molybdenum disulfide (MoS2) monolayers (MLs) on diffusion, S d, and phonon-drag, S g, components of thermoelectric power (TEP), S, is presented over a wide-temperature range (1 < T < 300 K) using the Boltzmann transport formalism. The diffusion component is assumed to be influenced, not only by vacancies via short-range and Coulomb disorder scattering, but also by charged impurities (CIs) and acoustic and optical phonons. In the case of S g, the phonons are considered to be scattered, besides the vacancies, by sample boundaries, substitutional isotopic impurities, as well as other phonons via both N- and U-processes. Numerical calculations of S d and S g, as functions of temperature and vacancy defect density are presented for MoS2 MLs with n s = 1017 m-2 supported on SiO2/Si substrates. The role of carrier scatterings by mono-sulfur and mono-molybdenum vacancies in influencing the overall electron and phonon relaxation rates and in determining S d and S g are investigated. The behavior of S d and S g is found to be noticeably influenced by vacancy scattering. The influence on S d is seen to be more for mono-sulfur vacancies for densities lesser than 1%. The influence, is to enhance S d slightly for MLs with realizable CI concentrations. On the other hand, S g is found to depend sensitively on the vacancy disorder for T < 50 K; a S-vacancy density of 0.1% is found to suppress the characteristic peak of S g by almost 60%. The extent of reduction in the characteristic peak of S g, observable in low temperature measurements of S, can provide information about defect density. The calculations demonstrate that defect engineering of MoS2 ML systems can be used to tune their thermoelectric performance. A need for detailed experimental studies is suggested. 2018 IOP Publishing Ltd.

Source

Journal of Physics D: Applied Physics, Vol-51, No. 30

Date

2018-01-01

Publisher

Institute of Physics Publishing

Subject

monolayer MoS₂ ; thermopower; vacancies

Coverage

Patil S.B., Department of Physics, Karnatak University, Dharwad, Karnataka, 580003, India; Sankeshwar N.S., Department of Physics, Karnatak University, Dharwad, Karnataka, 580003, India, Department of Physics, Christ University, Bangalore, Karnataka, 560029, India; Mulimani B.G., Department of Physics, Karnatak University, Dharwad, Karnataka, 580003, India

Rights

Restricted Access

Relation

ISSN: 223727; CODEN: JPAPB

Format

Online

Language

English

Type

Article

Identifier

https://doi.org/10.1088/1361-6463/aaccc8

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