Modeling of the Optical Properties of Monolayer WS 2
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Modeling of the Optical Properties of Monolayer WS2 Tae Jung Kim∗ Center for Converging Humanities, Kyung Hee University, Seoul 02447, Korea and Department of Physics, Kyung Hee University, Seoul 02447, Korea
Van Long Le† and Hoang Tung Nguyen Department of Physics, Kyung Hee University, Seoul 02447, Korea and Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam
Xuan Au Nguyen and Young Dong Kim‡ Department of Physics, Kyung Hee University, Seoul 02447, Korea (Received 8 July 2020; Revised 10 July 2020; accepted 10 July 2020) We report parametric modeling of the optical properties of monolayer WS2 so its dielectric response can be calculated at temperatures from 41 to 300 K from 1.5 to 6 eV. Parameterization of dielectric function was performed by dielectric-function parametric model, using previously reported dielectric function data which was obtained by spectroscopic ellipsometry. We interpolated the obtained parameters by using cubic polynomials to reconstruct optical properties at arbitrary temperatures. Blue shifts of the bandgap energies and reductions of linewidths of the critical point structures are clearly observed. Given these results, refractive indices and absorption coefficients of the monolayer WS2 follow also at arbitrary temperatures. Keywords: Monolayer WS2 , Optical properties, Dielectric-function parametric model, Spectroscopic ellipsometry DOI: 10.3938/jkps.77.298
I. INTRODUCTION Transition-metal dichalcogenides (TMDCs) have drawn much attention by displaying distinctive properties related to their low dimensionality [1–4]. Among TMDC materials, WS2 is well known as a suitable replacement for silicon or organic materials in polarized resonant emission [3], spin-valley coupling [5], and gate-tunable thermoelectric effect [6] applications, and for high quantum yields in a 2D system [7,8]. Dielectric functions = 1 + i2 of WS2 , as well as their temperature dependences, are necessary to design devices for these applications [9]. As a consequence, of monolayer WS2 has been investigated by several groups [10–12] at various temperatures. However, optical properties at arbitrary working temperature are imperative to design better devices. Here, we use the dielectric-function parametric model (DFPM) [13,14] to represent the dielectric function of WS2 . This model is widely used to describe the dielectric functions ∗ These authors contributed equally to this work.; [email protected] † These authors contributed equally to this work. ‡ E-mail: [email protected]
pISSN:0374-4884/eISSN:1976-8524
of semiconductors [15–18], as measured using spectroscopic ellipsometry (SE) which is an excellent technique to observe the optical properties of materials [19–22]. Specifically, we use values from Ref. 12 to obtain parameterized coefficients. These coefficients are fit to cubic polynomials to allow the dielectric function of WS2 to be calculated at photon energies from 1.5 to 6.0 eV and at arbitrary temperatures from 41 to 300 K.
II. MODELING
The DFPM reconstructs as the
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