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Open AccessArticle

Facile and Reliable Thickness Identification of Atomically Thin Dichalcogenide Semiconductors Using Hyperspectral Microscopy

1
Department of Electrical Engineering, National Changhua University of Education, Changhua 500, Taiwan
2
Department of Electronic Engineering, National Changhua University of Education, Changhua 500, Taiwan
*
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(3), 526; https://doi.org/10.3390/nano10030526
Received: 13 February 2020 / Revised: 7 March 2020 / Accepted: 12 March 2020 / Published: 14 March 2020
(This article belongs to the Special Issue 2D Materials and Their Heterostructures and Superlattices)
Although large-scale synthesis of layered two-dimensional (2D) transition metal dichalcogenides (TMDCs) has been made possible, mechanical exfoliation of layered van der Waals crystal is still indispensable as every new material research starts with exfoliated flakes. However, it is often a tedious task to find the flakes with desired thickness and sizes. We propose a method to determine the thickness of few-layer flakes and facilitate the fast searching of flakes with a specific thickness. By using hyperspectral wild field microscopy to acquire differential reflectance and transmittance spectra, we demonstrate unambiguous recognition of typical TMDCs and their thicknesses based on their excitonic resonance features in a single step. Distinct from Raman spectroscopy or atomic force microscopy, our method is non-destructive to the sample. By knowing the contrast between different layers, we developed an algorithm to automatically search for flakes of desired thickness in situ. We extended this method to measure tin dichalcogenides, such as SnS2 and SnSe2, which are indirect bandgap semiconductors regardless of the thickness. We observed distinct spectroscopic behaviors as compared with typical TMDCs. Layer-dependent excitonic features were manifested. Our method is ideal for automatic non-destructive optical inspection in mass production in the semiconductor industry. View Full-Text
Keywords: 2D materials; transition metal dichalcogenides (TMDCs); hyperspectral microscopy; thickness identification; MoS2; MoSe2; WS2; WSe2; SnS2; SnSe2 2D materials; transition metal dichalcogenides (TMDCs); hyperspectral microscopy; thickness identification; MoS2; MoSe2; WS2; WSe2; SnS2; SnSe2
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MDPI and ACS Style

Chang, Y.-C.; Wang, Y.-K.; Chen, Y.-T.; Lin, D.-Y. Facile and Reliable Thickness Identification of Atomically Thin Dichalcogenide Semiconductors Using Hyperspectral Microscopy. Nanomaterials 2020, 10, 526.

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