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Photoluminescence from monolayer semiconductors in dielectric environments
In their monolayer form TMDCs have a direct band gap [1], which results in photoemission when excited by laser light. The photoluminescence yield strongly depends on the dielectric environment, such as the substrate on which the TMDC is placed.
Transition Metal Dichalcogenides (TMDCs) belong to the class of two-dimensional (2D) materials, a group of layered materials that can be thinned down to a single atomic layer (monolayer). In their monolayer form TMDCs have a direct band gap [1], which results
in photoemission when excited by laser light. The photoluminescence yield strongly depends on the dielectric environment, such as the substrate on which the TMDC is placed. A favorable substrate material is hexagonal boron nitride (h-BN), a 2D insulator with atomically flat surfaces. The luminescence yield from a TMDC monolayer can be
resonantly enhanced by the h-BN thickness and geometry [2].
The goal of this project is to characterize the influence of the h-BN substrate on the PL of the monolayer. By choosing the h-BN thickness such that the emission wavelength can constructively interfere with itself, the efficiency of the detected light might be enhanced. For a comparison, different h-BN thicknesses and other substrates should be analysed.
Overall the student will: 1) Fabricate the structures with typical process steps like exfoliation and stacking of 2D materials. 2) Perform spectroscopic measurements in an optical setup. 3) Analyse the measured data and develop models for comparison with theory.
References:
[1] A. Splendiani et al., Nano Letters 10, 1271–1275 (2010).
[2] A. Jain et al., Nano Letters 19, 6914–6923 (2019).
[3] H. Goncalves de Medeiros, ongoing semester project in the Photonics group at ETH (2020).
Prerequisites:
Practical lab skills, basic programming skills for data analysis and basic knowledge on electromagnetic fields.
Transition Metal Dichalcogenides (TMDCs) belong to the class of two-dimensional (2D) materials, a group of layered materials that can be thinned down to a single atomic layer (monolayer). In their monolayer form TMDCs have a direct band gap [1], which results in photoemission when excited by laser light. The photoluminescence yield strongly depends on the dielectric environment, such as the substrate on which the TMDC is placed. A favorable substrate material is hexagonal boron nitride (h-BN), a 2D insulator with atomically flat surfaces. The luminescence yield from a TMDC monolayer can be resonantly enhanced by the h-BN thickness and geometry [2]. The goal of this project is to characterize the influence of the h-BN substrate on the PL of the monolayer. By choosing the h-BN thickness such that the emission wavelength can constructively interfere with itself, the efficiency of the detected light might be enhanced. For a comparison, different h-BN thicknesses and other substrates should be analysed. Overall the student will: 1) Fabricate the structures with typical process steps like exfoliation and stacking of 2D materials. 2) Perform spectroscopic measurements in an optical setup. 3) Analyse the measured data and develop models for comparison with theory.
References: [1] A. Splendiani et al., Nano Letters 10, 1271–1275 (2010). [2] A. Jain et al., Nano Letters 19, 6914–6923 (2019). [3] H. Goncalves de Medeiros, ongoing semester project in the Photonics group at ETH (2020).
Prerequisites: Practical lab skills, basic programming skills for data analysis and basic knowledge on electromagnetic fields.