SKM 2023 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 5: 2D Materials I (joint session HL/CPP)

CPP 5.10: Vortrag

Montag, 27. März 2023, 12:15–12:30, POT 81

Enhancement of Light Emission in Hexagonal Boron Nitride Structures — •Felix Schaumburg, Marcel Zöllner, Vasilis Dergianlis, Stephan Sleziona, Marika Schleberger, Axel Lorke, Martin Geller, and Günther Prinz — Faculty of Physics and CENIDE, University Duisburg-Essen, Germany

Optical spectroscopy, especially Raman- and photoluminescence (PL)-spectroscopy, is commonly used to study the optical properties of 2D materials. In order to obtain the highest Raman/PL-signals, it is important to reduce the reflection of the excitation laser.

We studied a number of exfoliated hexagonal Boron Nitride (hBN) flakes with different thicknesses on a Si substrate with a 300 nm SiO₂ top layer. By changing the hBN layer thickness, we found a specific thickness, where all Raman signals (from Si, SiO₂ and hBN) showed maximum intensity, whereas the backscattered laser light was suppressed. To explain the increased intensities, we calculated the reflectivity and transmissivity of the full layer system (air, hBN, SiO₂, Si) for different hBN layer thicknesses and for different excitation wavelengths (457 nm, 532 nm, 633 nm), using the transfer-matrix-algorithm. To compare theory with experiment, we performed Raman measurements with the 3 different wavelengths on different flakes and determined their thicknesses with AFM-measurements.

Our results are in good agreement with theory and show that it is possible to choose the best flakes for spectroscopy, just by looking at their color in an optical microscope. This also allows us to easily find good flakes for observation of efficient single defect emission.