Electronic devices based on the 2D material black phosphorous - layer-dependent properties

• Applicants: Dr.-Ing. Andreas Hutzler; Professor Dr. Vojislav Krstic
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Synthesis and Properties of Functional Materials
• Term: from 2020 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 454726051

• Final Report Year: 2024

Final Report Abstract

2D materials exhibit electrical and optical properties which make them extremely interesting for novel electron devices: High carrier mobilities promise capability of high currents and the energy-level transitions, which often are direct transitions, are important for the design of optoelectronic devices. To fully make use of these advantages, characterizing 2D materials is of great importance, especially determining their thickness; therefore, this was a major part of the project. With optical microspectroscopy a method could be established which enables thickness determination in a simple way and at the same time guarantees small lateral dimensions of the measurement spot – an essential demand when working with small flakes of 2D materials. For microspectroscopy, a simple microscope coupled with a spectrometer via a glass fiber is sufficient. With this setup the wavelength dependent reflection of a layer stack containing a substrate, the 2D material and a possible passivation is measured. The high lateral resolution is given using objective lenses with high magnification (100x). The recorded reflectance spectrum is then compared with a modeled spectrum. The modeling considers material properties as well as the numerical aperture (NA) of the objective lenses, which has an enormous influence on the outcome. The thickness of the layer of interest in the model is now varied until the deviation of the modeled spectrum and the measured spectrum becomes minimal. This value is considered as the actual thickness. Further points investigated in the project were the technological interaction and application of 2D materials when building electron devices, for example dielectrics or passivation. Here, the differences to established semiconductor technology are significant.

Publications

• Correlating Optical Microspectroscopy with 4×4 Transfer Matrix Modeling for Characterizing Birefringent Van der Waals Materials. Small Methods, 7(10).
  Schwarz, Julian; Niebauer, Michael; Koleśnik‐Gray, Maria; Szabo, Maximilian; Baier, Leander; Chava, Phanish; Erbe, Artur; Krstić, Vojislav; Rommel, Mathias & Hutzler, Andreas
  
• Unconventional conductivity increase in multilayer black phosphorus. npj 2D Materials and Applications, 7(1).
  Koleśnik-Gray, Maria; Meingast, Laura; Siebert, Martin; Unbehaun, Tim; Huf, Tobias; Ellrott, Günter; Abellán, Gonzalo; Wild, Stefan; Lloret, Vicent; Mundloch, Udo; Schwarz, Julian; Niebauer, Michael; Szabo, Maximilian; Rommel, Mathias; Hutzler, Andreas; Hauke, Frank; Hirsch, Andreas & Krstić, Vojislav
  
• Spectro‐Spatial Unmixing in Optical Microspectroscopy for Thickness Determination of Layered Materials. Advanced Optical Materials, 13(5).
  Schwarz, Julian; Niebauer, Michael; Römling, Lukas; Pham, Adrian; Koleśnik‐Gray, Maria; Evanschitzky, Peter; Vogel, Nicolas; Krstić, Vojislav; Rommel, Mathias & Hutzler, Andreas