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- ItemLattice matched Volmer–Weber growth of Fe3Si on GaAs(001) - the influence of the growth rate(Bristol : IOP Publ., 2019) Jenichen, B.; Cheng, Z.; Hanke, M.; Herfort, J.; Trampert, A.We investigate the formation of lattice matched single-crystalline Fe3Si/GaAs(001) ferromagnet/semiconductor hybrid structures by Volmer-Weber island growth, starting from the epitaxial growth of isolated Fe3Si islands up to the formation of continuous films as a result of island coalescence. We find coherent defect-free layers exhibiting compositional disorder near the Fe3Si/GaAs - interface for higher growth rates, whereas they are fully ordered for lower growth rates. © 2019 IOP Publishing Ltd.
- ItemTerahertz quantum-cascade lasers for high-resolution absorption spectroscopy of atoms and ions in plasmas(Bristol : IOP Publ., 2023) Lü, X.; Röben, B.; Biermann, K.; Wubs, J.R.; Macherius, U.; Weltmann, K.-D.; van Helden, J.H.; Schrottke, L.; Grahn, H.T.We report on terahertz (THz) quantum-cascade lasers (QCLs) based on GaAs/AlAs heterostructures, which exhibit single-mode emission at 3.360, 3.921, and 4.745 THz. These frequencies are in close correspondence to fine-structure transitions of Al atoms, N+ ions, and O atoms, respectively. Due to the low electrical pump power of these THz QCLs, they can be operated in a mechanical cryocooler in continuous-wave mode, while a sufficient intrinsic tuning range of more than 5 GHz is maintained. The single-mode operation and the intrinsic tuning range of these THz QCLs allow for the application of these lasers as radiation sources for high-resolution absorption spectroscopy to determine the absolute densities of Al atoms, N+ ions, and O atoms in plasmas.