Scientific Output

Link to project open research data repository: ZENODO

Fundamentals of cathodoluminescence in a STEM: The impact of sample geometry and electron beam energy on light emission of semiconductors by Michael Stöger-Pollach, Kristýna Bukvišová, Sabine Schwarz, Michal Kvapil, Tomáš Šamořil and Michal Horák

Ultramicroscopy Volume 200, May 2019, Pages 111-124
DOI: 10.1016/j.ultramic.2019.03.001 

Link to Open access version (preprint): ZENODO or ArXiv

Link to ORDP experimental dataset 

Abstract:

Cathodoluminescence has attracted interest in scanning transmission electron microscopy since the advent of commercial available detection systems with high efficiency, like the Gatan Vulcan or the Attolight Mönch system. In this work we discuss light emission caused by high-energy electron beams when traversing a semiconducting specimen. We nd that it is impossible to directly interpret the spectrum of the emitted light to the inter-band transitions excited by the electron beam, because the Čerenkov effect and the related light guiding modes as well as transition radiation is altering the spectra. Total inner re ection and subsequent interference effects are changing the spectral shape dependent on the sample shape and geometry, sample thickness, and beam energy, respectively. A detailed study on these parameters is given using silicon and GaAs as test materials.

Formation of Tungsten Oxide Nanowires by Electron-Beam-Enhanced Oxidation of WS2 Nanotubes and Platelets by Miroslav Kolíbal, Kristýna Bukvišová, Lukáš Kachtík, Alla Zak, Libor Novák, and Tomáš Šikola  

J. Phys. Chem. C, DOI: 10.1021/acs.jpcc.9b00592, March 9 2019  

Link to Open access version (preprint)

Link to ORDP experimental dataset 

Abstract:

Oxidation of van der Waals-bonded layered semiconductors plays a key role in deterioration of their superior optical and electronic properties. The oxidation mechanism of these materials is, however, different from non-layered semiconductors in many aspects. Here, we show a rather unusual oxidation of tungsten disulfide (WS2) nanotubes and platelets in a high vacuum chamber at a presence of water vapor and at elevated temperatures. The process results in formation of small tungsten oxide nanowires on the surface of WS2. Utilizing real-time scanning electron microscopy we are able to unravel the oxidation mechanism, which proceeds via reduction of initially formed WO3 phase into W18O49 nanowires. Moreover, we show that the oxidation reaction can be localized and enhanced by an electron beam irradiation, which allows for on-demand growth of tungsten oxide nanowires.