4 research outputs found
Strain distribution in WS2 monolayers detected through Polarization-resolved Second Harmonic Generation
Two-dimensional (2D) graphene and graphene-related materials (GRMs) show
great promise for future electronic devices. Nevertheless, GRMs result distinct
properties under the influence of the substrate that serves as support through
uneven compression/ elongation of GRMs surface atoms. Strain in GRM monolayers
is the most common feature that alters the interatomic distances, band
structure, providing a new degree of freedom that allows regulation of their
electronic properties and introducing the field of straintronics. Having an
all-optical detection, a minimally invasive tool that rapidly probes strain in
large areas of GRM monolayers, would be of great importance in the research and
development of novel 2D devices. Here, we use Polarization-resolved Second
Harmonic Generation (P-SHG) optical imaging to identify strain distribution,
induced in a single layer of WS2 placed on a pre-patterned Si/SiO2 substrate
with cylindrical wells. By fitting the P-SHG data pixel-by-pixel, we produce
spatially resolved images of the crystal armchair direction. In regions where
the WS2 monolayer conforms to the pattern topography, a distinct cross-shaped
pattern is evident in the armchair image owing to strain. The presence of
strain in these regions is independently confirmed using a combination of
atomic force microscopy and Raman mapping
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Strain distribution in WS2 monolayers detected through polarization-resolved second harmonic generation
Two-dimensional (2D) graphene and graphene-related materials (GRMs) show great promise for future electronic devices. GRMs exhibit distinct properties under the influence of the substrate that serves as support through uneven compression/ elongation of GRMs surface atoms. Strain in GRM monolayers is the most common feature that alters the interatomic distances and band structure, providing a new degree of freedom that allows regulation of their electronic properties and introducing the field of straintronics. Having an all-optical and minimally invasive detection tool that rapidly probes strain in large areas of GRM monolayers, would be of great importance in the research and development of novel 2D devices. Here, we use Polarization-resolved Second Harmonic Generation (P-SHG) optical imaging to identify strain distribution, induced in a single layer of WS2 placed on a pre-patterned Si/SiO2 substrate with cylindrical wells. By fitting the P-SHG data pixel-by-pixel, we produce spatially resolved images of the crystal armchair direction. In regions where the WS2 monolayer conforms to the pattern topography, a distinct cross-shaped pattern is evident in the armchair image owing to strain. The presence of strain in these regions is independently confirmed using a combination of atomic force microscopy and Raman mapping.</p
RoboPol: AGN polarimetric monitoring data
Summarization: We present uniformly reprocessed and re-calibrated data from the RoboPol programme of optopolarimetric monitoring of active galactic nuclei (AGNs), covering observations between 2013, when the instrument was commissioned, and 2017. In total, the data set presented in this paper includes 5068 observations of 222 AGN with Dec. > −25○. We describe the current version of the RoboPol pipeline that was used to process and calibrate the entire data set, and we make the data publicly available for use by the astronomical community. Average quantities summarizing optopolarimetric behaviour (average degree of polarization, polarization variability index) are also provided for each source we have observed and for the time interval we have followed it.Presented on: Monthly Notices of the Royal Astronomical Societ