Quasi-one-dimensional (quasi-1D) materials enjoy growing interest due to their unusual physical properties and promise for miniature electronic devices. However, the mechanical exfoliation of quasi-1D materials into thin flakes and nanoribbons received considerably less attention from researchers than the exfoliation of conventional layered crystals. In this study, we investigated the micromechanical exfoliation of representative quasi-1D crystals, TiS3 whiskers, and demonstrate that they typically split into narrow nanoribbons with very smooth, straight edges and clear signatures of 1D TiS3 chains. Theoretical calculations show that the energies required for breaking weak interactions between the two-dimensional (2D) layers and between 1D chains within the layers are comparable and, in turn, are considerably lower than those required for breaking the covalent bonds within the chains. We also emulated macroscopic exfoliation experiments on the nanoscale by applying a local shear force to TiS3 crystals in different crystallographic directions using a tip of an atomic force microscopy (AFM) probe. In the AFM experiments, it was possible to slide the 2D TiS3 layers relative to each other as well as to remove selected 1D chains from the layers. We systematically studied the exfoliated TiS3 crystals by Raman spectroscopy and identified the Raman peaks whose spectral positions were most dependent on the crystals’ thickness. These results could be used to distinguish between TiS3 crystals with thickness ranging from one to about seven monolayers. The conclusions established in this study for the exfoliated TiS3 crystals can be extended to a variety of transition metal trichalcogenide materials as well as other quasi-1D crystals. The possibility of exfoliation of TiS3 into narrow (few-nm wide) crystals with smooth edges could be important for the future realization of miniature device channels with reduced edge scattering of charge carriers.
We have developed different types of photodetectors that are based on the photoionization of a gas at a low target density. The almost transparent devices were optimized and tested for online photon diagnostics at current and future x-ray free-electron laser facilities on a shot-to-shot basis with a temporal resolution of better than 100 ns. Characterization and calibration measurements were performed in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II in Berlin. As a result, measurement uncertainties of better than 10% for the photon-pulse energy and below 20 m for the photon-beam position were achieved at the Free-electron LASer in Hamburg ͑FLASH͒. An upgrade for the detection of hard x-rays was tested at the Sub-Picosecond Photon Source in Stanford.
We demonstrate scanning near-field optical microscopy with a spatial resolution below 100 nm by using low intensity broadband synchrotron radiation in the IR regime. The use of such a broadband radiation source opens up the possibility to perform nano-Fourier-transform infrared spectroscopy over a wide spectral range.
Abstract:We describe the application of scattering-type near-field optical microscopy to characterize various semiconducting materials using the electron storage ring Metrology Light Source (MLS) as a broadband synchrotron radiation source. For verifying high-resolution imaging and nano-FTIR spectroscopy we performed scans across nanoscale Si-based surface structures. The obtained results demonstrate that a spatial resolution below 40 nm can be achieved, despite the use of a radiation source with an extremely broad emission spectrum. This approach allows not only for the collection of optical information but also enables the acquisition of nearfield spectral data in the mid-infrared range. The high sensitivity for spectroscopic material discrimination using synchrotron radiation is presented by recording near-field spectra from thin films composed of different materials used in semiconductor technology, such as SiO 2 , SiC, Si x N y , and TiO 2 . ©2014 Optical Society of AmericaOCIS codes: (120.0120) Instrumentation, measurement, and metrology; (180.4243) Near-field microscopy; (240.0240) Optics at surfaces; (300.0300) Spectroscopy; (310.6860) Thin films, optical properties. 1248-1262 (2014). 5. S. Kawata and Y. Inouye, "Scanning probe optical microscopy using a metallic probe tip," Ultramicroscopy 57(2-3), 313-317 (1995). 6. F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, "Scanning interferometric apertureless microscopy: References and linksOptical imaging at 10 angstrom resolution," Science 269(5227), 1083-1085 (1995). 7. R. Bachelot, P. Gleyzes, and A. C. Boccara, "Near-field optical microscope based on local perturbation of a diffraction spot," Opt. Lett. 20(18), 1924-1926 (1995). 8. B. Knoll and F. Keilmann, "Near-field probing of vibrational absorption for chemical microscopy," Nature 399(6732), 134-137 (1999 Helm, "Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser," Phys. Rev. Lett.
The Metrology Light Source (MLS), the new electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB) located in Berlin, is dedicated to metrology and technological developments in the UV and extreme UV spectral range as well as in the IR and THz region. The MLS can be operated at any electron beam energy between 105 and 630 MeV and at electron beam currents varying from 1 pA (one stored electron) up to 200 mA. Moreover, it is optimized for the generation of coherent synchrotron radiation in the far IR/THz range. Of special interest for PTB is the operation of the MLS as a primary radiation source standard from the near IR up to the soft x-ray region. Therefore, the MLS is equipped with all the instrumentation necessary to measure the storage ring parameters and geometrical parameters needed for the calculation of the spectral photon flux according to the Schwinger theory with low uncertainty.
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