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Quasi-1D TiS <sub/>3</sub> Nanoribbons: Mechanical Exfoliation and Thickness-Dependent Raman Spectroscopy
摘要： 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.
关键词： transition metal trichalcogenides,quasi-one-dimensional materials,scanning near-field optical microscopy,Raman spectroscopy,mechanical exfoliation
更新于2025-09-23 15:21:21
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Near-field infrared investigations of an arm-terminated spiral structure with bow-tie probe
摘要： A detailed analysis of micro- and nanoantennas is crucial for enhancing the performance of photodetectors in the mid- and far-infrared (IR) region. In contrast to the rapid progress in IR detectors based on nanodevices, the local nanoscale properties of antennas for the purpose of near-field coupling with these detectors have not been well investigated. In this work, we fabricated and studied a logarithm-spiral (log-spiral) antenna with an arm termination, which was designed as a low-loss, wide-band antenna for highly efficient near-field interaction with nanoscale IR detectors. By using a scattering-type near-field optical microscope (s-SNOM) combined with a highly stable quantum cascade laser, we observed a nanoscale spatial distribution of amplitudes generated via IR illumination on the antenna surface. Experimental and simulated results revealed a clear dependence on IR-light polarization corresponding to the rotationally symmetric structure of the spiral antenna. Furthermore, phase mapping measurements indicated a π reversal of the out-of-plane phase between two adjacent antenna probes regardless of polarization direction, providing a possibility of efficient near-field coupling with nanoscale detectors. These results demonstrate that s-SNOM imaging offers a powerful tool for gaining useful information regarding mutual coupling between optical antennas and nanostructures.
关键词： scanning near-field optical microscopy,optical phase,infrared
更新于2025-09-19 17:15:36
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Near-field infrared microscopy of nanometer-sized nickel clusters inside single-walled carbon nanotubes
摘要： Nickel nanoclusters grown inside single-walled carbon nanotubes (SWCNT) were studied by infrared scattering-type scanning near-field optical microscopy (s-SNOM). The metal clusters give high local contrast enhancement in near-field phase maps caused by the excitation of free charge carriers. The experimental results are supported by calculations using the finite dipole model, approximating the clusters with elliptical nanoparticles. Compared to magnetic force microscopy, s-SNOM appears much more sensitive to detect metal clusters inside carbon nanotubes. We estimate that these clusters contain fewer than 700 Ni atoms.
关键词： s-SNOM,infrared scattering-type scanning near-field optical microscopy,magnetic force microscopy,single-walled carbon nanotubes,Nickel nanoclusters
更新于2025-09-16 10:30:52
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Nanoapertures without nanolithography
摘要： We propose and experimentally demonstrate the implementation of lithography-free nano-apertures on optical fibers. By sputtering metallic nanofilms onto the end face of step index fibers that contain central nano-channels, fiber-integrated nano-apertures are instantaneously implemented without the use of any kind of lithographic step. In accordance with simulations, the experiments show diffraction-limited nano-spots in the far-field at the location of the nano-aperture for sufficiently thick films. We reproducibly implement a series of devices by sputtering Al and Pt nano-films, reaching aperture diameters as small as 40 nm and showing spectrally broadband operation. Due to its simplicity, scalability and potential for large-scale production the nano-aperture enhanced fiber concept will be highly relevant for lab-on-a-fiber applications and for the development of future fiber-based nano-probes with high spatial resolutions.
关键词： lab-on-a-fiber,hybrid fibers,nanofabrication,scanning near-field optical microscopy (SNOM),nanoapertures
更新于2025-09-04 15:30:14