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- 实验方案
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Deeply subwavelength phonon-polaritonic crystal made of a van der Waals material
摘要： Photonic crystals (PCs) are periodically patterned dielectrics providing opportunities to shape and slow down the light for processing of optical signals, lasing and spontaneous emission control. Unit cells of conventional PCs are comparable to the wavelength of light and are not suitable for subwavelength scale applications. We engineer a nanoscale hole array in a van der Waals material (h-BN) supporting ultra-confined phonon polaritons (PhPs)—atomic lattice vibrations coupled to electromagnetic fields. Such a hole array represents a polaritonic crystal for mid-infrared frequencies having a unit cell volume of 10??λ?3 (with λ? being the free-space wavelength), where PhPs form ultra-confined Bloch modes with a remarkably flat dispersion band. The latter leads to both angle- and polarization-independent sharp Bragg resonances, as verified by far-field spectroscopy and near-field optical microscopy. Our findings could lead to novel miniaturized angle- and polarization-independent infrared narrow-band couplers, absorbers and thermal emitters based on van der Waals materials and other thin polar materials.
关键词： van der Waals material,near-field microscopy,phonon-polaritonic crystal,mid-infrared,hexagonal boron nitride,Bragg resonance
更新于2025-09-23 15:23:52
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[OSA CLEO: Science and Innovations - San Jose, California (2014..-..)] CLEO: 2014 - Terahertz near-field phase contrast imaging
摘要： We demonstrate a method, permitting the observation of dielectric loading of hydrocarbons into a porous coordination polymer nanocrystal (PCP), by spatially resolving the phase difference between the near-field responses of two terahertz resonators.
关键词： Near-field microscopy,terahertz,Spectroscopy,Metamaterials
更新于2025-09-23 15:22:29
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Sb <sub/>2</sub> Te <sub/>3</sub> growth study reveals: Formation of Nanoscale Charge Carrier Domains Is an Intrinsic Feature Relevant for Electronic Applications
摘要： Sb2Te3 exhibits a plethora of fundamentally relevant electronic phenomena enabling electronic phase change memory cells, thermoelectric devices and three-dimensional topological insulator structures. Thus, the controlled growth of nanostructures and thin films with well-defined electronic properties is of uttermost importance. Previously, our group observed symmetric infrared domains in hexagonal Sb2Te3 nanoplatelets from a solvothermal chemical synthesis. The relative optical contrast observed was indirectly linked to the formation of regions with different defect densities (charge carrier concentrations). This raises two major questions, which we answer in this study: Is the domain formation restricted to the specific platelet growth process? No! Do the infrared spectra of both domains really follow a ‘Drude-like’ free charge carrier response? Yes! By controlling the initial water concentration, we promote the growth of the nanoplatelets in c-direction and tune the morphology from platelet-like to octahedra-like. Although the growth mode changes from spiral growth to layer-by-layer, similar infrared domains are identified using scattering-type scanning near-field optical microscopy (s-SNOM). Furthermore, we also reproduced the formation of symmetric infrared domains in thin, high quality crystalline films grown using molecular beam epitaxy (MBE). Normalized infrared near-field spectra of smaller Sb2Te3 nanoparticles reveal a relative shift of the plasma frequency in both domains. These findings demonstrate that the formation of domains with different charge carrier properties is an intrinsic material property of Sb2Te3 and might strongly influence all of its electronic applications.
关键词： infrared near-field microscopy,Antimony telluride,domain formation,van der Waals materials,transition metal dichalcogenides,epitaxial growth
更新于2025-09-23 15:21:21
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Imaging Carrier Inhomogeneities in Ambipolar Tellurene Field Effect Transistors
摘要： Developing van der Waals (vdW) homojunction devices requires materials with narrow bandgaps and simultaneously high hole and electron mobilities for bipolar transport, as well as methods to image and study spatial variations in carrier type and associated conductivity with nanometer spatial resolution. Here we demonstrate the general capability of near-field scanning microwave microscopy (SMM) to image and study the local carrier type and associated conductivity in operando by studying ambipolar field effect transistors (FETs) of the 1D vdW material tellurium in 2D form. To quantitatively understand electronic variations across the device, we produce nanometer resolved maps of the local carrier equivalence backgate voltage. We show that the global device conductivity minimum determined from transport measurements does not arise from uniform carrier neutrality, but rather from the continued coexistence of p-type regions at the device edge and n-type regions in the interior of our micron-scale devices. This work both underscores and addresses the need to image and understand spatial variations in the electronic properties of nanoscale devices.
关键词： 2D Materials,Field-Effect Transistor,Microwave,Near-Field Microscopy,Atomic Force Microscope
更新于2025-09-19 17:15:36
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - The terahertz near-field response of graphene layers and graphene structures
摘要： We report on the experimental study of the scattering and the near-field interaction of a THz electromagnetic field with graphene layers near the probe of a terahertz near-field microscope. There are resonance lines in the spectrum for a graphene monolayer-based transistor structure, which is possibly due to the strong plasmon response at terahertz frequencies and the manifestation of plasmon interference in the graphene strip.
关键词： terahertz,near-field microscopy,graphene,plasmon response
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Enhanced Subwavelength Coupling and Nanofocusing with Fiber-Plasmonic Hybrid Probe
摘要： Metallic nanowires supporting surface plasmon polaritons can localize optical fields at nanoscale for near-field imaging. In this paper, we propose a photonic-plasmonic probe for nanoscale light confinement. The linearly polarized fiber mode is asymmetrically coupled to radial plasmons to create hot-spot at the tip apex.
关键词： nano-antenna,surface plasmon polaritons,optical fiber,near-field microscopy,mode conversion
更新于2025-09-11 14:15:04