Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Keiser, George R.; Klarskov, Pernille

doi:10.3390/photonics6010022

Cited by 21 publications

(12 citation statements)

References 170 publications

(242 reference statements)

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“…[54] Recently, this scheme was extended to optical pump-multi-THz probe measurements: an ultrafast formation of carrier depletion layer in InAs nanowires was observed with 10 nm spatial and 50 fs temporal resolution. [58]; further aspects of ultrafast dynamics in single nanostructures are discussed in ref. [56] Concentration of THz radiation (although not to a single structure) may be achieved also using metallic nanoslits, nanoantennas or metamaterials.…”

Section: Experiments For the Determination Of Thz Conductivitymentioning

confidence: 99%

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Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

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Transport of charges is a fundamental process in many high-tech applications including photovoltaic or optoelectronic devices, but also in more ordinary components such as unsophisticated wires and other circuitry. The development of nanotechnologies resulted in the fabrication of highly complex materials consisting of a large variety of nanosized elements, which inevitably involve a multitude of charge transport processes occurring on various time-and length-scales. Figure 1 summarizes the most common nanoelements with high application potential.For example, the electrodes employed in Grätzel solar cells [1] are composed of percolated networks of a huge number of metal oxide nanoparticles (top-left panel in Figure 1). Colloidal nanocrystals form the basis for thin film electronics and flexible electronic devices. [2] The synthetic approaches control their composition, size and electronic structure (energy levels, density of states within the bands and in the bandgap) and the charge-carrier transport. [2,3] Nanowires and nanotubes made of conventional semiconductors are quasi 1D systems combining Terahertz spectroscopy has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes or 2D crystals. Its great importance stems from the fact that it is a noncontact method and, owing to its high frequency and broadband character, it is capable of characterizing charge transport properties within individual nano-objects but also among them. In addition, probing of photoinitiated ultrafast charge dynamics is possible thanks to the sub-picosecond time resolution. Despite this unprecedented potential, the interpretation of the measured terahertz conductivity spectra in many materials is still intensively debated. Herein is presented a review of the experiments performed on nanostructures of conventional semiconductors and on carbon nanomaterials (graphene and carbon nanotubes) during the past decade. The state of the art of the theoretical formalism is provided and discussed, including the intrinsic response, as well as the role of inherent heterogeneity and of the experimental conditions.

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Section: Experiments For the Determination Of Thz Conductivitymentioning

confidence: 99%

“…A more detailed review of these approaches is presented in ref. [58]; further aspects of ultrafast dynamics in single nanostructures are discussed in ref. [59].…”

Section: Experiments For the Determination Of Thz Conductivitymentioning

confidence: 99%

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Kužel

Němec

2019

Advanced Optical Materials

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“…Generally, there is a need for refined theoretical and numerical models to explain and design tunable materials and composites with tailored nonlinear properties. Note that the general method followed by our coupled model could be applied to other type of tunable systems where local field enhancement and amplification is relevant, including for example ferromagnetic metamaterials 21 , liquid crystals based devices 22 , or field-enhanced carrier dynamics in doped semiconductors at other frequency ranges, particularly in the THz and near-infrared 23,24 .…”

Section: Introductionmentioning

confidence: 99%

Enhanced tunability in ferroelectric composites through local field enhancement and the effect of disorder

Vial

Hao

2019

Journal of Applied Physics

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We investigate numerically the homogenized permittivities of composites made of low index dielectric inclusions in a ferroelectric matrix under a static electric field. A refined model is used to take into account the coupling between the electrostatic problem and the electric field dependent permittivity of the ferroelectric material, leading to a local field enhancement and permittivity change in the ferroelectric. Periodic and pseudo-random structures in two dimensions are investigated and we compute the effective permittivity, losses, electrically induced anisotropy and tunability of those metamaterials. We show that the tunability of such composites might be substantially enhanced in the periodic case, whereas introducing disorder in the microstructure weaken the effect of enhanced local permittivity change. Our results may be useful to guide the synthesis of novel composite ceramics with improved characteristics for controllable microwave devices.

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“…Keiser et al presented advances in THz science and technology that rely on confining the energy of incident THz radiation to small, very subwavelength-sized regions with a focus on two broad areas of application for such field confinement: metamaterial-based nonlinear THz devices and THz near-field microscopy and spectroscopy techniques. 206 Wang et al reviewed the field of THz modulators based on different kinds of dynamic tunable metasurfaces combined with semiconductors, 2D electron gas heterostructures, superconductors, phase-transition materials, graphene, and other 2D material. 207 Graphene is a critical material related to the success of THz modulation due to how graphene plasmon resonances have remarkably large oscillator strengths, resulting in prominent roomtemperature optical absorption peaks compared to the low temperature requirements for other 2D electron gases.…”

Section: Thz Conductivitymentioning

confidence: 99%

Review of THz-based semiconductor assurance

True

Jessurun

et al. 2021

Opt. Eng.

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Terahertz radiation for inspection and fault detection has been of interest for the semiconductor industry since the first generation and detection of THz signals. Until recent hardware advances, THz systems lacked the signal quality and reliability for use as an effective nondestructive testing (NDT) method. Incremental advances in THz sources, detectors, and signal processing resulted in the successful applied-industrial use of THz NDT techniques on carbon fiber laminates, automotive coatings, and for detection of counterfeit pharmaceutical tablets. Semiconductor inspection and verification methods ensure the functionality and thereby safety of vital electronics for several critical industries. For this reason, the reliability and verification of a THz NDT method must exceed currently used inspection systems. With recent laboratory access to THz radiation, THz inspection methods are often compared with existing optical, electrical, and volumetric semiconductor verification techniques for their production monitoring and failure analysis viability. This review will cover THz techniques and their applications at the printed circuit board (PCB), integrated circuit (IC), and transistor/gate scales. The THz radiation gap spans between optical and electronic ranges with a millimeter-sized wavelength allowing for adequate penetration of plastic and ceramic and semiconductor materials. THz radiation can be used to determine structural features, electrical signatures in the THz range, and chemical information simultaneously. Cost and environmental limitations restricted the ability for THz NDT semiconductor inspection methods to escape the lab and succeed in the dynamic environment of a semiconductor fabrication environment. Hybridized metrology methods incorporating information from multiple inspection tools are a regime where THz spectral and structural data can be combined with existing methods such as optical, x-ray, or E-beam. THz can be used initially to offer support to the complex failure analysis and verification requirements of the semiconductor industry from nanoscale to macroscale features and components. For THz systems to become independent inspection tools used for semiconductor production monitoring, in the lab or fab, this will require a confident level of statistical process control for THz signal generation, detection, or processing. Applied industrial semiconductor device inspection will likely be a result of a combination of research into THz hardware, reconstruction techniques, and the widespread application of machine learning techniques. Many breakthroughs occurred over the years to enable successful nondestructive characterization and inspection of semiconductor devices from the nanoscale transistors to fully packaged integrated circuits and assembled PCBs.

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Terahertz Field Confinement in Nonlinear Metamaterials and Near-Field Imaging

Cited by 21 publications

References 170 publications

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Terahertz Spectroscopy of Nanomaterials: a Close Look at Charge‐Carrier Transport

Enhanced tunability in ferroelectric composites through local field enhancement and the effect of disorder

Review of THz-based semiconductor assurance

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