Minah Seo

Unusual performances of metamaterials such as negative index of refraction, memory effect, and cloaking originate from the resonance features of the metallic composite atom(1-6). Indeed, control of metamaterial properties by changing dielectric environments of thin films below the metallic resonators has been demonstrated(7-11). However, the dynamic control ranges are still limited to less than a factor of 10,(7-11) with the applicable bandwidth defined by the sharp resonance features. Here, we

Abstract Terahertz (THz) shielding becomes increasingly important with the growing development of THz electronics and devices. Primarily materials based on carbon nanostructures or polymer–carbon nanocomposites have been explored for this application. Herein, significantly enhanced THz shielding efficiencies for 2D titanium carbide (Ti 3 C 2 MXene) thin films with nanoscale THz metamaterials are presented. Nanoscale slot antenna arrays with strong resonances at certain frequencies enhance THz el

We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our measurements we are able to reconstruct the magnetic field and, finally, the position and time-dependent Poynting vector which shows the flow of energy behind the sample. Our results show that it is possibl

We report that single-stranded deoxyribonucleic acids (ssDNAs) at very low concentrations can be detected using graphene-combined nano-slot-based terahertz (THz) resonance. A combination of the resonant structure and tuned electro-optical properties of graphene can provide unprecedentedly sensitive biomolecule sensing even using very low energy THz photons, overcoming the huge scale difference of 10,000:1 between the wavelength and the size of the ssDNAs. Ultrahigh sensitivity is obtained by the

Discrimination and quantification of trace amounts of steroid hormones in biological specimens are needed to elucidate their changing expression because their biological functions are responsible for the development and prevention of endocrine disorders. Although mass-spectrometry-based assays are most commonly recommended, development of a new type of highly sensitive and selective detection methods in clinical practices is needed. Here, we introduce a label-free type of terahertz molecule sens

We performed time-domain terahertz spectroscopy on thin layers of single-walled carbon nanotubes (SWCNTs) coated on flexible films. The SWCNT layers demonstrate good shielding of electromagnetic waves in the terahertz range while maintaining good transparency for visible light. The shielding efficiency can be engineered through the thickness control and/or chemical treatment of SWCNT layers. The frequency-dependent dielectric constants of SWCNT layers are in good agreement with the Drude free-el

Terahertz (THz) technology has become more widespread due to its diverse range of potential applications, particularly when combined with various functional metamaterials using cutting-edge nanotechnology techniques. In this report, we introduce a highly improved THz imaging technology by comparing complementary metamaterials intuitively based on Babinet’s principle. The THz reflectance spectra for the complementary metamaterials exhibit a significant and distinct association with the polarizati

We performed terahertz near-field experiments on single rectangular holes with various lengths grown on an electro-optic crystal substrate with lambda/100 resolution. We find that the near-field amplitude becomes proportionally larger as the rectangle becomes narrower, strongly suggesting that a constant energy passes through even for a very narrow slit. The occurrence of a large field enhancement at the fundamental localized resonance is discussed confirming the funneling of energy at the near-

Abstract Understanding light interaction with metallic structures provides opportunities of manipulation of light, and is at the core of various research areas including terahertz (THz) optics from which diverse applications are now emerging. For instance, THz waves take full advantage of the interaction to have strong field enhancement that compensates their relatively low photon energy. As the THz field enhancement have boosted THz nonlinear studies and relevant applications, further understan

A method for manufacturing terahertz absorber is presented. Varying fractions of graphite powder are mixed with the host poly methylmethacrylate powder and compress molded. The shielding efficiency, together with real and imaginary parts of the dielectric constant, is unambiguously determined by terahertz time domain spectroscopy in the continuous frequency range of 0.1–1.6THz. While the composites are absorptive in most of the frequency range with relatively small reflection, it turns metallic

HfO2 thin films were grown by atomic layer deposition (ALD) using a novel heteroleptic precursor, tert-butoxytris(ethylmethylamido)hafnium [HfOtBu(NEtMe)3; BTEMAH] and ozone. The structure of BTEMAH is similar to that of tetrakis(ethylmethylamido)hafnium [Hf(NEtMe)4; TEMAH] except that one of its four amido ligands is replaced with a tert-butoxy ligand. This heteroleptic structure largely improves the ALD growth rate (0.16 nm cycle−1) and Hf density (Hf mass per unit volume of HfO2 film, 7.6 g c

Recent success in the fabrication of axial and radial core-shell heterostructures, composed of one or more layers with different properties, on semiconductor nanowires (NWs) has enabled greater control of NW-based device operation for various applications. (1-3) However, further progress toward significant performance enhancements in a given application is hindered by the limited knowledge of carrier dynamics in these structures. In particular, the strong influence of interfaces between differen

We have performed ultrafast optical microscopy on single flakes of atomically thin CVD-grown molybdenum disulfide, using non-degenerate femtosecond pump-probe spectroscopy to excite and probe carriers above and below the indirect and direct band gaps. These measurements reveal the influence of layer thickness on carrier dynamics when probing near the band gap. Furthermore, fluence-dependent measurements indicate that carrier relaxation is primarily influenced by surface-related defect and trap s