Tzu-Hung Chuang

High performance midinfrared narrow-band plasmonic thermal emitter

The blackbody radiation spectrum is fundamental to any thermal emitter. However, by properly designing the emitter structure, a narrow bandwidth and high power infrared source can be achieved. This invention consists of a triple layer structure by sandwiching a dielectric SiO2 layer between two Ag metal films on the Si substrate. The top Ag layer is perforated by periodic holes. When the device was heated, the background thermal radiation was suppressed by the bottom Ag whose emissivity is very low. The thermal radiation generated in the SiO2 layer resonant between two metal films and the Ag∕SiO2 and the Ag/air surface plasmon polaritons are induced and converted to light radiation. Strong resonance at Ag∕SiO2 (1,0) degenerate modes results in the coherent light radiation at the wavelength associated with the dielectric constant of SiO2 and the lattice constant of the perforated hole array. The ratio of the full width at half maximum to the peak wavelength is 0.114. This narrow bandwidth and high power in...

Extraordinary transmission through a silver film perforated with cross shaped hole arrays in a square lattice

In this work, the transmission through cross shaped hole with different sizes but the same lattice constant was measured with the polarized light to investigate the variation of localized charge oscillation around the hole. The comparison between the transmission intensities through the similarly arranged periodic hole array with different hole shapes, i.e., cross, square, and rectangular, were also measured. The cross shaped hole gives rise to a larger transmission of light than those perforated with square or rectangular hole.

Electronic structure of the carbon nanotube tips studied by x-ray-absorption spectroscopy and scanning photoelectron microscopy

Angle-dependent x-ray absorption near edge structure (XANES) and scanning photoelectron microscopy (SPEM) measurements have been performed to differentiate local electronic structures of the tips and sidewalls of highly aligned carbon nanotubes. The intensities of both π*- and σ*-band C K-edge XANES features are found to be significantly enhanced at the tip. SPEM results also show that the tips have a larger density of states and a higher C 1s binding energy than those of sidewalls. The increase of the tip XANES and SPEM intensities are quite uniform over an energy range wider than 10 eV in contrast to earlier finding that the enhancement is only near the Fermi level.

Oxidation states in scanning-probe-induced Si3N4 to SiOx conversion studied by scanning photoemission microscopy

The biased conductive probe of an atomic force microscope can induce local oxidation in ambience for converting silicon nitride films to silicon oxides with high reaction rate. Spatially resolved photoemission analysis with submicron resolution has been utilized to study the oxidation states of converted silicon oxide patterns in comparison with the surrounding Si3N4 layer. The core level shift of the Si 2p photoelectron peak and the spectral features in the valence band reveal a complete conversion of silicon nitride to silicon oxide at a bias voltage of 10 V, with no remaining nitrogen left. The major oxide is SiO2. The observed oxidation states of Si4+, Si3+, and Si2+ show a gradient depth distribution indicating excess silicon in the layer.

Dispersion of surface plasmon polaritons on silver film with rectangular hole arrays in a square lattice

Extraordinary optical transmission through a two-dimensional Ag film in the far infrared region was demonstrated. The holes were rectangular and arranged in a square lattice. When either the width or the length size of the rectangular holes was close to the half of the lattice constant a∕2, the degenerate (±1,0) Ag∕Si or (0,±1) Ag∕Si modes split into two peaks. Additionally, the surface plasmon dispersion relations of the square hole array with different aspect ratios of holes were measured. As the aspect ratio increased, the surface plasmon tended to couple strongly with the local charge dipole oscillations in a direction perpendicular to the long edges. The charge dipole oscillation parallel to the long edges gradually disappeared. This is confirmed by experiments using the polarized light. The dynamic properties of the surface plasmon dispersion relations show the interaction among localized surface plasmons and its mechanism.

Bragg scattering of surface plasmon polaritons on extraordinary transmission through silver periodic perforated hole arrays

Extraordinary optical transmission through a two-dimensional periodic perforated Ag film in the far infrared region was demonstrated. When the squared hole size is close to a half lattice constant a∕2, the split of the degenerate (±1,0) Ag∕Si and (0,±1) Ag∕Si modes into two peaks becomes apparent. Surface plasmon polaritons dispersion relations with variously sized square holes are measured to investigate the different surface charge fields at the periodic metal array. Strong scattering of the forward SPP waves, in the (1,0) Ag∕Si mode, leads to a much lower transmission than that of in the (−1,0) Ag∕Si mode. Experimental results demonstrate that the photonic band gap opens up when the size of the squared hole exceeds a half lattice constant a∕2.

Zone-Plate-Based Scanning Photoelectron Microscopy At Srrc: Performance And Applications

Adapting classical spectroscopic methods to the new challenge of studying nanomaterials, imaging techniques are the trendsetter in recent years. Among them is scanning photoelectron microscopy (SPEM) with submicron spatial resolution, where the sample surface is raster-scanned by a focused soft X-ray beam, and the emitted photoelectrons are collected at each point by the input optics of an electron energy analyzer. We have constructed such a station at SRRC in Taiwan, which is now fully in operation. In this paper, we introduce the specific features of the instrument and discuss application examples on the characterization of scanning-probe-induced Si3N4 to SiOx conversion and electron- and plasma-induced chemical changes in alkanethiols self-assembled monolayers. In combining two-dimensional imaging and micro-photoemission, SPEM can reveal valuable information on the chemical and electronic properties of structured and multiphase materials.

Remotely coupled surface plasmons in a metal/insulator/Si structure perforated with periodic square hole arrays

The zero-order transmission of radiation through a metal/dielectric structure perforated with square hole arrays is strongly enhanced when incident light resonates with surface plasmons (SPs). Surprisingly, when a metal/dielectric double layer, such as Ag∕SiO2, is fabricated on a silicon substrate, the Ag∕Si SP mode by coupling Ag and Si across the intermediate dielectric film has been found. It is named the remotely coupled surface plasmon. The transmission intensity is investigated as a function of the intermediate SiO2 thickness. The coupling lengths between Ag and Si in order to form the Ag∕Si SP mode are determined as well, and they turn out to be 500 and 130nm for couplings through air and a SiO2 layer, respectively.

Dispersion relation of Al∕Si surface plasmon in hexagonally ordered aluminum hole arrays

This investigation examines the extraordinary light transmission through periodic hexagonally ordered aluminum hole arrays on silicon substrates. The holes are circular and the arrays with various hole diameters were fabricated. The transmission spectra through the hole arrays were measured as a function of the incident angle of the light beam. It is observed that the transmission peak splits into two when the diameter of the hole is close to half of the lattice constant. At larger incident angles, the six degenerate (1,0) Al∕Si surface plasmon modes split into four or three modes depending on the symmetry axis, and even higher order modes can be identified for small hole diameters.

Remotely coupled surface plasmons in a two-colored plasmonic thermal emitter

A two-colored plasmonic thermal emitter is fabricated with a multilayer structure, in which the dielectric layers are sandwiched between two Ag films. The top Ag film is perforated periodically with holes in a squared array. The thermal radiation of the dielectric layer resonates between two metal films, and surface plasmon polaritons are induced on the top Ag film and then converted to light radiation. Furthermore, if the single dielectric layer is replaced with double layers, then an emission peak that corresponds to the remotely coupled surface plasmon is found in the plasmonic thermal emitter, and the coupling length is less than 500nm.