Wen-Hsien Huang

Fabrication and characterization of three-dimensional all metallic photonic crystals for near infrared applications

Three-dimensional all metallic photonic crystals with a feature size of 0.20 μm were fabricated using electron-beam lithography with the photoresist of hydrogen silesquioxane. This process method has high compatibility with the fabrication of damascene copper interconnections and also simplifies the whole process flow. The dependence of the complete photonic band gaps on polarization was experimentally observed and compared with the simulation results. The band edge for the four-layer lattice was found at a wavelength of around 0.80 μm in normal incidence.

Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and AsxSe1−x

In this study, we fabricated a-Se based photosensors with an alternating multilayer structure of a-Se and AsxSe1−x by rotational thermal evaporation deposition. During the deposition of the amorphous AsxSe1−x layers, As diffuses into the underlying a-Se component layers, thereby improving the thermal stability of the multilayer photosensor and thus increasing the breakdown electric field. Although the As doping introduces carrier traps in the a-Se layers, the multilayer photosensors demonstrate an effective quantum efficiency comparable to the single-layered a-Se sensor under the blue light illumination but are with a lower dark current density by two orders of magnitude. In addition to the top AsxSe1−x layer being functioning as an electron blocking layer, carrier traps present in the multilayer structure may decrease the drift mobility of charge carriers and disturb electric field distribution in the photosensors, thereby suppressing the dark current.

Fabrication and Application of Copper Sub-Microdoughnut with Electroplating Method on Patterned Nickel Template

The sub-microdoughnut-like copper periodic structure is fabricated by an electroplating method on a patterned Ni template. The diameter of the cover Cu doughnut hole can be controlled by plating duration. This structure can be applied in a biosensor due to surface plasmonic resonance, and for a novel optical device with a variable hole diameter and period of that array. The magnetic force microscope was used for evaluating the biosensing response under the addition of magnetic proteins (metallothionein, Mn 2 Cd 5 metallothionein, and ferritin) on that sample before and after magnetization. In addition, the optical properties before and after magnetization were measured and scanned by Fourier transform IR spectroscopy. Some interesting behaviors were observed in the spectra and transmitting ratio under different polarization incident conditions.

Thermal emission at near-infrared wavelengths from three-dimensional copper photonic crystals

A three-dimensional copper photonic crystal was fabricated with the high compatibility process, damascene copper interconnections technique. The reflectance and transmittance spectra of this structure were measured with the Fourier-transform infrared spectroscopy and simulated with the 3 D finite-difference time-domain method. From the experiment data, it is shown that this structure exhibits a large photonic bandgap from mid-infrared regime to λ = 1.95 μm. At a heating temperature of 420 °C, it is observed that thermal emission is enhanced near the bandedge λ = 1.71 μm and suppressed in the bandgap region. This is attributed to the enhancement of photonic density of states near the bandedge.

Fabrication and properties of Cu–Ni mixed-metal periodical array for midinfrared filtering and hydrophobic application

Cu was grown successfully on Ni film as a conductive layer that demonstrated a stronger Cu (111) preferred crystallographic orientation. Furthermore, we studied the scale effect of various periods of patterned Ni lines separated by variable widths of SiO2. When Cu was electroplated onto this patterned Ni, it preferentially deposited on the Ni edges adjacent to the SiO2 stripes, resulting in a Cu–Ni–Cu–SiO2, Cu–SiO2–Cu, or Cu–Cu structure, depending on the dimensions of the starting Ni pattern and the deposition time. There are two reflective dips at 2.2 and 8μm wavelengths using Fourier transform infrared spectroscopy, which revealed a trend of narrower bandwidth in reflective spectra and a redshift effect with increasing deposition time. Interestingly, a hydrophobic surface was also observed due to its particular surface-roughness structures that could be controlled by the deposition time and altered the contact angle from 72° to 110° without coating any extra low free-energy materials.