Jing-Yu Chen

Effect of Crystallinity on the Optical Reflectance of Cylindrical Colloidal Crystals

We fabricate cylindrical colloidal crystals (CCCs) via electrophoretic depositions of polystyrene microspheres on a carbon fiber in a concentric arrangement. Images from optical and scanning electron microscope indicate that the CCCs of 460 nm microspheres reveal a semicrystalline structure in close-packed lattice, while the CCCs of 660 exhibit an amorphous arrangement. In optical reflectance spectra, both CCCs demonstrate a dispersive photonic bandgap as compared to that from planar counterparts. The curved contour for the CCCs renders incident light interacting with reflecting planes at slightly different angles, leading to a notable reduction in the reflectance intensity and minor relocation of photonic bandgap contingent on their crystallinity.

Electrical properties of InSb metal/insulator/semiconductor diodes prepared by photochemical vapour deposition

Abstract Thin SiO 2 films were prepared by photochemical vapour deposition. IR absorption and Auger electron spectroscopy showed that the dominant components of the oxide are silicon and oxygen with a small amount of hydrogen. Metal/insulator/semiconductor (MIS) capacitors were constructed on InSb substrates. Capacitance-voltage characteristics of the MIS capacitors were measured, and a midgap interface state density of the order of 10 12 cm -2 eV -1 was determined. The amount of hysteresis observed was found to be about 10% of the inversion bias voltage. Annealing studies were also conducted to improve the electrical properties. After annealing, the midgap interface state density was reduced to 5 × 10 11 cm -2 eV -1 and the amount of hysteresis reduced to 5% of the inversion bias voltage.

Galvanostatic electrodeposition of SnCu 2–4 Ni 1–2 as a lead-free solder

SnCu2–4Ni1–2 as a lead-free solder was prepared from both sulfate and chloride plating solutions by galvanostatic electrodeposition. Current-potential polarizations for both plating baths were obtained with their respective deposition rates measured. Characterizations including SEM, EDX, and XRD were carried out to obtain relevant materials properties.

Electroplating of Sn-2.5Ag solders as 20 μm pitch micro-bumps

A Cu/Ni UBM and Sn-2.5Ag lead-free solder for 20 μm pitch micro-bump was successfully fabricated via consecutive electroplatings of Cu, Ni, and binary SnAg. Materials characterizations such as Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Electron Probe Micro-analyzer (EPMA), and X-ay Photoelectron Spectroscopy (XPS) were carried out to obtain relevant materials properties. We observed a strong effect of the plating current density on the resulting bump morphologies. After reflow, the solder revealed a spherical shape with a composition variation within 0.2 wt%.