Wen-Hao Cho

Residual stress in obliquely deposited MgF2 thin films.

MgF(2) films with a columnar microstructure are obliquely deposited on glass substrates by resistive heating evaporation. The columnar angles of the films increases with the deposition angle. Anisotropic stress does not develop in the films with tilted columns. The residual stresses in the films depend on the deposition and columnar angles in a columnar microstructure.

Head-up display using an inclined Al2O3 column array

An orderly inclined Al2O3 column array was fabricated by atomic layer deposition and sequential electron beam evaporation using a hollow nanosphere template. The transmittance spectra at various angles of incidence were obtained through the use of a Perkin-Elmer Lambda 900 UV/VIS/NIR spectrometer. The inclined column array could display the image information through a scattering mechanism and was transparent at high viewing angles along the deposition plane. This characteristic of the inclined column array gives it potential for applications in head-up displays in the automotive industry.

Microstructure and optical properties of Al 2 O 3 prepared by oblique deposition using microsphere shell templates

We fabricated an orderly inclined Al2O3 column array using a hollow microsphere template. The microstructure and optical properties were investigated with scanning electron micrography and a UV/VIS spectrometer, respectively. Microsphere shell templates were formed using atomic layer deposition to prevent the melting of polystyrene microspheres during the following high-temperature deposition process. An inclined Al2O3 column array with a 30° tilt angle was grown by oblique deposition on a substrate with a 75.5° tilt angle with respect to the substrate normal. Birefringence and photonic crystalline behavior can be observed in the orderly inclined column array. The difference in the refractive indices between the p and s polarizations of the orderly inclined Al2O3 column array was about 0.1. The photonic properties of the crystal were enhanced compared to those of substrates without patterns.

Investigation on optical and electrical properties of ZnO sandwich structure with metal interlayer

The dielectric–metal–dielectric (DMD) sandwich structure is fabricated by the RF magnetron sputtering. The effects of sputtering voltage, thickness of the metal layer, and process temperatures on the optical, crystalline structure, and electrical properties of the zinc oxide (ZnO) films were investigated by UV–vis spectrometry, X-ray diffraction and electron energy loss spectroscopy (EELS). Silver, copper and aluminum are used for the DMD sandwich metal layer in this research. The thickness of the dielectric films is decided by admittance loci analysis base on the selected metal characteristic. The optical average transmittance in the visible spectrum and bulk resistivity of the DMD with intermediate Ag layer can reach 85% and 3 × 10−5 Ω cm, respectively.

Controllable photonic mirror fabricated by the atomic layer deposition on the nanosphere template

In this study, a controllable photonic mirror was fabricated using the atomic layer deposition (ALD) coating technique on a polystyrene (PS) nanosphere template. PS nanospheres were self-assembled on an Al/glass substrate to form the bottom electrode. A 20 nm ALD Al2O3 film was then coated onto the surface of the reduced PS nanosphere structure. The PS nanospheres were removed in air at 350°C to form hollow Al2O3 nanospheres. Then a 30 nm indium tin oxide film was sputtered on the hollow nanosphere structure to form the top electrode. The results show that the incorporation of the photonic mirror could control the reflectance to a value of 0.3% per 0.1 V of bias voltage.

The research of oblique deposition of lanthanum fluoride thin films at 193nm

Oblique deposition of lanthanum fluoride thin films was prepared by thermal resistance evaporation. The characteristics (including microstructure, coefficient of tangent rule, birefringence at 193nm and stress) of lanthanum fluoride thin films of have been investigated. The deposition angles increased from 20 to 70 degree, the coefficient of tangent rule decreased from 0.7 to 0.37. When the deposition angles larger than 60 degree, the coefficient held a constant, 0.37. The refractive index at 193nm of oblique deposition films decreased with the deposition angles was larger than 40 degree. The residual stress of films achieved the minimum value at 20-degree deposition angle.

Investigation of the Microstructure, Porosity, Adhesion, and Optical Properties of a WO 3 Film Fabricated Using an E-Beam System With Ion Beam-Assisted Deposition

The relationship between the oxygen pressure, porosity, adhesion, and ion beam-assisted deposition (IAD) conditions for WO₃ electrochromic films prepared using an electron-beam (E-beam) system was investigated. The adhesion of thin films on the substrate by sole E-beam system is very weak. The best method is proposed to obtain good adhesion and better porosity by combining the E-beam evaporation, and the microstructure and coloration efficiency were determined using a field emission scanning electron microscope (SEM) and a spectrometer, respectively. Notably, the effect of the oxygen pressure on the coloration efficiency and porosity of Ta₂O₅/WO₃ films was found to be different. The optimal average transmittance of the electrochromic film in the bleached state was 11%, and in the colored state was 68%, when a Ta₂O₅ thin film was deposited in oxygen at a pressure at 9 × 10^-4 torr using IAD, and a WO₃ thin film was deposited at an oxygen pressure of 7.5 × 10^-5 torr. The studied results are useful for the design of more efficient photoelectrochemical devices employing evaporated WO₃ films.

Preparation of Aluminum Oxide-Coated Glass Slides for Glycan Microarrays

In this study, we report the fabrication of aluminum oxide-coated glass (ACG) slides for the preparation of glycan microarrays. Pure aluminum (Al, 300 nm) was coated on glass slides via electron-beam vapor deposition polymerization (VDP), followed by anodization to form a thin layer (50–65 nm) of aluminum oxide (Al-oxide) on the surface. The ACG slides prepared this way provide a smooth surface for arraying sugars covalently via phosphonate formation with controlled density and spatial distance. To evaluate this array system, a mannose derivative of α-5-pentylphosphonic acid was used as a model for the optimization of covalent arraying based on the fluorescence response of the surface mannose interacting with concanavalin A (ConA) tagged with the fluorescence probe A488. The ACG slide was characterized using scanning electron microscopy, atomic force microscopy (AFM), and ellipsometry, and the sugar loading capacity, uniformity, and structural conformation were also characterized using AFM, a GenePix scanner, and a confocal microscope. This study has demonstrated that the glycan array prepared from the ACG slide is more homogeneous with better spatial control compared with the commonly used glycan array prepared from the N-hydroxysuccinimide-activated glass slide.

Novel structure of controllable of photonic mirror fabricated by atomic layer deposition onnanosphere template

A novel photonic mirror has been fabricated by atomic layer deposition on a polystyrene nanosphere template which controls the reflectance with a tiny value of 0.003% per 0.1V of bias treatment.

A Novel Head-Up Display Using Inclined Al2O3 Column Array

An orderly inclined Al2O3 column array was fabricated by the atomic layer deposition and sequential electron beam evaporation using a hollow nanosphere template. It has potential to apply as HUDs in the automotive industry.