Dongin Lee

Sensing behavior of the polypyrrole and polyaniline sensor for several volatile organic compounds

The sensing characteristics of conducting polymers to several volatile organic compounds were investigated with a UV-Vis-NIR spectrophotometer, dynamic contact angles measurement and scanning probe microscopy (SPM). When gases were absorbed, the polypyrrole (PPy) and polyaniline (PANi) exhibited positive and negative sensitivity, respectively. The PPy-based sensor demonstrated decreasing conductivity while the PANi sensor exhibited increasing conductivity when the polarity of the molecules absorbed increased. PPy film has an hydrophilic property while the PANi film a hydrophobic one. These changes in polymer conductivity, it is speculated, are due to the interruption of free carrier movement or the generation of polarons by the absorbed molecules.

The effect of a migration barrier between tungsten oxide and indium tin oxide thin films in electrochromic devices

Abstract Electrochromic devices are based on the reversible insertion of guest atoms into the structure of the host solid. However, after cyclic operation, the tungsten in a WO 3 film and the indium in an ITO (indium tin oxide) film were migrated with each other and the electrochromic property of the device was decreased. The trapped lithium is associated with the indium (diffuse out from ITO to WO 3 film). In order to block migration, a thin tungsten barrier film was deposited on the ITO film. With the tungsten barrier, the indium and tungsten migration was effectively blocked and the decrease of the maximum current of cyclic voltammogram was reduced to 1/10. We can now manufacture electrochromic devices that have long lifetimes and high transmittance variance.

Fabrication of Probe Beam by Using Joule Heating and Fusing

Abstract In this paper, we developed a beam of MEMS probe card using a BeCu sheet. Silicon wafer thickness of 400 m was fabricated byusing deep reactive ion etching (RIE) process. After forming through silicon via (TSV), the silicon wafer was bonded with BeCu sheet bysoldering process. We made BeCu beam stress-free owing to removing internal stress by using joule heating. BeCu beam was fused byusing joule heating caused by high current. The fabricated BeCu beam measured length of 1.75 mm and width of 0.44 mm, and thicknessof 15 m. We measured fusing current as a function of the cutting planes. Maximum current was 5.98 A at cutting plane of 150 m 2 . Theproposed low-cost and simple fabrication process is applicable for producing MEMS probe beam. Keywords : BeCu, Fusing, Joule heating, Probe card 1234+ Corresponding author: chocs@knu.ac.kr(Received : Dec. 6, 2012, Revised : Jan. 21, 2013, Accepted : Jan. 21, 2013)This is an Open Access article distributed under the terms of the Creative CommonsAttribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0)which permits unrestricted non-commercial use, distribution, andreproduction in any medium, provided the original work is properly cited.

Visible optical sensing of ammonia based polyaniline film

Optical sensors have been used in new technologies for detecting small amounts of chemical, gaseous species. In this work, a new optical gas sensor using thin polymer layers was developed. We selected a polymer for the gas sensing material. Polymers were synthesized and chemically polymerized by using distilled aniline. The optical property of the polymer as a sensing material was analyzed by using UV-Vis-NIR. These layers were prepared by using centrifugal force. The polymer layer was uniformly deposited on an inner glass pillar The light source was a red-LED with 655 nm wavelength. The light power transmitted through the guide cell was measured with a photodiode. The variation of light power transmitted was detected when the gas was absorbed in the polymer layer The transmitted light intensity was decreased because gas molecules were absorbed into the polymer layer. NH/sub 3/ gas is used as the evaluating gas. This optical sensor showed a good sensitivity to NH/sub 3/ gas.

Fabrication of BeCu module probe array using heating and fusing currents

We have developed a novel probe array using BeCu sheets, to solve the high-production-cost problem associated with conventional MEMS probe cards. The BeCu probe has a simple structure and offers several advantages such as ease of fabrication and rapid prototyping; further, the fabrication process is cost-effective. The proposed array was fabricated by applying a suitable heating current (for plastic deformation via Joule heating) and fusing current (for cutting the array) to a BeCu beam. The stress relaxation time was 7 min during the application of a heating current of 4 A, and the fusing current was 20 A. The fabricated probe array is suitable for use in various complicated semiconductor chip tests.

Fabrication of Thick Silicon Dioxide Air-Bridge and Coplanar Waveguide for RF Application Using Complex Oxidation Process and MEMS Technology

This paper proposes a thick oxide air-bridge structure which can be used as a substrate for RF circuits. The structure was fabricated by anodic reaction, complex oxidation and micromachining technology using TMAH etching. High quality films were obtained by combining low temperature thermal oxidation (, 1 hr at ) and rapid thermal oxidation (RTO) process (, 2 min). This structure is mechanically stable because of thick oxide layer up to and is expected to solve the problem of high dielectric loss of silicon substrate in RF region. The properties of the transmission line formed on the oxidized porous silicon (OPS) air-bridge were investigated and compared with those of the transmission line formed on the OPS layers. The insertion loss of coplanar waveguide (CPW) on OPS air-bridge was (about 2dB) lower than that of CPW on OPS layers. Also, the return loss of CPW on OPS air-bridge was less than about -20 dB at measured frequency region for 2.2 mm. Therefore, this technology is very promising for extending the use of CMOS circuitry to higher RF frequencies.