Jyh-Jier Ho

Novel nitrogen monoxides (NO) gas sensors integrated with tungsten trioxide (WO3)/pin structure for room temperature operation

Abstract A new electrochromic device is developed by tungsten trioxide (WO 3 ) thin film integrated with a-Si 1− X Ge X :H pin photodetector. With the addition of the gold (Au) film to ionize nitrogen monoxide (NO) gas, the WO 3 thin film will react with ion and transfer from transparency to blue color. This color change will degrade the absorption of light with wavelength larger than blue color. Therefore, the photocurrent generated by a-Si 1− X Ge X :H pin photodetector will be lowered down, thus detecting the existing of NO gas. In the case of 150-ppm NO gas and 300 K operation, the induced photocurrent, the response and recovery times for the sensitivity are about 0.5 mA, 10 s, and 2 min, respectively. Especially, the WO 3 -pin NO sensor also shows highly selectivity with NO gas to separate from CO and C 2 H 5 OH gases.

Optimizing indium tin oxide thin films with bipolar d.c.-pulsed magnetron sputtering for electrochromic device applications

In this paper, indium tin oxide (ITO) films were prepared by bipolar d.c.-pulsed magnetron sputtering in a mixture of argon and oxygen onto unheated glass substrates. A target of ITO with 10 weight percent (wt %) tin was used. The influences of ratios of t−on/t+on (negative pulse-on time/positive pulse-on time) on the optical, electrical, and structural properties of ITO films have been investigated. The correlations between the deposition parameters and the film properties were discussed. An optimal condition based on reactive bipolar d.c.-pulsed sputtering for obtaining high transmittance, low resistivity, and low surface roughness of ITO films with high deposition rate is suggested. Then, ITO films grown at room temperature by bipolar d.c.-pulsed sputtering were used to form electrochromic devices of WO3. Better electrochromic performances were found in comparison to those measured with commercially available ITO films on glass substrates.

Dramatic improving luminous efficiency of organic light emitting diodes under low driving current using nitrogen doped hole transporter

Abstract In this letter, output luminance, current efficiency and power efficiency of the organic light emitting diodes (OLEDs) with N 2 doped hole transport layer (HTL) have been studied in detail. Experimental results show that the current efficiency and the power efficiency thus in turn the output luminance of OLEDs prepared with HTL evaporated in the optimum N 2 gas ambient pressure of 1×10 −4 Torr are improved about 13, 9 and 12 times, respectively, under 2.7 mA/cm 2 driving current. The significant improving mechanism has been illustrated comprehensively with a series of schematic models.

Improving turn on voltage and driving voltage of organic electroluminescent devices with nitrogen doped electron transporter

Abstract In this letter, I/V curves, output luminance of the organic light emitting diodes (OLEDs) with N2 doped electron transport layer (ETL) have been studied in detail. Experimental results show that the turn on voltage and driving voltage of OLEDs with ETL evaporated in the optimum N2 gas ambient pressure of 1×10−4 Torr are reduced from 3.5 to 1 V and 7.7 to 5.7 V, respectively. The significant improving mechanism has been illustrated comprehensively with a schematic energy diagram model.

Cubic Single-Crystalline Si1 − x − y C x N y Films with Mirror Face Prepared by RTCVD

© The Electrochemical Society, Inc. [2001]. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS). The archival version of this work was published in [Electrochemical and Solid-State Letters, Vol.4, No.11, pp.G91-G93].”

Design and fabrication of a novel crystal SiGeC far infrared sensor with wavelength 8-14 micrometer

In this paper, we report the design, fabrication, and performance of a novel crystal SiGeC infrared sensor with wavelength 8-14 /spl mu/m by bulk micromachining technology for portable far infrared ray (FIR) in rehabilitation system application. The working principle of the sensor is based on the change of thermistors resistance under the irradiation FIR light. The thermistor in the IR detector is made of Si/sub 0.68/Ge/sub 0.31/C/sub 0.01/ thin films for its large activation energy of 0.21 ev and the temperature coefficient (TCR) of -2.74%, respectively. Finite element method package ANSYS has been employed for analyze of the thermal isolation and stress distribution in the IR detector. The dimension of the microbridge fabricated by anisotropic wet etching is 2000 /spl times/ 2000 /spl times/ 25 /spl mu/m/sup 3/. The developed FIR sensor exhibits the thermal conductance of 1.85 /spl times/ 10/sup -1/ WK/sup -1/ and the heat capacity as 7.4 /spl times/ 10/sup -7/ JK/sup -1/ under air ambient at room temperature. The responsivity is 523 VW/sup -1/ in the waveband 8-14 /spl mu/m with nickel absorber under a bias voltage 1.5 V.

Performance analysis of an infrared sensor (metal/ferroelectric/semiconductor) with high-speed response

In this paper, a thin PbTiO3-n-p+ silicon switch sensor has been developed, in which the switching voltage (the turned-on voltage) changes in proportion to the infrared light power. The sensor has a rapid response time of 0.65 μs compared with other conventional infrared sensors. It is attributed to the rapid switching device structure and the smaller pyroelectric layer thickness, 50 nm. Meanwhile in this paper, we have successfully analyzed the rapid switching transient response by using heat conduction and switching theory. The experimental results are in agreement with the theoretical analysis.

Performance analysis of an integrated pin/MISS OEIC for high-current photosensing applications

In this paper, a new pin/MISS photoreceiver with very high output current has been developed successfully by using the combination of the amorphous silicon germanium alloy pin photodiode and metal insulator semiconductor switch (MISS) device. The developed photoreceiver uses the pin photodiode as the light absorption structure and light wavelength selector and the MISS device as the photocurrent amplifier. Based on the experimental results, the photoreceiver yields a very high output current of 3.2 mA at a voltage bias of 6V under an incident light power Pin equals 100 μW and has a rise time of 465 μs at a load resistance R equals 1 KΩ. The peak response wavelength of the diode is at 905 nm, i.e. infrared light. Thus the high output current pin/Miss photoreceiver provides a good candidate for the IR OEICs applications.

Performance analysis and development of high-temperature B-SiC/Si optoelectronic devices with porous silicon substrate

In this paper, to suppress dark current of high temperature (beta) -SiC/Si optoelectronic device with a porous substrate has been studied. A pin structure was used to demonstrate the applicability. Experimental results show a twelve-fold improvement in optical gain at 200 degree(s)C operating temperature for the sample prepared on the porous silicon substrate as compared to the sample prepared on the silicon substrate, respectively. The improvement is attributed to the suppression of dark current by the high resistivity and flexibility of the porous substrate. A (beta) -SiC/Si optoelectronic device was fabricated both on porous silicon substrate and conventional silicon substrate, respectively. Experimental results show the optical current ratio can be improved up to 400% at room temperature and 3000% at 200 degree(s)C operating temperature, respectively, with the porous silicon substrate.