In this paper, we report on how electrochromic coloration is affected by oxygen deficient stoichiometries in amorphous tungsten oxide (a-WOx) films prepared by a dc reactive magnetron sputtering. The peak color efficient (CE) value of oxygen partial pressure at the optimum 6.5×10-3 Torr is improved about nine-fold larger than that of 2.0×10-3 Torr even in the nearly stoichiometric a-WOx films. We attributed that the optical absorption of a colored a-WOx film can be satisfactorily described by an intervalence charge-transfer transition (ICTT) mechanism between localized W5+ and W6+ states. Therefore, we have determined the most suitable condition (by increasing the partial oxygen pressure) to produce a-WOx films, thus offering a good electrochromic performance for opto-switching 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 OEIC's applications.
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.
A prototype contact type micro piezoresistive shear-stress sensor that can be utilized to measure the shear stress between skin of stump and socket of Above-Knee (AK) prosthesis was designed, fabricated and tested. Micro-electro-mechanical system (MEMS) technology has been chosen for the design because of the low cost, small size and adaptability to this application. In this paper, the Finite Element Method (FEM) package ANSYS has been employed for the stress analysis of the micro shear-stress sensors. The sensors contain two X-ducers that will transform the stresses into an output voltage. In the developed sensor, a 3000X3000X3000 micrometers (superscript 3/ square membrane is formed by bulk micromachining of an n-type <100> monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 10(superscript 15/ atoms/cm(superscript 2/. Static characteristics of the shear sensor were determined through a series of calibration tests. The fabricated sensor exhibits a sensitivity of 0.13mV/mA-Mpa for a 1.4N full scales shear force range and the overall mean hysteresis error is than 3.5%. In addition, the results simulated by FEM are validated by comparison with experimental investigations.
In this paper, a new electro-chromic device (ECD) is developed by tungsten oxide (WO3) thin film integrated with a-Si1-xGex:H pin photodetector. With the addition of the palladium (Pd) film to ionize hydrogen gas, the WO3 thin film will react with hydrogen ion and transfer from transparency to blue color. This color change will degrade the absorption of light with wavelength larger than blue color. First, we determine the most suitable condition (by increasing the partial oxygen pressure) to produce a-WOx films, thus offering a good electro- chromic performance for opto-switching applications. Then, the photo current generated by a-Si1-xGex:H pin photodetector will be lowered down, thus detecting the existing of hydrogen gas. Especially, the WO3-pin hydrogen sensor also shows highly selectivity with hydrogen gas to separate from CO and C2H5OH gases.
In this paper, different structures of high-speed infrared (IR) sensors based on amorphous silicon germanium and amorphous silicon hetero-structures have been successfully developed on crystalline silicon substrates. Experimental results of these developed structures exhibit a superior device performance to that of a traditional pin amorphous photo-sensor prepared on a glass substrate, especially significant improvements in the rise time from 465 (microsecond(s) ) to 195 (microsecond(s) ), and the dark current from 50 ((mu) A) to 3.3 ((mu) A) for 5 (V) reverse bias.
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.
An IR sensor with the lead-titanate (PbTiO3) thin-film and thermal isolation improvement structure using the technology of micro-opto-mechanical system has been designed, fabricated and developed. In this paper, both numerical analysis of the static operation mechanisms such as the effects of IR light power on the depletion layer width and voltage drop across the thin PbTiO3 film, and the dynamic responses of a thin-film pyroelectric sensor to sinusoidal modulated radiation are reported and compared to the experimental results. The fitting is quite well. The major IR-sensing par ton the cantilever beam of the developed sensor consists of a 50-nm PbTiO3 layer deposited by RF sputtering, and a gold layer evaporated as an IR radiation absorber. With active cantilever dimensions of 200 X 100 X 5 micrometers 3 formed by etching processes, the cantilever structure exhibits a much superior performances to that of a traditional IR-sensing bulk structure under the 800-(mu) W incident optical light with wavelength of 970 nm.
An IR sensor with the lead-titanate thin-film using the technology of micro-electro-mechanical systems to achieve a better thermal isolation structure has been fabricated and developed. The major IR-sensing part on the cantilever beam with dimensions of 200 X 100 X 2 micrometers 3 consists of a 500-angstrom lead-titanate layer deposited by RF sputtering, and an evaporated bismuth layer. This thermal isolation improved structure exhibits a much superior performance to that of a traditional IR-sensing bulk structure on the experimental results, which show a 200 percent and 300 percent improvement in current gain under the incident optical power 500 (mu) W and 6V applied bias at room temperature and 77 degrees K, respectively.
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