A low-cost CMOS programmable temperature

A novel uncalibrated CMOS programmable temperature switch with high temperature accuracy is presented. Its threshold temperature T-th can be programmed by adjusting the ratios of width and length of the transistors. The operating principles of the temperature switch circuit is theoretically explained. A floating gate neural MOS circuit is designed to compensate automatically the threshold temperature T-th variation that results form the process tolerance. The switch circuit is implemented in a standard 0.35 mu m CMOS process. The temperature switch can be programmed to perform the switch operation at 16 different threshold temperature T(th)s from 45-120 degrees C with a 5 degrees C increment. The measurement shows a good consistency in the threshold temperatures. The chip core area is 0.04 mm(2) and power consumption is 3.1 mu A at 3.3V power supply. The advantages of the temperature switch are low power consumption, the programmable threshold temperature and the controllable hysteresis.

Demonstration of low-cost Si-based tunable long-wavelength resonant-cavity-enhanced photodetectors

A simple process for fabricating low-cost Si-based continuously tunable long-wavelength resonant-cavity-enhanced (RCE) photodetectors has been investigated. High-contrast SiO2/Si(Deltan similar to2) was employed as mirrors to eliminate the need to grow thick epitaxial distributed Bragg reflectors. Such high-reflectivity SiO2/Si mirrors were deposited on the as-grown InGaAs epitaxy layers, and then were bonded to silicon substrates at a low temperature of 350 C without any special treatment on bonding surfaces, employing silicate gel as the bonding medium. The cost is thus decreased. A thermally tunable Si-based InGaAs RCE photodetector operating at 1.3-1.6 mum was obtained, with a quantum efficiency of about 44% at the resonant wavelength of 1476 nm and a tuning range of 14.5 nm. It demonstrates a great potential for industry processes. (C) 2005 American Institute of Physics.

High-efficiency and low-cost hybrid nanomaterial as enhancing electrocatalyst: Spongelike AWN core/shell nanomaterial with hollow cavity

A high-efficiency and low-cost spongelike Au/Pt core/shell electrocatalyst with hollow cavity has been facilely obtained via a simple two-step wet chemical process. Hollow gold nanospheres were first synthesized via a modified galvanic replacement reaction between Co nanoparticles in situ produced and HAUCl(4). The as-prepared gold hollow spheres were employed as seeds to further grow spongelike Pt shell. It is found that the surface of this hybrid nanomaterial owns many Pt nanospikes, which form a spongelike nanostructure. All experimental data including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-vis-near-infrared spectroscopy have been employed to characterize the obtained Au/Pt hybrid nanomaterial. The rapid development of fuel cell has inspired us to investigate the electrocatalytic properties for dioxygen and methanol of this novel hybrid nanomaterial. Spongelike hybrid nanomaterial mentioned here exhibits much higher catalytic activity for dioxygen reduction and methanol oxidation than the common Pt electrode.

Fabrication of low-cost and high-reflectivity bottom mirrors for Si-based micro-cavity devices

A novel and simple way to prepare high-reflectivity bottom mirrors for Si-based micro-cavity devices is reported. The bottom mirror was deposited in the hole, which was etched from the backside of the sample by ethylenediamine-pyrocatechol-water solution with the buried Sio, layer in the silicon-on-insulator substrate as the etching-stop layer. The high-reflectivity of the bottom mirror deposited in the hole and the narrow hill width at half maximum of the cavity formed by this method both indicate the successful preparation of the bottom mirror for Si-based micro-cavity devices.

The improvement of thick oxidized porous silicon layer growth process - art. no. 60290S

Oxidizing thick porous silicon layer into silicon dioxide is a timesaving and low-cost process for producing thick silicon dioxide layer used in silicon-based optical waveguide devices. The solution of H2O2 is proposed to post-treat thick porous silicon (PS) films. The prepared PS layer as the cathode is applied about 10 mA/cm(2) current in mixture of ethanol, HF, and H2O2 solutions, in order to improve the stability and the smoothness of the surface. With the low-temperature dry-O-2 pre-oxidizations and high-temperature wet O-2 oxidizations process, a high-quality SiO2 30 mu m thickness layer that fit for the optical waveguide device was prepared. The SEM images show significant improved smoothness on the surface of oxidized PS thick films, the SiO2 film has a stable and uniformity reflex index that measured by the prism coupler, the uniformity of the reflex index in different place of the wafer is about 0.0003.

Fabrication of low cost Si-based tunable high performance resonant cavity enhanced photodetectors

Low cost Si-based tunable InGaAs RCE photodetectors operating at 1.3similar to1.6 mum were fabricated using sol-gel bonding. A tuning range of 14.5 nm, a quantum efficiency of 44% at 1476 nm and a 3-dB bandwidth of 1.8 GHz were obtained.

A simple and low-cost airlift photobioreactor for microalgal mass culture

A simple, low-cost, and efficient airlift photobioreactor for microalgal mass culture was designed and developed. The reactor was made of Plexiglas, and composed of three major parts: outer tube, draft tube and air duct. The fluid-dynamic characteristics of the airlift reactor were studied. The system proved to be well suited to the mass cultivation of a marine microalga, Chlorella sp. In batch culture, the biomass volumetric output rate of 0.21 g l(-1) d(-1) was obtained at the superficial gas velocity of 4 mm s(-1) in the draft tube.

Low threshold current density, low resistance oxide-confined VCSEL fabricated by a dielectric-free approach

We present the fabrication process and experimental results of 850-nm oxide-confined vertical cavity surface emitting lasers (VCSELs) fabricated by using dielectric-free approach. The threshold current of 0.4 mA, which corresponds to the threshold current density of 0.5 kA/cm(2), differential resistance of 76 Omega, and maximum output power of more than 5 mW are achieved for the dielectric-free VCSEL with a square oxide aperture size of 9 mu m at room temperature (RT). L-I-V characteristics of the dielectric-free VCSEL are compared with those of conventional VCSEL with the similar aperture size, which indicates the way to realize low-cost, low-power consumption VCSELs with extremely simple process. Preliminary study of the temperature-dependent L-I characteristics and modulation response of the dielectric-free VCSEL are also presented.

A novel process for converting coalmine-drained methane gas to syngas over nickel-magnesia solid solution catalysts

A novel process is developed in this paper for utilizing the coalmine-drained methane gas that is usually vented straight into the atmosphere in most coalmines worldwide. It is expected that low-cost syngas can be produced by the combined air partial oxidation and CO2 reforming of methane, because this process utilizes directly the methane, air, and carbon dioxide in the coalmine-drained gas without going through the separation step. For this purpose, a nickel-magnesia solid solution catalyst was prepared and its catalytic performance for the proposed process was investigated. It was found that calcination temperature has significant influence on the catalytic performance due to the different extent of solid solution formation in the catalysts. A uniform nickel-magnesia solid solution catalyst exhibits higher stability than the catalysts in which NiO has not completely formed solid solution with MgO. Its catalytic activity and selectivity remain stable during 120 h of reaction. The product H-2/CO ratio is mainly dependent on the feed gas composition. By changing CO2/air ratio of the feed gases, syngas with a H-2/CO ratio between 1 and 1.9 can be obtained. The influences of reaction temperature and nickel loading on the catalytic performance were also investigated. (c) 2004 Elsevier B.V All rights reserved.

高精度微结构聚合物光栅的复制技术

光栅复制是降低光栅制造成本,提高产量的一条有效途径。研究了利用紫外压印技术复制微结构光栅的方法。使用玻璃基底矩形浮雕结构的微结构光栅作为母光栅,给出了利用聚二甲基硅氧烷(PDMS)制作光栅模具和在光敏聚合物材料上复制微结构光栅的详细过程。经过优化工艺条件,成功地复制了一系列不同周期和开口比的微结构光栅,测试了复制光栅和母光栅的衍射图像和0级与±1级的衍射强度,结果表明,复制光栅和母光栅的衍射图像与光强分布基本一致。

Synthesis and luminescence of ZnMgS : Mn2+ nanoparticles

Efficient green emission from ZnMgS:Mn2+ nanoparticles prepared by co-doping Mg2+ and Mn2+ ions into ZnS lattices has been observed. The synthesis is carried out in aqueous solution, followed by a post-annealing process, thus showing the features of less complexity, low cost, and easy incorporation of dopants. In comparison with the emission of ZnS:Mn2+ nanoparticles, which is located generally around 590 nm, the photoluminescence of ZnMgS:Mn2+ nanoparticles is blue-shifted by 14 nm in wavelength, leading to the enhanced green emission. The X-ray diffraction, electron spin resonance, and pressure dependent photoluminescence measurements suggest that the change of the crystal field caused by Mg2+ ionic doping and the lower symmetry in the nanoparticles may account for the blue-shift of the photoluminescence. The ZnMgS:Mn2+ nanoparticles with 1% Mn2+ doping exhibit the strongest luminescence, which could potentially meet the requirements for the construction of green light emitting diodes.

Solid-phase crystallization and dopant activation of amorphous silicon films by pulsed rapid thermal annealing

An improved pulsed rapid thermal annealing method has been used to crystallize amorphous silicon films prepared by PECVD. The solid-phase crystallization and dopant activation process can be completed with time-temperature budgets such as 10 cycles of 60-s 550 degrees C thermal bias/l-s 850 degrees C thermal pulse. A mean grain size more than 1000 Angstrom and a Hall mobility of 24.9 cm(2)/V s are obtained in the crystallized films. The results indicate that this annealing method possesses the potential for fabricating large-area and good-quality polycrystalline silicon films on low-cost glass substrate. (C) 1998 Elsevier Science B.V. All rights reserved.

Low Temperature Deposited Nano-structured Vanadium Oxide Thin Films for Uncooled Infrared Detectors

A novel process of room temperature ion beam sputtering deposition of vanadium oxide films and low temperature post annealing for uncooled infrared detectors was proposed in this work. VOx thin films with relatively low square resistance (70 K Omega / square) and large temperature coefficient of resistance (more than 3%/K) at room temperature were fabricated using this low temperature process which was very compatible with the process of uncooled infrared detectors based on micromachined technology. Furthermore, chemical composition and film surface have been characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results showed that the main composition of the processed thin films was V2O5 and the thin films were in the process of crystallization.