共查询到20条相似文献,搜索用时 31 毫秒
1.
MEMS structures for micro gas sensors had advantage for lower power consumption, reducing size, and easily making cavity structures.
Also, co-planar type MEMS structures (CPMS) for gas sensors with low power consumption heater and dispensed sensing materials were newly proposed and
investigated. CPMS, which were formed with micro heater and sensing electrodes at the same layer, to reduce process steps,
diffusions between upper layer and lower layer, and thermal differences between the center and the periphery of the sensing
layer compared with stacked structure. Dispensing method guided by back-side etched well was good for forming sensing material
on sensing electrode and had advantage that various sensing materials could be applied for array type sensors. CPMS were fabricated
on four-inch diameter and double side polished (100) silicon wafers and using anisotropic bulk silicon micromachining for
membrane formation and etched well. A size of chips with 1.15 mm × 1.15 mm membrane was 4.8 mm × 4.8 mm. And co-planar type
sensing electrodes were located in the middle of low stress SiO2/Si3N4 (400 nm /1 μm) membranes. Membranes are thermally isolated from the chip frame because they have low thermal conductivity,
generally. Temperatures were measured using IR thermometer with linearly increasing applied power. Power consumption at 400∘C was 150 mW. Membranes of CPMS were withstood up to 730∘C at the power of 350 mW. Characteristics of micro heaters for various heater widths of 50 μm, 75 μm, 100 μm and ratios of
membrane dimension to heater dimension were measured. Sensing materials guided by micromachined well were dispensed on sensing
electrodes. CPMS were mounted on a TO-8 package. From these results, fabricated and characterized CPMS could be used for applications
in portable gas sensors for detection of CO, NOx, CHx, H2S, and so on. 相似文献
2.
Jae Hong Park Tae Yun Kwon Hyung Joon Kim Seung Rae Kim Dae Sung Yoon Chae-Il Cheon Hwan Kim Tae Song Kim 《Journal of Electroceramics》2006,17(2-4):565-572
The PZT thick film cantilever devices fabricated via MEMS process have much attraction because they are appropriate for biological
transducer or sensor, resulting from their large actuating force and relatively high sensitivity especially in liquid. By
means of resonance behavior, theoretical calculation and experimental verification of the PZT thick film cantilever devices
have not been studied before. Accordingly, we focused on the sensitivity analysis and interpretation of the PZT thick film
cantilevers in this study. Especially, the investigation for mass sensitivity of the PZT thick film cantilever is of importance
for physical, chemical and biological sensing application. The PZT thick film cantilever devices were constructed on Pt/TiO2/SiN
X
/Si substrates using screen printing method and MEMS process. The harmonic oscillation response (resonance frequency) was
measured using an optical laser interferometric vibrometer. The effect of cantilever geometry on the resonance frequency change
was investigated. Compared with the theoretical resonant frequency change by mass loading, the experimental resonant frequency
change of the PZT micromechanical thick film cantilever shows a variation of less than 2%. Mass sensitivities are estimated
to be 30.7, 57.1 and 152.0 pg/Hz for the 400 × 380 μm, 400 × 480 μm and 400 × 580 μm cantilever, respectively. 相似文献
3.
To satisfy demands for detecting chemicals in the environment, versatile sensors are required to detect a rapidly growing
range of chemical species. In this paper, focus is directed on progress being made to develop temperature-independent oxygen
sensors based on the perovskite solid solution system SrTi1−x
Fe
x
O3−δ,and on improving the sensitivity of thin film gas sensors integrated on Si-based self heated substrates. A novel strategy
to produce macroporous films with high surface area for enhanced chemical activity is described, and how this processing strategy
results in markedly improved sensitivity of gas sensors based on a novel material, CaCu3Ti4O12, is demonstrated. 相似文献
4.
Ricardo Rangel Lidia Chávez-Chávez Manuel García-Méndez Eduardo Martínez 《Journal of Electroceramics》2012,28(1):34-44
CeO2, Ce(1-x)MXO2, {M = Ru, In} compounds with sensing properties were fabricated using the sol–gel route. The main purpose was to compare
the efficiency of CeO2 vs. Ce(1-x)MXO2 doped compounds as gas sensors for NO2 detection. Characterization was performed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface
area determination (BET). Measurements of electrical resistance under different conditions of time, concentration and temperature
in the presence of NO2 were carried out. Ruthenium inclusion increased the CeO2 sensor response in a great extent, gas response (S) = 1.8 for CeO2 vs. gas response (S) = 350 for Ce0.95Ru0.05O2 and gas response (S) = 35 for Ce0.95In0.05O2. This behavior is reported by the first time. Our results demonstrate that ruthenium or indium inclusion has been beneficial
for CeO2. Conclusively the materials herein described could be applied as NO2 gas sensors. 相似文献
5.
Yasuhiro Shimizu Nobukuni Nakashima Takeo Hyodo Makoto Egashira 《Journal of Electroceramics》2001,6(3):209-217
NO
x
sensing properties of SnO2-xCr2O3 as a varistor-type gas sensor have been investigated in the temperature range of 200–600°C. The breakdown voltage of SnO2 shifted to a higher electric field upon exposure to NO2 at 300–500°C, and the largest breakdown voltage shift, i.e. the highest NO2 sensitivity was observed at 400°C. In contrast, the direction of the breakdown voltage shift in NO varied with temperature: the breakdown voltage shifted to a lower electric field at 300°C, but to a higher electric field at 500°C, and remained almost unchanged at 400°C. The NO2 sensitivity of SnO2 was superior to the NO sensitivity at every temperature, and then the SnO2 exhibited good selectivity to NO2 at 400°C. The breakdown voltage of Cr2O3 shifted in the reverse direction upon exposure to NO and NO2, in comparison with those observed with SnO2, owing to its p-type semiconductivity. Thus, Cr2O3 also exhibited certain sensitivity to both NO and NO2 at 200°C, being more sensitive to NO2, though the sensitivities decreased drastically at temperatures higher than 300°C. The addition of 5.0 wt% Cr2O3 to SnO2 resulted in a significant improvement of NO and NO2 sensitivities at 600°C, being accompanied by an increase in the breakdown voltage in air. Especially, the NO sensitivity was superior to the NO2 sensitivity in the concentration range of 20–100 ppm, and then SnO2 mixed with 5.0 wt% Cr2O3 was found to be the most suitable candidate for a NO sensor among the sensors tested. The increase in the breakdown voltage in air induced by the Cr2O3 addition was confirmed to arise from both the decrease in the particle size of SnO2 and the formation of micro p-n junctions at grain boundaries. The decrease in the particle size was also responsible for the increased NO and NO2 sensitivities, but the p-n junctions were suggested to play a more important role in promoting and stabilizing the chemisorption of NO at higher temperatures. 相似文献
6.
An exceptionally high Al3+ ion conducting polycrystalline solid based on the NASICON type structure was successfully realized within the system (AlxZr1−x)4/(4−x)Nb(PO4)3. The partial substitution of the smaller higher valent Nb5+ ion for Zr4+ helped stabilize and accommodate the mobile Al3+ ion into the NASICON like structure. The addition of boron oxide to the Al3+ ion conducting solid electrolyte, as a sintering additive, aided in the achievement of satisfactory mechanical strength and
density for practical use. Environmental gas sensors were fabricated by combining the (AlxZr1−x)4/(4−x)Nb(PO4)3 solid electrolyte with yttria stabilized zirconia (YSZ) and appropriate auxiliary electrodes. The Nernst-like electrochemical
sensors demonstrated rapid and reproducible response to CO2 and NOx, thereby promising excellent potential for environmental monitoring applications. 相似文献
7.
Han Byel Shim Ju Hyun Kang Jung Woon Choi Kwang Soo Yoo 《Journal of Electroceramics》2006,17(2-4):971-974
Potentiometric CO2 sensors were fabricated using a NASICON (Na1+x
Zr2SixP3−x
O12) thick film and auxiliary layers. The powder of a precursor of NASICON with high purity was synthesized using the sol-gel
method. Using the NASICON paste, an electrolyte was prepared on the alumina substrate through screen printing and then sintered
at 1000∘C for 4 h. In the present study, as new auxiliary phases, a series of Na2CO3-CaCO3 system was deposited on the Pt sensing electrode. The electromotive force (EMF) values were found to be linearly dependent
on the logarithm of the CO2 concentration in the range of 1000–10000 ppm. The device to which Na2CO3-CaCO3 (1:2) was attached showed good sensing properties at low temperatures. 相似文献
8.
Abstract High sensitive pyroelectric infrared (IR) sensors have been fabricated by using c-axis oriented La-modified PbTiO3 (Pb1–xLaxTi1?x/4O3, PLT) thin films. The PLT thin films were deposited on (100)-cleaved MgO single crystal substrates by intermittent rf-magnetron sputtering method. The PLT thin films have high figures of merit for IR sensor without a poling treatment. High performance pyroelectric IR sensors (single element type and linear array type) were fabricated by using PLT (x=0·1, γ=5·5x10?8 C/cm2K, ?r=200) thin films. The sensors have remarkably high D* of 3–6x108 cmHz1/2/W and very fast response. A new compact IR sensing system using the linear array sensor (8 elements) has been developed for a new type of room air-conditioner. This system can measure thermal distribution (8x64) by horizontal scanning of the vertical linear array. Image processing with neural network concept makes possible high-accuracy using a few data from the sensor elements. This sensing system provides ‘‘smart airconditioning'’to improve the comfortable control. 相似文献
9.
Li Wei Zhang Xiaopin Zhang Min Ye Peida 《Frontiers of Electrical and Electronic Engineering in China》2007,2(2):234-239
The article introduces an advanced approach of fiber grating strain demodulation based on the principle of polarized-light
interference. This method can solve the problem of cross sensitivity in fiber Bragg grating sensor. As for the yttrium vanadate
(YVO4) crystal polarized-light interferometer, if there are two different fiber Bragg gratings that have a π rad phase difference,
one is used for strain sensor and the other is used for temperature compensating. Then the problem of cross sensitivity can
be overcome. The analyses of the strain demodulation resolution show that with a decrease in crystal thickness the resolution
increases. The experiment shows that when the thickness of YVO4 crystal is 0.5 mm, the effect of cross-sensitivity will be reduced to 0.13 μɛ/°C, which is 1.6% of the effect used by only
one fiber Bragg grating for strain measure. And when the thickness is 0.1 mm the cross-sensitivity will be reduced to 0.006
7 μɛ/°C, which is less than 0.08%. Less thickness of crystal is beneficial for the resolution of strain measure, but the machining
of small thickness crystal is difficult. To solve this problem, a new scheme of polarized-light interfereometer with the structure
of double layer crystal was analyzed.
Translated from Acta Optica Sinica, 2006, 26(1): 19–24 [译自: 光学学报] 相似文献
10.
Beom-Keun Yoo Yong-Wook Park Chong-Yun Kang Seok-Jin Yoon Jin-Sang Kim 《Journal of Electroceramics》2006,17(2-4):1013-1017
This paper presents properties of saw acoustic wave (SAW) gas sensors to detect volatile gases such as acetone, methanol,
and ethanol by measuring phase shift. A dual-delay-line saw sensors with a center frequency of 100 MHz were fabricated on
128∘ Y-Z LiNbO3 piezoelectric substrate. In order to improve sensitivity of SAW sensors, a thin titanium (Ti) film as mass sensitive layer
was deposited using e-beam evaporation on the surface of the SAW sensors. In our investigation the response time and sensitivity
of SAW sensors were measured. The response time and sensitivity of SAW sensor with thin Ti film were strongly improved because
of changing electrical and mechanical properties in the mass sensitive layer. As a result, high sensitivity and fast response
time could be achieved by deposition of thin Ti film as mass sensitive layer on the surface of SAW sensor. It can be applied
for high performance electronic nose system by assembling an array of different sensors. 相似文献
11.
N. Matsushita K. Kondo S. Yoshida M. Tada M. Yoshimura M. Abe 《Journal of Electroceramics》2006,16(4):557-560
Ni0.2Zn0.3Fe2.5O4 films (1–5 μm thick) were deposited by spin spray ferrite plating from an aqueous solutions onto polyimide sheets at 90∘C. Their peel test and high-frequency permeability as well as noise suppression effects were investigated. The oxygen plasma
treatment on polyimide sheet surface improved the film adhesion. There was not visible crack on the bended film surface for
the Ni-Zn ferrite film thinner than 2 μm and was not peeled off even after the bending test of a million times. The films
exhibited excellent high-frequency permeability profile and a natural resonance frequency (where the imaginary permeability
reaches a maximum) f
r
was 370 ± 30 MHz. The transmission loss increased with the film thickness, reaching the maximum Δ P
loss = 70% at 8 GHz for the 5 μm-thick film. The reflection loss in the measured frequency range was S
11 < 10 % which is small enough for films to be used as the conducted noise suppressors. The value of Δ P
loss obtained for the 5-μm thick film was about 15% higher than that (Δ P
loss = 55 %) attained by the commercialized 50-μm thick noise suppressing sheet. 相似文献
12.
Bo-Yun Jang Beom-Jong Kim Young-Hun Jeong Sahn Nahm Ho-Jung Sun Hwack-Ju Lee 《Journal of Electroceramics》2006,17(2-4):387-391
BaTi4O9 thin films were grown on a Pt/Ti/SiO2/Si substrate using RF magnetron sputtering. A homogeneous BaTi4O9 crystalline phase developed in the films deposited at 550∘C and annealed above 850∘C. When the thickness of the film was reduced, the capacitance density and leakage current density increased. Furthermore,
the dielectric constant was observed to decrease with decreasing film thickness. The BaTi4O9 film with a thickness of 62 nm exhibited excellent dielectric and electrical properties, with a capacitance density of 4.612
fF/μm2 and a dissipation factor of 0.26% at 100 kHz. Similar results were also obtained in the RF frequency range (1–6 GHz). A low
leakage current density of 1.0 × 10−9 A/cm2 was achieved at ± 2 V, as well as small voltage and temperature coefficients of capacitance of 40.05 ppm/V2 and –92.157 ppm/∘C, respectively, at 100 kHz. 相似文献
13.
Film texture and ferroelectric behaviors of (Bi3.15Nd0.85)Ti3O12 (BNdT) of layered-perovskite structure deposited on Pt/TiO2/Si substrate are dependent on the film thickness. When the film thickness is reduced from ∼240 to ∼120 nm, BNdT grains evolve
from a rod-like morphology to a spherical morphology, accompanied by a decrease in average grain size. At the same time, P-E hysteresis transforms from a square-shaped hysteresis loop (2Pr ∼24.1 μC/cm2 at 240 nm) to a relative slimmer hysteresis loop (with a lower 2Pr = 19.8 μC/cm2 at 120 nm). The nonvolatile polarization (Δ P) shows a maximum at the film thickness of 160 nm, where Δ P was measured to be 14.7 μC/cm2 and 6.8 μC/cm2 at 5 V and 3 V, respectively. A small amount of excess bismuth in the film thickness of 130 nm, introduced by co-sputtering,
can lead to a much enhanced remanent polarization (2Pr of 21.3 μC/cm2 at 5 V and 15.2 μC/cm2at 3 V), which is promising for low voltage FRAM applications. 相似文献
14.
Marija F. Hribek Slavica S. Risti Bojana M. Radojkovi Zoran Lj. Filipovi Ognjen R. Risti 《International Journal of Numerical Modelling》2013,26(3):263-274
Comparative analysis of different, new gas sensing materials in surface acoustic wave chemical sensors is presented. Different gas sensing materials as polyaniline (PANI), Teflon AF 2400, polyisobutylene (PIB), polyepichlorohydrin (PECH) are considered. They are chosen according to the type of gas to be detected and the desired accuracy: Teflon AF 2400 thin film for the detection of CO2, PANI nanocomposites film that belongs to the group of conductive polymers for the detection of CO, NO2 and phosgene (COCl2), and PECH and PIB for the detection of dichloromethane (CH2Cl2, DCM). In the analysis, the simple and useful method of the complete analyses of gas chemical sensors is used. The method is based on the electrical equivalent circuit of the surface acoustic wave sensor. The method is very efficient and can be used for the optimal design of CO2 sensors. The results are compared with those presented in public literature and good agreement is obtained, demonstrating the validity of modelling. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
15.
Myung-Sic Chae Sang-Myung Lee Yong Kyoung Yoo Soo Hyun Lee Jinsik Kim Tae Song Kim Dong June Ahn Jeong Hoon Lee Kyo Seon Hwang 《Journal of Electroceramics》2014,32(4):383-389
The detection capability of microresonating sensors is decided by the resonant properties (mass sensitivity and quality factor) because the microresonating sensors have detection principle that the target material of small amount quantitatively detect by measuring the resonant properties change of microresonators. Mass sensitivity is important factor to evaluate minimum detectable mass of microresonating sensors. For the biomolecule detection in liquid, microresonaotrs have to keep the quality factor that can discriminate small frequency change when the liquid sample injected on the microresonating sensors. In order to study mass sensitivity and quality factor of the fabricated microdiaphragm sensors, Pt thin film with different thicknesses are deposited on the our Pb(Zr0.52Ti0.48)O3 layer-embedded microdiaphragm sensors. Increasing the mass sensitivity ranging from 1.68 to 36.61 Hz/ng which is found with the decreasing the width of squared microdiaphragms ranging 900 to 300 μm. The mass sensitivity of our microdiaphragm sensor stands comparison with microcantilever sensor of length scale of 200?~?300 μm. Moreover, we find that the quality factor is kept on more than 23 that was ten times better than microcantilever resonating sensor with length scale of 200 μm. 相似文献
16.
Naonori Sakamoto Tomoaki Watanabe Masahiro Yoshimura 《Journal of Electroceramics》2006,17(2-4):1075-1078
We have studied glass formable region in the Y2O3-CaO-Al2O3 system. An optimal composition for the amorphous phase formation was found in the pseudo-eutectic 12CaO⋅7Al2O3-CaYAlO4 system. An amorphous bulk plate of 10 × 25 × 1.8 mm was successfully fabricated using a simple molding technique. The fabricated
glass plate showed an IR absorption edge at around 5.6 μm. The crystallization of the glass sample was observed above 890∘C by an X-ray diffraction (XRD) and Thermogravimetry and Differential thermal analysis (TG-DTA). 相似文献
17.
Process optimization and properties of lead zirconate titanate (PZT) films for piezoelectric micromachined ultrasonic transducers
(pMUTs) for scanning probe devices will be presented. The goal of the work was a replacement of the tetragenic and mutagenic
solvent and a decrease of time-consuming PZT 2–methoxy ethanol (2MOE) route. An alternative diol-based solution synthesis
process was developed and “Design Of Experiment” (DOE) was used to achieve processing optimization for thick and crack free
films. Tight parameter control allowed to develop a highly reproducible PZT diol process. The crystallization behaviour of
crack-free PbZr0.53Ti0.47O3 films (1–5 μm) with oriented perovskite structure was examined by X-ray diffraction and surface analysis using scanning electron
microscopy. Piezoelectric and dielectric properties were examined. The effective transverse piezoelectric coefficient e
31,f of sol–gel processed films was investigated for 4 μm thick layers. Best properties were achieved with {1 0 0}-textured films,
where a remanent e
31,f value of −7.3 C/m2 was measured for 4.1 μm thick films. 相似文献
18.
Avneet Singh Anjali Sharma Nidhi Dhull Anil Arora Monika Tomar 《Integrated ferroelectrics》2018,193(1):72-87
AbstractIn the present work efforts have been made to develop microheater integrated gas sensors with low power consumption. The design and simulation of a single-cell microheater is carried out using ANSYS. Low power consumption (<35?mW) platinum micro-heater has been fabricated using bulk micromachining technique on silicon dioxide membrane (1.5?μm thin), which provided improved thermal isolation of the active area of 250?×?250?μm2. The micro-heater has achieved a maximum temperature of ~950?°C at an applied dc voltage of 2.5 V. Fabricated mircro-heater has been integrated with SnO2 based gas sensors for the efficient detection of H2 and NO2 gases. The developed sensors were found to yield the maximum sensing response of ~184 and ~2.1 with low power consumption of 29.18 and 34.53?mW towards the detection of 1?ppm of NO2 gas and 500?ppm of H2 gas, respectively. 相似文献
19.
Hitoshi Takamura Hiroshi Sugai Masato Watanabe Takehiro Kasahara Atsunori Kamegawa Masuo Okada 《Journal of Electroceramics》2006,17(2-4):741-748
The preparation and oxygen permeation properties of the (Ce0.8Pr0.2)O2−δ − x vol% MnFe2O4 composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce0.8Pr0.2O2−δ, an oxygen flux density of 6 μmol⋅cm−2⋅s−1 (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000∘C. Unlike composites consisting of Gd-doped CeO2 and MnFe2O4, the oxygen permeability of the (Ce0.8Pr0.2)O2−δ – x vol% MnFe2O4 composites was almost constant regardless of the volume fraction of MnFe2O4; however, the optimum volume fraction of MnFe2O4 was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere.
In addition, the surface modification of the (Ce0.8Gd0.2)O2−δ – 15 vol% MnFe2O4 composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm2 on the both side of the 0.3 mm-thick (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite increased the oxygen flux density from 0.30 to 0.76 μmol⋅cm−2⋅s−1 in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by
a large pO2 gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition
of the LB film. 相似文献
20.
The thick film electrodes (cathode) have been developed via screen printing using LiCoO2 paste to improve the discharge capacity of lithium ion micro-batteries. The LiCoO2 pastes were formulated using the mixtures of LiCoO2 powder as a functional material, carbon black as a conducting agent, ethyl cellulose and terpineol as a vehicle, and Emphos
PS-21A as a dispersant. Depending on the amount of carbon black, the average and maximum surface roughnesses varied from 0.54
to 1.00 μm and 6.2 to 18.7 μm respectively. The internal resistance in the paste electrodes could also be controlled to 120
KΩcm−2 by the addition of carbon black in the pastes. The thickness of the printed film is independent of the paste composition,
but it decreased from 15 to 6 μm with the increase in screen mesh number from 250 to 500. The initial specific discharge capacity
of the printed cathode which was prepared using the mixture Ag-coated LiCoO2 powder improved to 180 μAhcm−2. 相似文献