Micromachined water vapor sensors: a review of sensing technologies

Fenner, R.; Zdankiewicz, E. M.

doi:10.1109/7361.983470

Cited by 145 publications

(89 citation statements)

References 27 publications

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“…Humidity related properties can also be checked by connecting the MOS device to the timer circuit [17]. RH is the measure of the amount of moisture in ambient air as a percentage of the total amount of moisture that the air could hold at a given temperature.…”

Section: Timer Circuitmentioning

confidence: 99%

Characterization of Al2O3 thin films prepared by spray pyrolysis method for humidity sensor

Shamala

Murthy

Radhakrishna

et al. 2007

Sensors and Actuators A: Physical

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Al 2 O 3 thin films were deposited on silicon, steel and nickel substrates to fabricate MOS and MIM devices. The films were prepared by spray pyrolysis method using a spray solution of Aluminium acetyl acetonate dissolved in dimethyl formamide and this solution was sprayed on to the hot substrates at temperatures of 300 and 350 • C. The films were amorphous in nature as detected by XRD. Capacitance versus voltage (C-V), current versus voltage (I-V) and capacitance versus frequency (C-f) measurements were taken for these films. MOS capacitor was used as a humidity sensor using the home made humidity sensor setup. ac capacitance and parallel resistance of the capacitor as a function of humidity were studied. It was found that the capacitance value increases from 0.537 to 2.073 nf with the increase in relative humidity (RH) from 0 to 90% and the resistance decreases from 153 to 93 k with the increase in relative humidity from 20 to 87%. Relative dielectric constant versus temperature measurements were done for the MOS device to check its ferroelectric behavior and its critical temperature was found to be around 66 • C. MIM device was also used as a humidity sensor by measuring capacitance as a function of time by keeping the sensor in a dessicator. The 555 timer circuits were used to check the sensor behavior of the MOS device. Volume resistivity and breakdown electric field of the film deposited on steel were measured and found to be 5 × 10 11 cm and 5 MV/cm, respectively.

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Section: Timer Circuitmentioning

confidence: 99%

Characterization of Al2O3 thin films prepared by spray pyrolysis method for humidity sensor

Shamala

Murthy

Radhakrishna

et al. 2007

Sensors and Actuators A: Physical

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“…5,7,8 Different mechanisms to explain the origin of humidity effects for metal oxide materials have been proposed, including temperature-dependent or voltage-dependent chemisorption. 7,[9][10][11] Here we show that electrochemically prepared ZnO rectifying (Schottky) junctions have current-voltage relationships that are influenced by relative humidity changes at ambient temperatures due to a water electrolysis mechanism, 12,13 and that their responses can be qualitatively changed by varying electrolyte pH during electrodeposition or by adding post-deposition coatings. These findings highlight the effect that wet or humid environments can have on electron transport materials.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9] Our alternative approach is to use electrochemical deposition to form the rectifying junction. Electrodeposition is a technique that has been used to make ZnO thin films, [15][16][17][18][19] but reports of its electrical resistivity have more often been associated with its function in multilayer systems [20][21][22][23] rather than ZnO alone.…”

Section: Introductionmentioning

confidence: 99%

Focused-Ion-Beam-Assisted Magnet Fabrication and Manipulation for Magnetic Field Detection Applications

Campanella

Real

Díaz-Michelena

et al. 2009

ACS Appl. Mater. Interfaces

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The effect of synthesis conditions and . . . AbstractElectrochemically produced ZnO/metal rectifying (Schottky) junctions can exhibit consistent barrier heights and high rectifying ratios when prepared using optimized electrolyte pH (6.5) and applied voltage (≤-1.1 V vs. Ag/AgCl) conditions. An increase in soft breakdown for more acidic deposition electrolytes (pH 4) correlates with a diminished preferred orientation in the resulting ZnO electrodeposit. Forward-biased junctions exposed to increased relative humidities show increased current as a result of protonic conduction from water hydrolysis at the ZnO/air interface.At moderate to high relative humidities (50 − 85% RH), hydrophobic coatings improve the quality of the rectifying response by changing the wetting properties of the ZnO surface. Our findings suggest that electrodeposition, in conjunction with post-deposition surface coatings, can offer improved functionality for electron transport materials in wet or humid environments.

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“…Although the resistive humidity sensors are easily fabricated and the readout circuits are simple, the drawbacks of long recovery time and low stability limit their applications [2,3]. The capacitive humidity sensors offer several advantages such as low power consumption, wide temperature range, and long-term stability, but the readout circuits may be complex for high precision applications [6,7].…”

Section: Introductionmentioning

confidence: 99%

A Surface Micromachined CMOS MEMS Humidity Sensor

Huang

Zhao

et al. 2015

Micromachines

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This paper reports a CMOS MEMS (complementary metal oxide semiconductor micro electromechanical system) piezoresistive humidity sensor fabricated by a surface micromachining process. Both pre-CMOS and post-CMOS technologies were used to fabricate the piezoresistive humidity sensor. Compared with a bulk micromachined humidity sensor, the machining precision and the sizes of the surface micromachined humidity sensor were both improved. The package and test systems of the sensor were designed. According to the test results, the sensitivity of the sensor was 7 mV/%RH (relative humidity) and the linearity of the sensor was 1.9% at 20˝C. Both the sensitivity and linearity were not sensitive to the temperature but the curve of the output voltage shifted with the temperature. The hysteresis of the humidity sensor decreased from 3.2% RH to 1.9% RH as the temperature increased from 10 to 40˝C. The recovery time of the sensor was 85 s at room temperature (25˝C).

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Micromachined water vapor sensors: a review of sensing technologies

Cited by 145 publications

References 27 publications

Characterization of Al2O3 thin films prepared by spray pyrolysis method for humidity sensor

Characterization of Al2O3 thin films prepared by spray pyrolysis method for humidity sensor

Focused-Ion-Beam-Assisted Magnet Fabrication and Manipulation for Magnetic Field Detection Applications

A Surface Micromachined CMOS MEMS Humidity Sensor

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