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Detection of hydrogen by means of single and bilayer sensor structures in surface acoustic wave system

Jakubik W. P.

Molecular and Quantum Acoustics

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2008

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Vol. 29

115-120

EN

Presented here are the results concerning an investigations of sensor properties of a single and bilayer sensor structures in a Surface Acoustic Wave systems. Among the single structure is: vacuum deposited 20nm palladium thin layer. Whereas the bilayer structures consists of two layers produced in two different vapour deposition processes. The first one is a phthalocyanine thin layer, whereas the second is a 20nm thin palladium (Pd) film. The following bilayer structures are investigated: Pd+CoPc, Pd+PbPc and Pd+H2Pc from the point of view their sensor properties towards hydrogen and other such toxic gases like: NO2, SO2 in synthetic dry air. These structures were formed in one of the dual delay line systems on a LiNbO3 Y-cut Z-propagation substrate, while the other serves as a reference, permitting an easy detection of the arising differential frequency Äf. This frequency, depending on the operating frequency modes, is in the range of 50kHz to 400 kHz, whereas the oscillator frequencies are in the range of 43,6MHz. The wavelength is 80um. Investigations have been performed in a two different temperatures similar to 220C and similar to 500C.

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Surface acoustic wave hydrogen gas sensor based on layered structure of palladium/metal-free phthalocyanine

Jakubik W.P., Urbańczyk M., Maciak E., Pustelny T.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2008

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Vol. 56, nr 2

133-138

EN

A layered sensor structure of metal-free phthalocyanine H2PC (160 nm) with a very thin film of palladium (Pd-20 nm) on the top, has been studied for hydrogen gas-sensing application at relatively low temperatures of about 30°C and about 40°C. The layered structure was obtained by vacuum deposition (first the phthalocyanine Pc and than the Pd film) onto a LiNbO3Y- cut Z-propagating substrate, making use of the Surface Acoustic Wave method, and additionally (in this same technological processes) into a glass substrate with a planar microelectrode array for simultaneous monitoring of the planar resistance of the layered structure. In such a layered structure we can detect hydrogen in a medium concentration range (from 0.5 to 3% in air) even at about 30°c. At elevated tem-perature up to about 40°C the differential frequency increases proportionally (almost linearly) to the hydrogen concentration and the response reaches its steady state very quickly. The response times are about 18 s at the lowest 0.5% hydrogen concentration to about 42 s at 4% (defined as reaching 100% of the steady state). In the case of the investigated layered structure a very good correlation has been observed between the two utilized methods - the frequency changes in the SAW method correlate quite well with the decreases of the layered structure resistance.

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Polyaniline thin films as a toxic gas sensors in SAW system

Jakubik W. P., Urbanczyk M., Maciak E., Pustelny T., Stolarczyk A.

Molecular and Quantum Acoustics

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2007

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Vol. 28

125-129

EN

Presented here are the preliminary results concerning an investigations of thin films of polyaniline (similar to100nm) as a toxic gas sensors in a Surface Acoustic Wave system. The investigations were performed with different concentrations of the following toxic gases: NO2, SO2, CO, H2S and hydrogen in synthetic dry air. These thin films were made by vacuum deposition technique and formed in one of the dual delay line systems on a LiNbO3 Y-cut Z-propagation substrate, while the other serves as a reference, permitting an easy detection of the arising differential frequency Delta f. This frequency, depending on the operating frequency modes, is in the range of 50kHz to 400 kHz, whereas the oscillator frequencies are in the range of 43,6MHz. The wavelength is 80um.