W artykule przedstawiono wstępne badania z wykorzystaniem metody z akustyczną falą powierzchniową (AFP) do wykrywania w mieszaninie powietrza śladowych ilości cząsteczek DMMP (Dimetylometylofosforan), który jest powszechnie wykorzystywany do symulacji obecności sarinu - gazu bojowego z grupy BŚT (Bojowe Środki Trujące). Elementem sensorowym jest warstwa polimeru fotoprzewodzącego poli(3- heksylotiofenu) typu regioregularnego ((RR) -P3HT) wytworzona metodą rozpylania w powietrzu na powierzchnię modułu z AFP. Istotnym czynnikiem wykrywania DMMP było oświetlanie badanego polimeru za pomocą światła białego niewielkiej lampy żarowej.
EN
This paper presents the preliminary investigations using the SAW method for the detection of trace amounts of DMMP molecules (Dimethylmethylphosphate) in air mixtures, which is commonly used to simulate the presence of warfare agents like sarin gas. The sensor element is a layer of photoconductive polymer poly(3-hexylphosphate) of regioregular type ((RR)-P3HT) produced by airborne sputtering on the free surface of the SAW module. An important factor enhancing the ability of DMMP detection was lighting of the polymer by means of a white light of a small incandescent lamp.
The paper presents the results of numerical analysis of the SAW gas sensor in the steady and non-steady states. The effect of SAW velocity changes vs surface electrical conductivity of the sensing layer is predicted. The conductivity of the porous sensing layer above the piezoelectric waveguide depends on the profile of the diffused gas molecule concentration inside the layer. The Knudsen’s model of gas diffusion was used. Numerical results for the effect of gas CH4 on layers: WO3, TiO2, NiO, SnO2 in the steady state and CH4 in the non-steady state in recovery step in the WO3 sensing layer have been shown. The main aim of the investigation was to study thin film interaction with target gases in the SAW sensor configuration based on simple reaction-diffusion equation. The results of the numerical analysis allow to select the sensor design conditions, including the morphology of the sensor layer, its thickness, operating temperature, and layer type. The numerical results basing on the code elaborated numerical system (written in Python language), were analysed. The theoretical results were verified and confirmed experimentally.
The paper presents the results of an analysis of gaseous sensors based on a surface acoustic wave (SAW) by means of the equivalent model theory. The applied theory analyzes the response of the SAW sensor in the steady state affected by carbon monoxide (CO) in air. A thin layer of WO3 has been used as a sensor layer. The acoustical replacing impedance of the sensor layer was used, which takes into account the profile of the concentration of gas molecules in the layer. Thanks to implementing the Ingebrigtsen equation, the authors determined analytical expressions for the relative changes of the velocity of the surface acoustic wave in the steady state. The results of the analysis have shown that there is an optimum thickness of the layer of CO sensor at which the acoustoelectric effect (manifested here as a change in the acoustic wave velocity) is at its highest. The theoretical results were verified and confirmed experimentally.
Layered nanostructures of tungsten trioxide WO3-x about 62 nm thick, with a very thin film of palladium (about 3.3 nm) on the top, have been studied for gas-sensing application at temperatures 50.C and 120.130.C and low NO2 and NH3 concentrations in 6%, 30% or 45% relative humidity in the air. Thin film WO3-x nanostructures were obtained by vacuum deposition on a common Si-SiO2 substrate at room temperature and 120.C. The palladium was coated by vacuum evaporation at room temperature and 4 �E 10.6 mbar on WO3-x layers obtained at two different substrate temperatures. The average rate of growth of the films, controlled by a QCM, was 0.1.0.2 nm/s. A multi-channel (four-channel interdigital gold electrodes) planar resistance gas sensor structure was used in the experiments. The surface of the nanostructures was characterized by means of the AFM method. Good sensor results have been observed at these layered nanostructures with an increasing resistance for NO2 molecules and decreasing resistance for NH3 molecules in a humid air atmosphere. The interaction and recovery speed were higher in the case of the nanostructure obtained at room temperature.
Przedstawiono badania nowej struktury warstwowej typu: tlenek niklu-pallad w sensorowym układzie z akustyczną falą powierzchniową pod kątem detekcji wodoru w powietrzu. Wykonano strukturę warstwową z tlenkiem niklu (NiOx) 60 nm w technologii reaktywnego rozpylania magnetronowego, pokrytą palladem o grubości 18 nm, wykonanym metodą naparowania próżniowego. Specjalnie zaprojektowany i wykonany układ elektroniczny umożliwia detekcję częstotliwości różnicowej (różnica częstotliwości toru ze strukturą warstwową oraz toru swobodnego bez pokrycia). Przeprowadzono badania oddziaływań takiej struktury z wodorem w powietrzu w zakresie średnich stężeń, nieprzekraczających wartości 2,5%. Dla stosowanej temperatury oddziaływania ok. 35°C stwierdzono maksymalną czułość struktury w zakresie stężeń wodoru pomiędzy 2 i 2,5% w powietrzu. Zmiana częstotliwości (będąca miarą oddziaływania) w tej temperaturze dla ww. stężeń wynosiła około 600 Hz.
EN
Presented are the investigations of a new layered structure: nickel oxide - palladium in a sensor system with surface acoustic wave, from the point of view of hydrogen detection in air. The layered sensor structure was prepared by means of reactive sputtering technology - nickel oxide 60 nm and vacuum deposition technology - palladium 10 nm. The specialised electronic circuit allows detection of the differential frequency (the difference between frequency with layered structure and the free ones). The investigations of such a structure with medium concentrations of hydrogen not exceeding a safety value 2.5% in air has been performed. The maximum sensitivity is detected at the interaction temperature of 35°C - the maximum change in frequency is on the level 600 Hz between 2 and 2.5% of hydrogen.
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W artykule przedstawiono nową matrycową konstrukcję czujnika pomiarowego do detekcji stężeń gazów w mieszaninach gazowych. Zaproponowano wykorzystanie matrycy przetworników z akustyczną falą powierzchniową (surface acoustic wave, SAW), w której trzy przetworniki aktywne pokryte różnymi warstwami czułymi pełnią rolę czujników, a czwarty pasywny stanowi element odniesienia, pozwalający na kompensację oddziaływań wielkości wpływających, szczególnie temperatury. Jako materiał podłoża dla przetworników SAW wykorzystano piezoelektryk, niobian litu (LiNbCh), na którym umieszczono przetworniki palczaste (interdigital transducers). W każdym z trzech przetworników aktywnych nałożono cienką warstwę czułą, adsorbującą cząstki określonych gazów. Warstwy te wykonano z pięciotleneku wanadu, trójtleneku molibdenu oraz trójtleneku wolframu i wszystkie dodatkowo pokryto palladem. Omówiono również układ elektroniczny współpracujący z przetwornikami SAW. Przedstawiono wyniki badań opracowanego przetwornika matrycowego, obejmujących badanie stabilności czasowej oraz badanie wrażliwości na różne gazy.
EN
The new matrix transducer for gas detection is described in this paper. Applying of four elements matrix of sourface acoustic wave (SAW) converter is proposed. Three of them are covered by the sensitive layers and are active. The fourth (without sensitive layer) is the passive one and is used for temperature (and other influences) compensation. The LiNb03 (piezoelectric) is appllied as base plate for SAW converter. The thin film sensitive layers were made of V2O5, W03 and M0O3 for the three active SAW respectively, each additionaly coverd by palladium. A proper electronic circuit were designed and is described. The results of investigations of the desired multichannel transducer are presented. The time stability and sensitivity for gases vere determined.
Przedstawiono wyniki badań wpływu temperatury na stabilność częstotliwości sygnałów wyjściowych matrycowego czujnika gazów którego zasada działania polega na wykorzystaniu akustycznych fal powierzchniowych (AFP). Krótko opisano zasadę działania czujnika i konstrukcję przetwornika. Przedstawione wyniki wskazują na znaczne zmiany częstotliwości w stanie przed stabilizacją termicznych warunków pracy układu. Wahania częstotliwości w ustabilizowanej temperaturze pracy przetwornika są pomijalnie małe w stosunku do zmian wywołanych oddziaływaniem wybranych gazów.
EN
Results of investigations of temperature influence on multichannel gas sensor based on surface acoustic wave (SAW) are discussed. Ash description of investigated SAW transducer with electronic circui is given. The method of investigation is described. The obtained resi lead to the conclusion, that stabilization of thermal conditions of sensor is essential to achieve acceptable small changes of out frequencies. To shorten the time of thermal stabilization an additio heater and temperature control system may be used.
Przedstawiono badania nowych struktur warstwowych typu: tlenek metalu-pallad w czterokanałowym układzie z akustyczną falą powierzchniową w zastosowaniu do detekcji metanu oraz wodoru w powietrzu. Za pomocą technologii naparowania próżniowego wykonano trzy różne struktury warstwowe z tlenkami: wanadu (V₂O₅) 60 nm, molibdenu (MoO₃) 90 nm, wolframu (WO₃) 75 nm pokrytych palladem o grubości 14 nm. Specjalnie zaprojektowany i wykonany układ elektroniczny umożliwia jednoczesną detekcję trzech częstotliwości różnicowych (różnica częstotliwości każdego toru ze strukturą warstwową oraz toru swobodnego bez pokrycia). Wykonano badania oddziaływań tych struktur z metanem oraz wodorem w powietrzu w zakresie niskich stężeń (do 500 ppm dla metanu oraz 4% dla wodoru). Dla stosowanej temperatury oddziaływania ok. 25°C stwierdzono znacznie większe oddziaływania z metanem w porównaniu do wodoru.
EN
The investigations of the new layered structures: metal oxide-palladium in a four-channel system with surface acoustic wave is presented. Testing was carried out for methane and hydrogen gas in air. The three various structures layered with different metal oxide: V₂O₅) 60 nm, (MoO₃) 90 nm or (WO₃) 75 nm and the same palladium film (14 nm) were prepared by means of vacuum evaporation technology. The specialized electronic circuit allows simultaneous detection of three differential frequencies (the difference between frequency with layered structure and the free ones). The interaction of this structures with methane and hydrogen gas in air in the range of low concentrations (to 500 ppm for methane and 4% for hydrogen) are performed. The interaction with methane is much greater at the applied temperature ~25°C, in comparison to the hydrogen gas. The change in frequency is on the level of about 900Hz for 500 ppm concentration of methane in air.
A single thin film sensor structure of TiO2(~60nm) , has been studied for gas-sensing application at ~300C and ~400C. The sensor structures were obtained by RF sputtering technology from titanium target in a controlled atmosphere Ar:O2(3:1) in a vacuum 2x10-3mbar onto a LiNbO3 substrate (Y- cut Z-propagating) and glass substrate. The first structure was prepared making use the Surface Acoustic Wave method and the second - ( prepared in this same technological processes) onto a glass substrate with a planar microelectrode array is for simultaneously monitoring of the planar resistance of the structure. In the case of a SAW structure a very good results have been observed to ammonia gas - frequency are on the level of 300 Hz to 1500ppm of ammonia concentration in dry air. In the case of a hydrogen gas almost no frequency shift is observed, whereas to H2S gas the sensor response is not reversible. In all the measurements the electrical resistance of the TiO2was on the almost constant level - indicating only mass interactions.
The measurements of the resistance response to synthetic air of the SnO₂ thin film based sensor structures were carried out. The sensing SnO₂ films were deposited on alundum substrates in the rheotaxial growth and thermal oxidation (RGTO) process. The sensor responses were registered under dry and humid airflow during structure heating and cooling (within the temperature range from 20°C to 400°C). The maximum sensor sensitivity to O₂ exposition was registered at a temperature of about 275°C. The temperature reversibility of the studied sensor response was compared with that of a commercial SnO₂ thick film Taguchi sensor. In order to understand the relationship between the sensing and chemical properties of SnO₂ films, the in-depth chemical composition profiles were investigated using the scanning Auger microprobe equipped with an Ar⁺ ion sputtering system.
PL
Zaprezentowano wyniki pomiarów rezystancji cienkich warstw sensorycznych SnO₂ otrzymanych metodą reotaksjalnego wzrostu i termicznego utleniania (RGTO). Pokazano, że wytworzone warstwy są czułe na tlen zawarty w syntetycznym powietrzu. Zarejestrowano odpowiedź sensora na suche i wilgotne syntetyczne powietrze podczas wygrzewania i ochładzania próbki (w zakresie temperatur od 20 do 400°C). Sensor wykazywał maksimum czułości na tlen zawarty w syntetycznym powietrzu w temperaturze około 275°C. Porównano temperaturową zależność odpowiedzi (przy grzaniu i chłodzeniu) badanego sensora z komercyjnym sensorem Taguchi na bazie grubych warstw SnO₂. W celu określenia zależności między właściwościami sensorowymi a składem chemicznym próbki, zbadano głębokościowe profile składu chemicznego za pomocą skaningowego mikroanalizatora elektronów Augera z systemem bombardowania jonami Ar⁺.
Presented here are the preliminary results concerning a cadmium sulfide(CdS) thin films investigations in a Surface Acoustic Wave dual-delay line systems. The CdS films has been prepared by an open-boat, physical vapor deposition (PVD) process using chemically prepared CdS powder as starting material. The thicknesses of the CdS films was about 115nm and 268nm. These CdS films have been investigated from the point of view their sensitivity towards: nitrogen dioxide, sulphur dioxide, ammonia and H2S gases with different concentrations in dry air.
Bi-layer structures with two thicknesses of metal-free phthalocyanine ( ~120 and ~160 nm) but the same thickness of palladium (~20 nm), have been studied for hydrogen and carbon monoxide gas-sensing applications at ~30 °C and ~50 °C temperatures. The structures were fabricated in two different vacuum deposition processes (first the H2Pc film and followed by the Pd) onto a LiNbO3 Y-cut Zpropagating substrate for a SAW method. Additionally, using the same deposition techniques, the bi-layer structure was deposited onto a glass substrate with a planar microelectrode array for simultaneously monitoring of the planar resistance of the structure. A good correlation has been observed between these two methods; frequency changes for SAW method correlate with decreases of the bilayer structure resistance. These measurements can give information about the acousto-electric interactions between SAW and charge carriers in the bi-layer structure.
Presented here are the results concerning a hydrogen sensor based on a novel bilayer structure with lead and cobalt phthalocyanines in a Surface Acoustic Wave dual-delay line and electric systems. The sensor material consists of two layers produced in two different vapour deposition processes. The first one is a lead or cobalt phthalocyanine (~310nm PbPc or 200nm CoPc) layer, whereas the second is a ~20 nm thin palladium (Pd) film. This structure was simultaneously formed in a one of the SAW dual delay lines and on the interdigital electrodes of the glass substrate for electric measurements. These sensor structures have been investigated from the point of view their sensitivity towards: hydrogen, nitrogen dioxide and sulphur dioxide gases with different concentrations in dry air. Preliminary measurements of this two bilayer structures have been performed simultaneously in the same chamber for this same measurement conditions.
Presented here are the preliminary results concerning a polyaniline thin films investigations in a Surface Acoustic Wave dual-delay line and electric systems. The polyaniline films has been prepared by an open-boat, physical vapor deposition (PVD) process using chemically prepared polyaniline powder as starting material. These films were simultaneously formed in a one of the SAW dual delay lines and on the interdigital electrodes of the glass substrate for electric resistance measurements. The thickness of the polyaniline films was about 100 nm. These polyaniline films have been investigated from the point of view their sensitivity towards: nitrogen dioxide, sulphur dioxide, ammonia, H2S, carbon monoxide and hydrogen gases with different concentrations in dry air. Preliminary measurements of this two polyaniline films have been performed simultaneously in the same chamber for this same measurement conditions using an acoustic and electric methods.
Presented here are the results concerning a hydrogen sensor based on a novel bilayer structure in a Surface Acoustic Wave dual-delay line and electric systems. The sensor material consists of two layers produced in two different vapour deposition processes. The first one is a metal-free pthalocyanine (H2Pc) layer, whereas the second is a ~20 nm thin palladium (Pd) film. This structure was simultaneously formed in a one of the SAW dual delay lines and on the interdigital electrodes of the glass substrate for electric measurements. In such a bilayer structure detection of hydrogen in a medium concentration range (from 1% to 4 % in nitrogen) is possible, even at room temperature. Preliminary measurements of this two bilayer structures has been performed simultaneously in the same chamber for this same measurements conditions. A good correlation of results between these structures has been observed.
Presented here are the results concerning a hydrogen sensor based on a novel bilayer structure in a Surface Acoustic Wave dual-delay line system. The sensor material consists of two layers produced in two different vapour deposition processes.The first one is a 230 nm nickel phtalocyanine (NiPc) layer, whereas the second is a 20 nm thin palladium (Pd) film. This structure was 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 ?f. This frequency, depending on the operating frequency modes, is in range of 20 to 30 kHz, whereas he oscillator frequencies are in the range of 43.6MHz. The wavelenghts is 80um. In such a bilayer structure detection of hdrogen in a medium concentration range (from 1% to 4% in nitrogen) is possible, even at room temperature. For the investigated structure the interaction response depends on temperature. For the structure an interesting "interaction jump" has beeen detected, which is connected wht the phase trasition in the palladium film. At hidher temeperatures thisinteraction jump shifts in the direction of higher hydrogen concentrations.
Result concerning a hydrogen sensor based on a two-layer structure in a Surface Acousic Wave dual-delay line sustem are presented. The sensor material consist of two layeds performed in two different vapor deposition processes. The first one is a 720nm CuPc (or 110nm H2Pc) layer, the other one - a 20 nm thin palladium film. This structure was formed in a one of the dual-delay line system on a LiNbO3 Y-cut Z-propagation substrate. In such a multilayer structure can detect hydrogen in a medium concentration range (from 0.25% to 3% in nitrogen), even at room temperature. The sensor has a very good sensitivity, stability and is entirely reversible. The responce and recovery times are very short (-200s 0 800s), which is very important from the practical point fo view.
Results of the investigation of thin Pd layers as hydrogen sensors are presented. Two types of sensors are examined - resistance and optical sensors. Changes in measured signal as a function of hyfrogen concentration in hydrogen-nitrogen mixture are registered. The sensor is exposed either directly to the gas mixture or to the transformer oil, through wich the gas mixture passes. The hydrogen concentration in the mixture changes from 0.5% to 4%. Investigated sensors are sensituve enough in this concentration range, in both media. Changes of Pd film properties caused by hydrogen absorption are reversible except a few first exposures to the mixture. Obtained results confirm the possibility of developing simple sensor for detection of hydrogen gas in dissolved in the transformer oil.
Przedstawiono możliwości wykorzystania zjawiska propagacji akustycznej fali powierzchniowej do detekcji gazów. Oddziaływanie określonych zewnętrznych wielkości fizycznych na ośrodek propagacji, w tym na samą powierzchnię, wpływa na warunki graniczne zagadnienia propagacji fali powierzchniowej. W przypadku czujników gazu zaburzenie propagacji (prędkości i tłumienia) zachodzi wskutek zmian właściwości mechanicznych i/lub elektrycznych cienkiej warstwy sensorowej naniesionej na powierzchnię falowodu. Wyniki rozważań teoretycznych potwierdzono badaniami eksperymentalnymi.
EN
Presents theoretical possibilities of application of a SAW in gas sensors. Interaction of external physical quantity on propagation medium, including the surface, can affect SAW propagation. In gas sensors disturbance of SAW propagation is results from change of the mechanical as well as electrical properties of a thin active sensor layer placed on a piezoelectric surface. The experimental results also have been presented.
Interdigital transducers generating surface acoustic waves have found numerous applications. The present paper deals with an equivalent model of a single interdigital transducer as well as an S AW fifter complying with the PSpice programme for the analysis of electronic systems. The suggested model makes tt possible to take into account such effects as interelectrode reflections, losses along the acoustic path and the electromagnetic coupling between the transducers. The obtained results of the analysis of an interdigital transducer comply with the results obtained basing on an admittance model and delta-function model. The final aim is to model an SAW oscillator.
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