Surface Acoustic Wave Sensors for Ammonia Detection at Room Temperature Based on SnO₂/Co₃O₄ Bilayers

Abstract

The selectivity of a SAW (surface acoustic wave) sensor, with a Co3O4 sensitive thin film for NH3 (ammonia) and the influence of SnO2 on its sensitivity, was studied. Thin films were deposited by pulsed laser deposition (PLD) on quartz SAW sensor substrates. Two sensors with different types of sensitive films were developed: a Co3O4 thin film sensor (S1) and a SnO2/Co3O4 thin film sensor (S2). The sensitive films were deposited in conditions which ensured a porous structure. The sensors were tested in the presence of three gases: NH3, methanol, and toluene. The selectivity of Co3O4 for NH3 was determined from the difference in the frequency shifts of the sensor for NH3 and for VOCs (volatile organic compounds). The positive influence of SnO2 on the sensitivity of sensor S2 was observed from the lower limit of detection (LOD) of this sensor and from the differences in frequency shifts between sensor S1 and sensor S2.

Development of Pd/TiO2 Porous Layers by Pulsed Laser Deposition for Surface Acoustic Wave H2 Gas Sensor

“…This phenomenon is due to changes in the mass or acoustoelectric properties of the sensitive layer in the presence of the gas [14]. This type of sensors has attracted attention through their features as small size, low cost, ease of fabrication, fast response, remarkable sensitivity, satisfactory stability, wireless operation [15,16]. SAW sensors have been developed for the detection of hydrogen [15,17] volatile organic compounds [18], ammonia [16], hydrogen sulfide [1], explosives [19], toxic gases [20], etc.…”

ZnO Metal Oxide Semiconductor in Surface Acoustic Wave Sensors: A Review

“…The development of new materials, with complex and specific properties for a certain application has become a challenge for researchers. For example, the development of materials as thin films on different substrates led to a revolution in several fields, such as catalysts [ 53 ], optical layers [ 54 ], conductive layers [ 55 ], biomedical applications [ 56 ], sensors [ 22 ], and protective layers [ 57 ]. There are many methods that can be used to deposit thin films, including spin coating [ 58 , 59 ], pulsed laser deposition [ 60 , 61 ], dip-coating [ 62 , 63 ], chemical vapor deposition [ 64 , 65 ], evaporation [ 66 , 67 ], and Radio Frequency (RF) magnetron sputtering [ 68 , 69 ].…”

“…The most important features of a SAW sensor, sensitivity and selectivity, are affected and improved by means of the sensitive thin film. The development is, therefore, very important in research aimed at obtaining an outstanding performance in the detection of various gases [ 22 , 80 , 82 , 83 ]. Although a wide range of materials has been studied related to the field of sensors, this is still an active domain of research, so that a review bringing together recent results in the domain, including the considerable disadvantages still present, is an important starting point for future research.…”

“…A considerable advantage of this type of sensor is that it is versatile, which allows for adaptation to different applications [ 21 ]. SAW sensors are used for the detection of gases [ 22 , 23 , 24 ], as well as for the detection of liquids or other changes in the environment, such as pressure [ 25 ], humidity [ 26 ], the presence of UV radiation [ 27 ], and for chemical and biological applications [ 28 , 29 ]. In this work, we focused on the study of SAW sensors for gas detection.…”

Love Wave Sensors with Silver Modified Polypyrrole Nanoparticles for VOCs Monitoring

“…Surface acoustic wave (SAW) sensors have attracted great attention thanks to their sensitivity, low limits of detection (LOD), room temperature operation, low power consumption, relatively simple architecture, small dimensions and ability to work in wireless mode [6]. Moreover, previous literature on SAW sensors states the feasibility to sense gases and vapors by using sensitive materials such as semiconducting metal oxides [7], polymers [8], graphene oxide [9] and carbon nanotubes [10]. Apart from the competing advantages of those sensing materials, polymers-based SAW structures demonstrated improved performance in gas sensing, owing to their low density and shear velocity.…”