Gas Sensor Applications Research Articles

Performance Assessment of a JF-CP-TFET for Hydrogen Gas Sensing Applications

Abstract In this paper, a junction-free charge plasma tunnel field-effect transistor (JF-CP-TFET) is proposed and analyzed for the first time to sense hydrogen (H2) gas. Using junction-free and charge-plasma approaches, the proposed JF-CP-TFET-based sensor minimizes random dopant fluctuations, a large thermal budget requirement, and complex processes in the semiconductor sensor production process. The sensing performance of the JF-CP-TFET-based gas sensor is demonstrated by analyzing changes in the work function of the gate of palladium (Pd) catalytic metals, which are proportional to the pressure of H2 gas exposed at the metal gate surface. The presence of H2 gas has been demonstrated by variations of the DC/AC parameters of the proposed sensor, such as carrier concentration, energy band, electric field, transfer characteristics, threshold voltage (VTh), and subthreshold swing (SS). The sensitivity of the JF-CP-TFET-based sensor has been evaluated in terms of drain current (IDS), ION/IOFF ratio, VTh, and SS change in the presence and absence of H2 gas molecules. The sensing capabilities of the proposed JF-CP-TFET-based gas sensor demonstrate that it could potentially be employed for H2 gas detection with excellent sensitivity and reliability.

Surface Defect Generation on SnO2 Nanoparticles Using High-Energy Ball Milling for H2S Gas Sensor Applications

Hydrogen sulfide (H2S) is a highly toxic and dangerous gas with a flammable and corrosive nature, making the development of reliable gas sensors for its detection vital. This study investigated the enhancement in H2S gas sensing performance of commercial SnO2 powders after high-energy milling. SnO2 powders were subjected to high-energy milling for 30, 60, and 90 min and then were characterized using advanced techniques to evaluate their morphology, chemical composition, and crystallinity. The response of a pristine SnO2 gas sensor, and ones where the SnO2 was milled for 30, 60 and 90 min, were 2.46, 2.27, 3.01, and 1.98, respectively, to 10 ppm H2S at 300°C. Thus, the H2S gas sensing results revealed that the SnO2 powders milled for 60 min exhibited the highest sensing performance. This improvement in H2S sensing performance was attributable to the reduced particle sizes achieved through the high-energy milling process, which increased the surface area and created defects on the surface of the SnO2 particles, thereby enhancing the interaction between the gas molecules and sensor material. The smaller morphological size of the particles and surface defects subsequently promoted the resistance modulation crucial for H2S gas detection. This study demonstrates that high-energy ball milling can effectively boost the gas-sensing features of SnO2 powders. The findings can provide guidance for enhancing the gas-sensing capabilities of other resistive sensors.

Application of MOS gas sensors for detecting mechanical damage of tea plants

Mechanical damage of tea plant is a serious problem in tea production. This work employed metal oxide semiconductor (MOS) gas sensors and gas chromatography-mass spectrometer (GC-MS), as an auxiliary technique, to detect tea plants with different types of mechanical damage in different severities. Various algorithms were applied. The results showed the uniformity of the results of gas sensors and GC-MS. While, it was hard for gas sensors to discriminate among tea plants with different types of mechanical damage. However, the feasibility of gas sensors for predicting the damage severity in different damaged types based on gas sensors was proven, which was more meaningful. Finally, multi-layer perceptron neural networks (MLPNN) was employed and the results showed that the correct discrimination accuracy rate for damage severity was 99.07% for the training set and 95.83% for the testing set, which indicated that MLPNN was an excellent algorithm for damage severity determination. This study provided a new technique for mechanical damage of tea plant detection and was very meaningful for tea plant protection.

Ga-doped ZnO nanoparticles for enhanced CO2 gas sensing applications

Gallium-doped zinc oxide (GZO) has demonstrated significant potential in gas-sensing applications due to its enhanced electrical and chemical properties. This study focuses on the synthesis, characterization, and gas-sensing performance of GZO nanoparticles (NPs), specifically targeting CO₂ detection, which is crucial for environmental monitoring and industrial safety. The GZO samples were synthesized using a sol–gel method, and their crystal structure was determined through X-ray diffraction (XRD), confirming the successful incorporation of gallium into the ZnO lattice. X-ray photoelectron spectroscopy (XPS) was employed to analyze the samples’ elemental composition and chemical state, revealing the presence of Ga in the ZnO matrix and providing insights into the doping effects. Transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDS) was used to confirm the purity and elemental distribution of the synthesized samples, ensuring the homogeneity of the Ga doping. In-situ TEM measurements were also conducted on one of the three samples, with the smallest size. The experiment involved exposing the sample to argon (Ar) as a reference gas and carbon dioxide (CO₂) as the target gas to evaluate the sensor’s response under real-time conditions. The in-situ TEM provided nanoscale observation of changes in the crystal structure parameters, particularly the d-spacing, which exhibited significant alterations exceeding 3.2% when exposed to CO₂ and Ar gases. Furthermore, electron paramagnetic resonance (EPR) and optical joint density of states (OJDS) analyses were performed to examine the presence of paramagnetic defects and to comprehensively understand the electronic structure within the GZO sample, respectively.

ZnO nanorod arrays for gas sensor application growing via hydrothermal technique: effect of metal oxide decoration

ZnO nanorod arrays for gas sensor application growing via hydrothermal technique: effect of metal oxide decoration

Surface facet engineering of ZnIn2S4 via supercritical hydrothermal synthesis for enhanced NO gas sensing performance

In this study, we investigate the novel application of ZnIn2S4 as an NO gas detection device by precisely modulating its surface facets through crystal growth control in a supercritical water environment. The supercritical hydrothermal synthesis successfully transforms ZnIn2S4 from a flower-like structure into a hexagonal plate morphology, driven by the preferential growth of the basal plane (003) surface facet. This morphological control, which is unattainable in a subcritical environment, is evidenced by a substantial increase in the (003)/(011) facet ratio from 0.52 to 1.98 with rising temperature. NO detection results indicate that this surface morphology modification significantly accelerates sensor response, attributed to enhanced interaction between the ZnIn2S4 surface and NO gas, as well as reduced diffusion limitations compared to the flower-like morphology. The hexagonal plates exhibit a remarkably fast response time of approximately 25 s, in contrast to 181 s for the flower-like counterpart. These findings underscore the crucial role of surface facet engineering in optimizing the gas-sensing properties of ZnIn2S4, highlighting its potential for advanced gas sensor applications.

Low Power Gas Sensors: From Structure to Application.

Gas sensors are pivotal across industries, encompassing environmental monitoring, industrial safety, and healthcare. Recently, a surge in demand for low power gas sensors has emerged, driven by the huge need for applications in portable devices, wireless sensor networks, and the Internet of things (IoT). The practical realization of a densely interconnected sensor network demands gas sensors to have low power consumption for energy-efficient operation. This Perspective offers a comprehensive overview of the progress of low-power sensors for gas and volatile organic compound detection, with a keen focus on the interplay between sensing materials (including metal oxide semiconductors, metal-organic frameworks, and two-dimensional materials), sensor structures, and power consumption. The main gas sensing mechanisms are discussed, and we delve into the mechanisms for achieving low power consumption including material properties and sensor design. Furthermore, typical applications of low power gas sensors are also presented, including wearable technology, food safety, and environmental monitoring. The review will end by discussing some open questions and ongoing needs.

Characterization and enhanced carbon dioxide sensing performance of spin-coated Na- and Li-doped and Co-doped cobalt oxide thin films.

Recognizing the substantial effects of carbon dioxide on human health and the environment, monitoring CO2 levels has become increasingly vital. Owing to energy constraints and the widespread application of CO2 gas sensors, it is important to design cost-effective, more efficient, and faster response CO2 gas sensors that operate at room temperature and involve a low-cost technique. This study aims to develop a cost-effective and efficient CO2 gas detector that functions at room temperature and uses less power than traditional high-temperature CO2 sensors. In this study, we achieved this by employing innovative Co3O4 thin films with optimized spinel-structured p-type semiconductors through spin-coating, facilitated by Li and Na doping as well as Li/Na codoping. Doping with 3% Li/Na reduced the crystallite size from 92.4 to 8.03 nm and increased the band gap from 3.31 to 3.69 eV. At room temperature (30 °C), the sensor response improved significantly, increasing from 50% to 345.01% for 3% Li-Co3O4 upon the addition of 3% Na at a concentration of 9990 ppm. This performance surpasses that of most metal-oxide-based CO2 sensors reported in the literature. Additionally, this optimized sensor demonstrated a very short response time of 18.8 s and a recovery time of 16.4 s at a CO2 concentration of 9990 ppm diluted with air. It outperformed other films in terms of sensitivity, stability, response and recovery times, and performance across a wide range of relative humidity levels (43-90%). The sensor exhibited superior selectivity for CO2 than for N2, H2, and NH3. Overall, the 3% Li, Na-Co3O4 sensor is well-suited for climate change mitigation and industrial applications.

Structural, electronic, optical, mechanical, and phononic bulk properties of tetragonal trirutile antimonate MSb2O6 (M = Fe, Co, Ni, or Zn): a first-principles prediction for optoelectronic applications

Abstract This work does an extensive analysis of the optoelectronic and mechanical properties of the tri rutile structure type 3d transition metal Antimonate MSb2O6 (M = Fe, Co, Ni, or Zn), for the first time, utilizing the pseudo-potential plane wave approach within the density functional theory framework. When calculating the structural, optical, and mechanical properties, the exchange–correlation interactions were studied using the GGA-PBE functional, whereas when computing electronic, it is analyzed using the HSE06 hybrid functional. The equilibrium lattice parameters exhibit good agreement with the available experimental results. The electronic properties were estimated using the GGA-PBE and HSE06 functionals. Based on the calculated electronic properties with the GGA-PBE functional, the FeSb2O6, CoSb2O6, and NiSb2O6 materials exhibit metallic behavior with energy gap values of 0 eV, while ZnSb2O6 is a semiconductor with a narrow direct band gap (Γ–Γ) of 0.5 eV. Furthermore, the computed band gaps using the HSE06 functional are 0 eV, 0 eV, 1 eV (Γ–Γ), and 4 eV (Γ–Γ) for FeSb2O6, CoSb2O6, NiSb2O6, and ZnSb2O6, respectively. Density of states diagrams were used to gain deeper insights into the characteristics of the energy bands. The optical properties of these compounds, such as the dielectric function, energy loss function, conductivity, reflectivity, refractive index, and absorption coefficient were investigated over the energy range of 0 to 40 eV. The materials exhibited a high absorption coefficient and a significantly low reflectivity within the UV–vis energy spectrum. The negative cohesive energy Ecoh implies the chemical (thermodynamic) stability of the trirutile MSb2O6 (M = Fe, Co, Ni, or Zn). Mechanical stability is confirmed by applying the Born stability criteria using elastic constants (Cij). The absence of imaginary frequencies in the phonon spectrum calculations confirms the dynamic stability of the studied compounds. These results are consistent with previous experimental research on these materials in photocatalysis and gas sensor applications. On the other hand, these compounds possess exceptional high and broad optical absorption UV range, making them suitable for use in next-generation ultraviolet photodetectors.

Impact of Substrate upon Morphology, Luminescence, and Wettability of ZnMgO Layers Deposited by Spray Pyrolysis

In this work, we report on a comparative study of the topology, luminescence, and wettability properties of ZnMgO films prepared by a cost-effective spray pyrolysis technology on GaAs substrates with (100), (001), and (111) crystallographic orientations, as well as on Si(100) substrates. Deposition on nanostructured GaAs substrates was also considered. It was found that film growth is not epitaxial or conformal, but rather, it is granular, depending on the nucleating sites for the crystallite growth. The distribution of nucleation sites ensured the preparation of nanostructured films with good uniformity of their topology. The observed difference in columnar growth on Si substrates and pyramidal growth on GaAs ones was explained in terms of the impact of chemical bonding in substrates. The films grown on GaAs substrates with a (001) orientation were found to be made of larger crystallites compared to those deposited on substrates with a (111) orientation. These effects resulted in a difference in roughness of a factor of 1.5, which correlates with the wetting properties of films, with the most hydrophobic surface being found on films deposited on GaAs substrates with a (111) orientation. The prospects for photocatalytic and gas sensor applications of films produced on flat substrates, as well as for plasmonic and other applications of films deposited on nanostructured substrates, are discussed, taking into account the results of the analysis of their photoluminescence properties.

Eu3+-doped MoO3 one-dimensional ice-lolly-like nanorods: Achieving red down-conversion luminescence and significantly enhancing triethylamine gas-sensing performance

A novel MoO3:x%Eu3+ one-dimensional (1D) ice-lolly-like nanorods with bifunctionality of luminescence and gas sensitivity are successfully prepared via electrostatic spinning and oxidative calcination. Among them, MoO3:x%Eu3+ 1D ice-lolly-like nanorods exhibit exceptional luminescence properties, with an emission peak at 616 nm when excited at a wavelength of 274 nm. The MoO3:x%Eu3+ 1D ice-lolly-like nanorods possess excellent gas-sensitizing properties to triethylamine (TEA) when they are fabricated to be gas sensors. The response value of MoO3:1%Eu3+ 1D ice-lolly-like nanorods gas sensor to 100 ppm TEA at 290 °C is 127.9, which is 11.5 times higher than that of the pure MoO3 (11.1) gas sensor. Furthermore, the MoO3:1%Eu3+ 1D ice-lolly-like nanorods gas sensor exhibits an ultra-fast response/recovery time (1 s/14 s). In addition, doped Eu3+ at the MoO3 interface leads to enhanced electronic and catalytic properties, thereby leading to a significant improvement in the gas-sensing performance of MoO3. More importantly, the doping of Eu3+ can simultaneously achieve excellent red down-conversion luminescence performance and enhance the gas-sensitive properties of MoO3. This can be attributed to the fact that Eu3+ serves as both a luminescent center and a sensitizer for MoO3, achieving the effect of killing two birds with one stone. The possible mechanisms of photoluminescence and gas sensing are also proposed. This design idea introduces an innovative approach for rapidly detecting damage to the sensing coating of gas sensors, achieved by illuminating the sensing material with excitation light. This work offers insights for constructing novel bifunctional composites with luminescence and gas sensing, broadening the application of gas sensors.

Structural and Optical Characteristic of Fe10+ Ion Implanted Nanostructured WO3 Film for Gas Sensing Application

Structural and Optical Characteristic of Fe10+ Ion Implanted Nanostructured WO3 Film for Gas Sensing Application

Influence of isochronal heat treatment on spray-deposited mixed phase tin based thin films for ammonia gas sensor applications

The current work applied the spray pyrolysis (SP) approach to coat mixed-phase SnS thin films at 3500C, and then air annealed at 400,450,5000C for use in sensor and solar cells applications. A variety of methods were employed to evaluate the structural, morphological, compositional, optical, and electrical characteristics of synthesized mixed-phase films. Films annealed at 5000C are reported to have bigger crystal sizes, and all deposited SnS films exhibit the orthorhombic phase in addition to tetragonal phase of SnO2, with other visible secondary phases like SnS2,Sn2S3. Fourier transform infrared spectroscopy and Raman analyses verified the molecular structure and vibrational mode of SnS films. The Scanning electron microscopy tests reveal a consistent, size-varying two-dimensional flake like grain structure, while the optical studies show a variation in optical direct band-gap from 1.79-2.75eV. The Hall-effect shows that films subsequently annealed at 4000C have improved electrical properties. An efficient metal oxide semiconductor gas sensor was developed by applying mixed-SnS film on the conducting side of an indium tin oxide coated glass plate. To examine the sensor selectivity at room temperature, a variety of test gases, such as NO2, H2S, C2H5OH, NH3, were purged at different concentrations. The optimum working temperature and concentration for NH3 selective gas have been determined to be 3500C and 5ppm. The sensor sensitivity is found to be maximum at operating temperature of 2000C towards NH3 gas. An inexpensive, fabricated MOS-gas sensor based on mixed-phase SnS can be easily mass produced and may find potential applications in industrial and environmental monitoring.

PPY: PVA Blend Enhanced with Metal Salt for Gas Sensing Applications

PPY: PVA Blend Enhanced with Metal Salt for Gas Sensing Applications

Synthesis and Characterization of TiO2 Nanotubes for High-Performance Gas Sensor Applications

In this study, we investigated the fabrication, properties, and sensing applications of TiO2 nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO2 nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO2 nanotube was found to be suitable for NO2 gas sensor applications. With an oxidation time of 15 min, its detection of NO2 gas showed a good result at 250 °C, especially when exposed to a NO2 gas flow of 100 ppm, where a maximum NO2 gas response of 96% was obtained. The NO2 sensors based on the TiO2 nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

A DFT study of SF6 decomposition products (H2S, SO2, and CS2) adsorption and detection on Pd-ZnO/SnS2 ternary composites

Real-time and accurate detection of SF6 decomposition products is a crucial approach to diagnosing internal faults of gas-insulated switchgear (GIS). However, the limited sensitivity and selectivity of SnS2 gas sensors have hindered their further development and application. This study employs density functional theory to design the optimal Pd-ZnO/SnS2 monolayer structure and investigate its adsorption behavior toward H2S, SO2, and CS2. The findings indicate that Pd atom doping and ZnO nanoparticle incorporation significantly enhance the conductivity of the SnS2 monolayer, reducing the band gap to 0.54 eV and lowering the work function by 5.019 eV. Regarding gas adsorption and sensing, the Pd-ZnO/SnS2 monolayer outperforms intrinsic SnS2 and ZnO/SnS2, showing the order in which SF6 decomposition products are selected is: CS2 > SO2 > H2S. Additionally, the sensitivity and recovery time of Pd-ZnO/SnS2 as a gas sensor were evaluated, confirming its excellent sensing performance for SO2 and CS2 detection. This study provides theoretical insights to advance the application of gas sensors in online insulation equipment monitoring.

Synthesis of ZnO NWs via Thermal Evaporation Technique

Zinc oxide nanowires ZnONWs were successfully synthesized on glass slides. The synthesis was conducted firstly by the deposition of 12 µm a thin film of Zn metal by thermal evaporation. Secondly,the coated film was annealed at a temperature of 600 ºC in air for four hours to grow the ZnO nanowires. It have been observed that the produced nanowires were grown in a vertical orientation and having a high density, very long, and a minimal aspect ratio. The crystal structure and morphology of ZnO nanowires were investigated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The UV-visible spectrophotometer was also used to calculate the optical parameters from the absorption spectrum and show a band gap energy around 3.25 eV. The crystal structure of the material was revealed to be polycrystalline with a preferred orientation in the direction of [101]. Small average crystallite size was calculated about 17nm The wires can be measured to have a length of around 10 µm with diameters ranging from 50 to 100 nm. This could be used for gas sensor applications. In addition, this ZnONWs structure has a maximum transmittance (100%) which can be a good candidate for many optoelectronic apllications.

Enhanced sensitivity and selectivity of ZnSe/PANI nanocomposite for Low-ppm NO2 detection at room temperature gas sensor application

The utilization of n-p composite-based gas sensors has garnered substantial interest within the field of gas sensing. This heightened attention can be attributed to the remarkable band alignment of the constituent materials which results in superior charge transfer rate, increased gas interaction sites and reduced optimum operating temperature. In this work, n-ZnSe/p-PANI composites were prepared by simple hydrothermal technique. The obtained X-ray diffraction pattern confirms the phase formation ZnSe, PANI and ZnSe/PANI composites. The pure ZnSe exhibits a sensing performance at a higher operating temperature of 100 °C, whereas ZnSe/PANI composite sample demonstrates an improved sensing response at 30 °C. Notably, the 20 wt.% composite sample (ZnSe–P2) achieved a maximum sensing response of 77 % towards 20 ppm of NO2 gas molecule. Additionally, the sensor exhibits the response time (Tres) of 112 s and recovery time (Trec) of 648 s, at an operating temperature of 30 °C. It also shows better stability, reproducibility and specific selectivity towards NO2 gas molecule. The superior sensing behavior of the ZnSe-P2 sensor can be ascribed to the development of a depletion region in the interface of ZnSe/PANI composites, which improved the charge transfer rate and increased the number of reactive sites. Therefore, the formation of n-p inorganic-organic composite strategy offers an effective approach for detecting NO2 gas molecules at lower temperature of 30 °C.

Correlation Between Structural, Electrical, and Optical Properties of ZnO:In for Ethanol Gas Sensing Application

Correlation Between Structural, Electrical, and Optical Properties of ZnO:In for Ethanol Gas Sensing Application

Pt-Ta microhotplate with low resistance temperature coefficient and low resistance drift

Micro thermal plates are widely used in various sensors in the aerospace and automotive fields. With the reduction of chip size and the development of MEMS, micro thermal plates are also moving towards integration. The device failure caused by the Pt film at high temperatures seriously affects the stability of the sensor, and degradation determines the sensor's operating temperature and service life. In this paper, Pt, Pt-Ta, and Pt-Pd microcalorimetric plates were prepared and analyzed for their sintering behavior, microstructure, electrical properties, and high-temperature stability using co-firing of resistors and alumina substrates. The film layers prepared by co-firing were better matched to the alumina substrate, and the sintered network of the film layers was better. The Pt-10 %Ta microthermal plate has a 46 % lower resistance temperature coefficient TCR compared to the Pt microthermal plate, and the resistance drift at 800°C is reduced to 2.11 %/Day. And even at 1100°C, the Pt-Ta system also has a very low resistance drift −12 %/Day (Pt26.6 % /Day and Pt-Pd35.18 %/Day) with improved high temperature stability. The addition of Ta allows the membrane layer to have fewer voids at high temperatures, reinforcing the high temperature characteristics of the resistance thermometer. It improves the stability and accuracy of the heating plate in high temperature gas sensor applications.