Gas sensors based on metal oxide nanostructures are in demand for the safety of human health and protection from environmental pollution. This type of sensors is more attractive in modern life for electronic devices because of low cast, more efficient, high reliability, fast response, more selective, and simplicity. In this paper we report undoped and PbO doped SnO2 thick film to study its microstructural and sensing behaviours. Three samples have been fabricated using screen printing technique on an alumina substrate and this is SnO2 (S1) and 1wt% PbO doped SnO2 (S2 and S3) at 800 0C and 900 0C. XRD and AFM techniques are used to observe the structural behaviours and it is found that the crystallite size decreases with PbO doping. The sensing properties such as sensing response, selectivity and transient time of the deposited thick films were studied at 200°C for various test gases such as ethanol, LPG and acetone concentrations (0–5000 ppm level). We also found that the response of sensor S3 to the test gas ethanol is ~ 3.38 times of LPG and ~ 1.95 times that of acetone. The response and recovery times of the ethanol gas for S3 sensor are 41s and 125s, respectively. Therefore, the deposited sensor S3 is a more suitable sensor for the test gas ethanol than LPG and acetone at 200 0C.
Research Article
Sensing performance of lead monoxide (PbO) doped tin oxide thick film gas sensor
https://doi.org/10.21203/rs.3.rs-2718308/v1
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PbO-SnO2
ethanol
sensing response
selectivity
Semiconductor SnO2 films are widely used for many applications such as solar cells, optical devices, oxidation catalysts, sensing applications of volatile organic compounds (VoCs) (Trinh et al 2011). Since SnO2 materials have wide band gap is 3.6eV at possessing a rutile-type tetragonal structure (Kumar et al 2020, Sharma et al 2022). Various novel metals such as CdS, Pd, Cd, and Ni are used as a dopant to improve the sensitivity, selectivity and transient time of SnO2(Sirohi et al 2021, Mohanpriya et al 2013, Asaithanmbi et al 2021, Yadav et al 2010, Salame2020, Nagirnyak et al 2016,Xu et al 2021,Gao et al 2020, Divya et al 2020). During the past decades, oxide-based semiconductors such as SnO2, ZnO, In2O3, CdO, etc. have attracted immense attention of researchers in nanotechnology at the nanoscale level due to their extraordinary structural, morphological, sensing behavior etc. The gas sensing properties of these oxide materials are tunable, which is why they are the basis for a variety of modern smart and functional materials(Robles et al 2018). Ethanol is volatile organic compound (VOC) and it is most harmful to human health including various types of toxicity. Due to the toxic behavior of ethanol, various researchers have studied the sensing parameters for the detection of ethanol gas.T. Maekawa et al 1992demonstrated theSnO2based gas sensor for detection of ethanol gas. They explain the sensing properties for 0.5 wt.% Pd-SnO2, 5 wt% La2O3-SnO2 and 0.5 wt% Pt-SnO2sensor, and found that maximum response for ethanol concentration (100–10000 ppm) at 300 0C.T. Tharasika et al 2019 reported that selective detection of ethanal gas for ZnO-SnO2 thin film using spray pyrolysis technique and they found that, Zn:Sn = 3:1 reacts faster, more selective, Highly sensitive to ethanol gas. Huyn et al 2017 demonstrated that PbO-SnO2 nanowires are used for ethanol gas detection. They observed that PbO-SnO2 sensor gives higher sensitivity towards ethanol as compared to other test gases like toluene, acetone, benzene, methanol. Furthermore, they discussed the sensing mechanism of PbO-SnO2 nanowires for ethanol gas. Vishwakarma et al 2021 studied the morphological, structural and ethanol gas sensing behaviours of Pd-SnO2 thick film. They interpreted the gas sensing parameters and found that the Pd-SnO2 thick film has a fast response, highly sensitive to the test gas ethanol (5000 ppm) at 200 0C due to extreme reduction in grain size.Bhatia S. et al. 2017 investigated the gas sensor behavior of ZnO nanoparticles for the detection of ethanol gas. They observed that ZnO nanoparticles are prepared by two methods namely thermal evaporation (PVD), simple heat treatment. They found that ZnO nanoparticles prepared by thermal evaporation method showed maximum response to 50 ppm ethanol gas at 250 0C. Additionally, they confirmed that the thermal evaporation technique is an effective method for detecting ethanol gas. Considering the above literature, in the present work, we fabricated PbO-SnO2 thick film sample and studied its microstructure and sensing properties, including sensing response, selectivity and detection of ethanol, acetone and LPG (0-5000 ppm) at 200 0C.
We fabricate threesamples such as undoped SnO2 (S1) and 1wt PbO doped SnO2at 800 0C (S2), and 1wt PbO doped SnO2 at 900 0C (S3) for detection of VOCs. The response of the deposited sensor is calculated with different concentrations of the test gas ethanol, acetone and liquid petroleum gas (0-5000 ppm) at 200 0C and the experimental setup is described in an earlier paper (Vishwakarma et al 2021). Using a DC power supply (DL-3203) and multimeter (Aplab107-N), we measured the corresponding change in device resistance after the sensor is exposed to different concentrations of the target gas in an air environment.
3.1. Microstructural Properties:
The surface modification of the deposited film is observed with the help of XRD and AFM techniques. We obtained XRD data with the help of Cu-Kα1 radiation and wavelength 1.5406 Å of D-8 advanced instrument (Vishwakarma et al 2019). The XRD peaks of the diffraction pattern represent planes (100), (110), (111), (101), (002), (102) and (220) at diffraction angles ~ 25.70, 26.20, 29.10, 34.20, 35.90, 38.30, and 42.70 respectively and which is shown in Fig. 1. The obtained diffraction peaks and associated planes justified the tetragonal structure of SnO2. We estimated the crystallite size of the deposited sensor using the Debye–Scherrer formula: D = K. λ/ β.cos θ (Vishwakarma et al., 2018), where λ = 1.5406 Å; K = 0.94; θ = diffraction angle and β = full width at half maxima (FWHM).We found that the average crystallite size of the fabricated sensors is 31.5 nm, 27.1 nm and 22.9 nm for S1, S2 and S3, respectively.It is clear from Fig. 1 that the diffraction peak shifts to the right on the (101) plane, the intensity decreases and the crystallite size also decreases with PbO doping in SnO2.Therefore, reducing the crystallite size of the deposited film may be applicable for gas sensing behaviour for VOCs gases.
AFM techniques are used for the analysis of surface morphological behaviour of fabricated devices. Fractal terms such as grain size, RMS roughness, kurtosis, skewness etc. have been reported by AFM analysis of the deposited film (S1 and S3). We used WSxM.5.0 Developed 8.5 software for plotting the AFM data. The two-dimensional and three-dimensional structures of the AFM for sensors S1 and S3 are shown in Fig. 2 (a–d). Figure 2shows that the grain size for sensors S1 and S3 are ~ 60 nm, ~ 45 nm, and the rms roughness is ~ 48 nm, ~ 31.0 nm, respectively. Srivastava et al (2009) studied the gas sensing behavior of Pd-SnO2 sensor for liquefied petroleum gas and they show that tin oxide has a small increase in crystallinity with Pd(0.25wt%) in SnO2. However, in this paper we found a large reduction (39.1%) in the crystallite size with 1 wt% PbO-SnO2. The modification of grain size and surface roughness of PbO-SnO2 film improves the sensing behaviour towards test gas.
Figure 4. AFM two-dimensional structures (a) S1 sensor (b) S3sensor andThree-dimensional structures (c) S1 sensor (d) S3 sensor.
3.2. Gas sensing properties.
3.2.1. Sensing response:
The 3S (SSS) parameter are used in the gas sensing field and are sensitivity, selectivity, and stability. The gas sensor responses are estimated with different concentrations of acetone, ethanol and liquefied petroleum gas (0-5000 ppm level) for deposited sensor at 200 0C in air environment. The change in resistance of the sensor is calculated for exposure to the test gas (ethanol, acetone and LPG) and the formula is as follows: (Vishwakarma et al 2021)
R = [ \(\frac{Ra-Rg}{Ra}\) ] ×100 (1)
Where, Ra = resistance in air atmosphere, Rg = resistance in the presence of test gas and R = response value. Initially, the sensitivity of the sensor was measured by different concentrations of the test gas (0-5000 parts per million (ppm)) in an air environment at 200 0C. It is obtained that the sensor has a peak response to S3 at 5000 ppm of the test gas ethanol. The behaviour of the sensing response has been found to be non-linear with the concentration of ethanol and is in agreement with previously reported results (Tan et al 2015). The sensing response values of the deposited film S1, S2 and S3 for ethanol, LPG and acetone are shown in Table 1. Figure 3(a) shows the response of sensors S1, S2 and S3 to ethanol at 200 0C. Figure 3(a) shows that as the concentration of ethanol increases, the response value increases and is as high as 88% for S3 at 200 0C. The response of S2 and S3 sensors to ethanol gas is 80% and 25%, respectively. Figure 3(b) shows the response of sensors S1, S2 and S3to acetone gas and it is 27%, 60% and 45%, respectively. The corresponding values for liquefied petroleum gas are 13%, 20% and 26% and are shown in Fig. 3(c). The comparison of the response value of sensors S2 and S3with different concentrations of ethanol, acetone and liquefied petroleum gas is displayed in Fig. 4(a) and 4(b). It is clear from Fig. 4 that the sensor S3 has maximum response for ethanol gas, and it is ~ 3.38 times that of LPG and ~ 1.95 times that of acetone. It is seen that sensor S3 results in a remarkably improved response for ethanol gas over LPG and acetone. It is observed that the results of sensor S3 respond better to ethanol gas as compared to LPG and acetone. A peak response of 88% is obtained for 5000 ppm ethanol at 200°C and which is a much higher value than the 200-ppm ethanol reported previously using PbO-SnO2 nanowires at 300 0C.
| Sensor | Sensing response (%) | Selectivity (%) | ||||
|---|---|---|---|---|---|---|
| Ethanol | Acetone | LPG | Ethanol | Acetone | LPG | |
| S1 | 25 | 27 | 13 | 38.5 | 41.5 | 20.0 |
| S2 | 80 | 60 | 20 | 49.7 | 37.9 | 12.4 |
| S3 | 88 | 45 | 26 | 55 | 28.1 | 16.9 |
3.2.2. Selectivity:
Selectivity is one of the most important parameters in the gas sensing field. The selectivity of the gas sensor is calculated as follows:
where Si is the peak response of the gas whose relative value is predicted and ΣSi is the sum of the peak response value of all target gases (Vishwakarma et al 2018). Using Eq. (2), we calculate the selectivity deposition sensor for the test gases ethanol, LPG and acetone. The observed value of selectivity of ethanol, LPG, and acetone for sensors S1, S2, and S3 are listed in Table 1. The selectivity of ethanol, LPG, and acetone for sensors, S2 and S3 is displayed in the Pi diagram in Fig. 5. The selectivity of ethanol, acetone, and LPG is 55%, 28.1%, and 16.9% respectively for the S3 sensor. Sensor S2is found to be 49.7%, 37.9 and 12.4% for ethanol, acetone, and LPG, respectively. It is clear from Fig. 5, thatethanol is more selectivethan liquified petroleum gas and acetone.
3.2.3. Transient response:
The transient response of the deposited thick films is studied in two terms the first is the response time and the second is the recovery time. First, the response time is the time required for the sensor to reach 90% of its total response to a signal such as resistance in contact with the target gas. Generally, the recovery is that time, taken by the sensor to return to the initial value after the phase of the measured variable has been removed. (Satterthwaite et al 2019, Vishwakarma et al 2021). Typically, the time to fall to 10% of the final value of the measured variable after phase removal is specified. The response and recovery times of sensors S1 and S3 are depicted in Fig. 6(a–c). Figure 6 (a) showed that the response times to ethanol gas are 55 s and 41 s, with recovery times of 150 and 125 s for the S1 and S3 sensors. The transient times of acetone gas are 69s/167s and 59s/160s for the S1 and S3 sensors as shown in Fig. 6(b). Also, Fig. 6(c) shows the transient time of LPG and it is 88s/207s and 79s/185s for S1 and S3.
3.2.4. Sensing mechanism:
SnO2 is a surface-controller sensing device. When test gases are expose to air oxygen molecules adsorbed on the surface of SnO2 and capture electron from conduction band of SnO2 to gives chemisorbed oxygen species as O-, O-2, O2- at operating temperature. When oxygen ions adsorbed on the surface reach saturation, the surface of the particles forms an electron depletion layer (Vishwakarma et al. 2023). The chemisorption reaction is O2- + e- → 2O- (at 150 0C to 400 0C). In addition, as ethanol gas contacts with the surface of the PbO-SnO2 gas-sensing element, oxygen ions react with ethanol as follows (Xu et al 2021): (also shown in Fig. 7)
C3H5OH + 8O- → 3H2O + 3CO2 + 8e- (3)
Since SnO2 is an n-type materials and they have major charge carrier’s electrons. The electrons captured by the oxygen ions are released back into the SnO2 particles, with some of the holes becoming inactive. Eventually, the electron depletion layer becomes thinner, and the electron concentration increases causing the resistance of the gas device to decrease. At 200 0C working temperature, electron carriers can easily move to the conduction band. Furthermore, more oxygen vacancies may provide additional adsorption sites. When more oxygen ions can react with ethanol, the sensing response of the PbO-SnO2 film becomes much better at 200 0C operating temperature.
Three types of sensors undoped SnO2 (S1) and 1wt% PbO-doped SnO2 (S2, S3) have been fabricated and its microstructural and gas sensing behaviors have been studied. Microstructural properties are studied using XRD and AFM techniques. The sensing performance such as sensing response, selectivity, transient time and sensing mechanism are reported. We observed that the maximum response to ethanol at 200 0C was found to be 88% for sensor S3 and the transient time was 65 s/129 s. Sensor S3 has been shown to respond faster, more sensitive (88%) and highly selective (55%) to ethanol than to LPG and acetone. Thus, the reported paper PbO-SnO2 is potentially used as an ethanol gas sensing device at 200 0C.
S1
Undoped SnO2
S2
1wt % PdO doped SnO2 (800 0C)
S3
1 wt % PdO doped SnO2 (900 0C)
AFM
Atomic ForceMicroscope
XRD
X-ray Diffraction
Acknowledgments: The first author is grateful to DSMNRU Lucknow for providing the UPDF in deportment of Physics. We are grateful to the Department of Physics, D.D.U. Gorakhpur University, Gorakhpur for providing the experimental facility for the measurement of gas sensing properties.
Ethical Approval: In this work, the authors are demonstrating that they have followed the accepted ethical standards of an actual research study.
Consent to participate: Credit does not in any way change the journal's criteria to qualify for authorship.
Consent to Publish: In this paper, some photographs, Figures, and tables are included in detail within the text to be published in Journal.
Authors' Contributions: All authors gave consent and contributed their work to the manuscript. Dr. Ankit Kumar Vishwakarma and Mr. Ajay Kumar Sharma did practical work under the direction of Dr. Lallan Yadav. A K Vishwakarma collects data and statistics and prepares a research paper appropriately. Dr. S. Srivastava, and Dr. Nutan Sharma presented some relevant principles in the introduction section. Dr AK Mishra removes grammatical errors and makes some corrections in the manuscript.
Funding: There are no funding agencies in this work.
Competing Interests: The authors declare that they have no competing interests or personal relationships that would influence the work reported in this paper. All authors agree that the author list and order is correct.
Availability of data and materials: Data will be available for your request.
- Asaithambi S, Sakthivel P, Karuppaiah M, Balamurugan K, Yuvak RK, Thambidurai M, Ravi G (2021) J Alloys Compd 853:157060
- Bhatia S, Verma N (2017) BediR. K., Results in Physics, 7: 801–806
- Divya J, Pramoth AK, Gnanamuthu SJ, Victoria DCB, Prabakar PCJ (2020) Phys B 588:412169
- Gao Y, Hou Q, Liu Q (2020) Solid State Communication 305:113764
- Hyun SK, Sun GJ, Lee JK, Lee C (2017), In Lee W., Woo Kim H. Ethanol gas sensing using a networked PbO-decorated SnO2 nanowire, Thin Solid Films, 637:21–26
- Kumar S (2020) Vacuum, 182:109725
- MaekawaT.,TamakiJ, Miura N, Yamazoe N (1992) Development of SnO2-based ethanol gas sensor. Sens Actuators B: Chem 9:63–69
- Mohanapriya P, Segawa H, Watanabe K, Watanabe K, Samitsu S, Natarajan TS, Jaya NV, Ohashi N (2013) Sens Actuators B 188:872–878
- Nagirnyak SV, Lutz VA, Dontsova TA and., Astrelin IM (2016) Nanoscale Res Lett 11:343
- Robles-Aguila MJ, Luna-Lopez JA, Hernandez AD, de la Luz (2018) Martinez-Juarez J. Rabanal M. E., Crystals, 8:406
- Salame CT (2020) Technologies and Materials for Renewable Energy. Environ Sustain Energy Rep 6:1–3
- Satterthwaite PF, Eberle S, Nedelcu S, Roman C, Hierold C (2019) Transient and steady-state readout of nanowire gas sensors in the presence of low-frequency noise. Sens Actuators B 297:126674
- Sharma AK, Vishwakarma AK, Yadava L (2022) Microstructural properties of palladium-doped tin oxide thick film. Proceedings of the National Workshop on Recent Advances in Condensed Matter and High Energy Physics. Springer Proceedings in Physics, vol 278. Springer, Singapore. https://doi.org/10.1007/978-981-19-2592-4_14
- Sirohi K, Kumar S, Singh V, Chauhan N (2021) Materials Today: Proceedings,21:1991–1998
- SrivastavaJ. K., PandeyP., MishraV. N., DwivediR. Sensing Mechanism of Pd-doped SnO2 sensor for LPG detection,Solid State Sciences, 11:1602–1605
- Tan W, Ruan YuQ, Huang X X (2015) Design of SnO2-based highly sensitive ethanol gas sensor based on quasi molecular-cluster imprinting mechanism. Sens Actuators B: Chem 212:47–54
- Tharsika T, Thanihaichelvan M, Haseeb A.S.M.A, Akbar SA (2019) Highly Sensitive and Selective Ethanol Sensor Based on ZnO Nanorod on SnO2 Thin Film Fabricated by Spray Pyrolysis. Front Mater 6:122
- Trinh TT, Tu NH, Le HH, Ryu KY, Le KB, Pillai K, Yi J (2011) Sens Actuators B 152:73–81
- Vishwakarma AK, Yadava L (2021) Environ Sci Pollut Res 28:3920–3927
- Vishwakarma AK, Majid SS, Yadava L (2019) XANES analysis and structural properties of CdS-doped TiO2. Vacuum 165:239–245
- Vishwakarma AK, Yadava L (2018) Fabrication and characterization of CdS doped ZnO nano thick film. Vacuum 155:214–218
- Vishwakarma AK, Sharma AK, Yadav NK, Yadav L (2021) Vacuum, 191:11036
- Vishwakarma AK, Yadava L (2018) Detection of propanol gas using titanium dioxide-based thick film, IOP Conference Series: Materials Science and Engineering, 404:012020
- Vishwakarma AK, Shram AK, Yadav L (2021) Journal of Physics: Conference Series, 1921:012118
- Vishwakarma AK, Shram AK, Mishra AK, Yadav L (2023) A titanium dioxide-based thick film gas sensor for propanol. Mater Letters: X 17:100184
- Xu H, Xu J, Li H, Zhang W, Zhang Y, Zhai Z (2021) Highly sensitive ethanol and acetone gas sensors with reduced working temperature based on Sr-doped BiFeO3 nanomaterial. J Mater Res Technol 17:1955–1963
- Xu S, Li D, Guo J, Hu Y, Yang P (2021) J Phys Chem Solids 148:109763
- Yadava L, Verma R, Dwivedi R (2010) Sensing properties of CdS doped tin oxide thick film gas sensor. Sens Actuators B 144:37–42