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Sputtered platinum thin films for resistive hydrogen sensor application
Author’s Accepted Manuscript Sputtered platinum thin films for resistive hydrogen sensor application Erdem Şennik, Şeyma Ürdem, Mustafa Erkovan, Necmettin Kılınç www.elsevier.com
PII: DOI: Reference:
S0167-577X(16)30636-X http://dx.doi.org/10.1016/j.matlet.2016.04.134 MLBLUE20731
To appear in: Materials Letters Received date: 14 March 2016 Accepted date: 17 April 2016 Cite this article as: Erdem Şennik, Şeyma Ürdem, Mustafa Erkovan and Necmettin Kılınç, Sputtered platinum thin films for resistive hydrogen sensor application, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.04.134 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Sputtered platinum thin films for resistive hydrogen sensor application Erdem Şennik1, Şeyma Ürdem2, Mustafa Erkovan2, Necmettin Kılınç1* 1
2
Nigde University, Nanotechnology Application and Research Center, 51245 Nigde, Turkey
Sakarya University, Department of Nanoscience and Nanoengineering, Sakarya, 54187, Turkey
* Corresponding author: Necmettin Kılınç (PhD), e-mail: [email protected]
Abstract This work presents hydrogen (H2) sensing properties of platinium (Pt) thin film deposited on glass substrate by sputter technique. The Pt thin films with different thickness prepared using RF sputtering method were characterized by the XRD, SEM and XPS techniques. Temperature dependent resistances and the gas measurements of the Pt thin films were investigated under a dry air flow at a temperature range from 30 °C to 200 °C. The H2 sensing properties of Pt thin film sensors were also examined in the concentration range of 0.1 % - 1 % H2. The results revealed that the Pt thin film with 2 nm thickness exhibited the best sensing performance to H2 at 30 °C under dry air flow. Keywords: Platinum, Thin film, Hydrogen sensor, Resistive sensor, Sputtering.
1. Introduction The detection of H2 in a wide range concentration is crucial for leak detection, safety issue and real time quantitative analysis [1-4]. Various types of H2 sensors have been extensively studied depending on physico-chemical detection mechanism such as catalytic, electrochemical, resistor based, work function based, mechanical, optical and acoustic. The resistor based hydrogen sensor could be divided into two parts as metallic resistor and semiconducting metal oxide resistor sensors. In general, palladium (Pd) and Pd alloy are used as sensitive materials for metallic resistor type hydrogen sensor [1-4]. Apart from Pd and Pd alloy, there are a few
1
numbers of publications about Pt resistive H2 sensor. Different types of Pt nanostructures such as thin film [5-7], nanoporous film [8, 9] and nanowire [10, 11] were fabricated for H2 sensor applications. All of these studies show that H2 sensing performance and mechanism of Pt nanostrucutures are needed much more effort to well understand. This study devoted that, Pt thin films were sputtered on the glass substrates and their H2 sensing properties were investigated depending on film thickness, temperature and concentration. 2. Experimental The Pt thin films (2-50 nm) were prepared using RF sputtering method on a glass slide. The films were coated with a constant RF power 50W at 5 mTorr argon pressure during deposition by using a NONOVAK 400 PVD system. The structural characterizations of the films were studied by Scanning Electron Microscopy (SEM, ZEISS EVO LS15), X-ray diffraction (XRD, Rigaku Smartlab diffractometer), and X-ray photoelectron spectrometer (XPS, Thermo 10 Scientific K-Alpha with monochromatic Al Kα radiation (1486.3 eV). Four Au pad electrodes were contacted on the top of Pt thin films for H2 gas sensing measurements. The changes of resistance for each film were recorded via a four point-probe connected to a multimeter (Agilent 34410A). The concentrations of H2 in high purity dry air were varied from 0.1% to 5%. Resistance-time characteristics of the sensors were measured by changing atmospheric conditions from 30 to 200 °C. The percentage sensitivity %, where Rg is the resistance exposed to the H2 and R0 is the baseline resistance under dry air, defined as: (1) 3. Results and Discussions SEM images, XRD and XPS patterns of Pt thin films are displayed in figure 1. All films are quite smooth and homogeneously covered on the glass surface. In figure 1d, the patterns show strong (111) and (200), and weak (200) and (131) reflections, which correspond to a face-
2
centered cubic crystalline structure [12-13]. Figure 1e shows that the peaks positions of Pt 4f7/2 and 4f5/2 were about 71.1eV and 74.5 eV correspond to pure Pt metallic state [14].
Figure 1: SEM images of Pt thin films with the thickness of (a) 2nm, (b) 5 nm, (c) 15 nm. XRD patterns for 50 nm Pt thin film (d) and XPS spectra of Pt4f for 5 nm Pt thin film (e).
The resistance-time graph of the 2nm and 5nm Pt thin film sensors under 1000ppm H2 at the indicated temperatures is given in figure 2a-b. After exposure to 1000ppm H2, the resistance of both the sensors decreased and then, the rate of decline reached saturation for all measured temperatures. During recovery with dry air, the resistance of the sensors increased rapidly and then come to saturation. The base line of both the sensors are shifted at 30 °C and 100 °C. But, both the sensors are fully reversible above 100 °C. The base line resistances of the sensors increased by enhancing the temperature due to the its metallic structure. Previously, Patel et al. investigated the structure and H2 response of the Pt film depending on temperature and H2 concentration [7]. They reported that exposure to ppm level of H2 in the presence of 5% oxygen with nitrogen as the carrier gas caused decreases in electrical resistance and the sensitivity of the film became more pronounced with increasing temperature. Yang et al. reported the performance of a single Pt nanowire for detecting H2 in air comparison with Pd nanowire [10]. Yoo et. al 3
investigated H2 gas sensing properties of the Pt nanowires and explained the sensing mechanism with reduced electron scattering in the cross section of the hydrogen adsorbed Pt nanowires [11].
Figure 2: The resistance-time graph for 2nm (a) and 5nm (b) Pt thin films exposed to 1000 ppm H2 at indicated temperatures. (c) A schematic diagram for H2 ad/absorbtion on Pt surface.
In our case, the sensing mechanism of Pt thin films could be explained as follow; Pt does not form a bulk hydride phase upon exposure to H2 such as Pd [7, 10, 11]. Hydrogen sensing mechanism is schematically given in figure 2c. The Pt surface covered with the absorbed oxygen atoms under dry air (figure 2c-1). Hydrogen atoms start to displace oxygen on the Pt surface during hydrogen exposing (figure 2c 2-3). After whole surface of the film covered with hydrogen, the number of charge carrier scattering at the Pt surface decreases. So, the decrease in the film resistance exposed to hydrogen could be related to decreasing the number of the surface charge carrier scattering. The ad/absorbsoption and desorption of hydrogen and oxygen in dry air from the film surface could be explained with some reactions [15-16]. When the molecular oxygen reacts with Pt surface in dry air, chemisorbed oxygen atoms form. If the atmosphere changes from dry air to molecular hydrogen, hydrogen atoms displace oxygen atoms on the Pt surface with catalytic formation of water and its desorption from the Pt surface. While the 4
chemisorbed hydrogen atoms on Pt surface react with dry air condition, oxygen atoms replace hydrogen atoms on the Pt surface with water formation. The replacement of the surface atoms (hydrogen or oxygen) is a reversible process. Temperature dependent sensitivities for 2nm and 5nm Pt thin film sensors against 1000 ppm H2 were given in figure 3a. The sensitivites of 2nm and 5nm Pt thin film sensors decreased from 2.7 and 0.7 to 1.1 and 0.3 with increasing temperature, respectively. The sensitivities of 2nm Pt thin film sensor is higher than the sensitivities of 5nm Pt thin film sensor for the measured temperature interval. So, the sensitivities of Pt thin films for H2 is strongly affected by the thickness of Pt film. Similarly, this behavior has been observed for Pt nanowire with different dimensions [10, 11]. The response time (t90) is defined as the times required for the change in the resistance variation level of 90% upon initiating the desired H2 concentration. Figure 3b shows the response time as a function of temperature for both 2nm and 5nm Pt thin film sensors. The response time of 2nm Pt thin film sensors is lower than that of 5nm Pt thin film sensor at room temperature and this behavior could be explained with a short diffusion path. But above the temperature of 100 °C the response time of the both sensors is approximately the same as shown in figure 3b. The response time is also decreased with increasing temperature for the both sensors and this behavior can be explained with a faster diffusion of hydrogen at higher temperatures.
Figure 3: Temperature dependent sensitivities (a) and respose time versus temperature (b) for both 2nm and 5nm Pt thin film sensors exposed to 1000ppm H2. 5
To investigate concentration dependent H2 sensing properties, a measurement was performed at 150 °C for 2 nm Pt film sensor due to fully reversible and recovery properties that observed for 1000ppm H2 exposure. The resistance versus time for 2 nm Pt film sensor at 150 °C exposed to H2 concentration interval of 0.1% - 1% is shown in figure 4a. After exposure to every desired H2 concentration, the resistance of 2nm Pt thin film sensors decreased, the rate of decline reached saturation and then after cleaning with dry air, the resistance of the sensor increased rapidly to its base line. The change in the resistance is enhanced with increasing H2 concentration. The dependence of the sensitivity on the H2 concentration was nearly linear at low concentrations, and the sensitivity started to a decrease tendency for high concentrations above 1 % H2. The sensitivity % increased from 0.8 to 10.2 between 0.1 % H2 and 5 % H2 is shown in figure 4b.
Figure 4: The resistance versus time graph (a) and H2 concentration dependent the sensitivity graph (b) for 2 nm Pt thin film sensor at 150 °C.
Conclusions H2 sensing properties of Pt thin films were investigated at a temperature range from 30 °C to 200 °C. The resistances of the films were directly proportional with temperature. The H2 gas sensing measurement results revealed that the 2 nm Pt thin film sensor is the best sensing performance to H2 at 30 °C. The sensitivity decreased at high temperatures but the best response
6
time was obtained at high temperature with clear response-recovery, good stability. Pt thin film sensor could be potatially used for H2 leak detection.
Acknowledgement: This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with project number of 114M853.
References [1].
J.S. Noh, J.M. Lee, and W. Lee, Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection. Sensors 11 (2011) 825-851.
[2].
J. Lee, W. Shim, J.S. Noh, and W. Lee, Design Rules for Nanogap-Based Hydrogen Gas Sensors. Chemphyschem 13 (2012) 1395-1403.
[3].
T. Hubert, L. Boon-Brett, G. Black, and U. Banach, Hydrogen sensors - A review. Sensors and Actuators B-Chemical 157 (2011) 329-352.
[4].
N. Kilinc, Resistive Hydrogen Sensors Based on Nanostructured Metals and Metal Alloys. Nanoscience and Nanotechnology Letters 5 (2013) 825-841.
[5].
K. Tsukada, H. Inoue, F. Katayama, K. Sakai, T. Kiwa, Changes in Work Function and Electrical Resistance of Pt Thin Films in the Presence of Hydrogen Gas. Japanese Journal of Applied Physics 51 (2012).
[6].
K. Tsukada, K. Sakai, T. Kiwa, Electric Characteristics of a Loop in Which Two Junctions between a Catalytic Metal and a Noncatalytic Metal Are under Different Hydrogen Gas Concentrations. Applied Physics Express 5 (2012).
[7].
S.V. Patel, J.L. Gland, J.W. Schwank, Film structure and conductometric hydrogen-gassensing characteristics of ultrathin platinum films. Langmuir 15 (1999) 3307-3311.
7
[8].
A. Abburi, N. Abrams, W.J. Yeh, Synthesis of nanoporous platinum thin films and application as hydrogen sensor. Journal of Porous Materials 19 (2012) 543-549.
[9].
A. Abburi, W.J. Yeh, Temperature and Pore Size Dependence on the Sensitivity of a Hydrogen Sensor Based on Nanoporous Platinum Thin Films. IEEE Sensors Journal 12 (2012) 2625-2629.
[10].
F. Yang, K.C. Donavan, S.C. Kung, R.M. Penner, The Surface Scattering-Based Detection of Hydrogen in Air Using a Platinum Nanowire. Nano Letters 12 (2012) 29242930.
[11].
H.-W. Yoo, S.-Y. Cho, H.-J. Jeon, and H.-T. Jung, Well-Defined and High Resolution Pt Nanowire Arrays for a High Performance Hydrogen Sensor by a Surface Scattering Phenomenon. Analytical Chemistry 87 (2015) 1480-1484
[12].
I. Chang, S. Woo, M.H. Lee, J.H. Shim, Y. Piao, S.W. Cha, Characterization of porous Pt films deposited via sputtering. Applied Surface Science 282 (2013) 463-466.
[13].
A. Hecq, J.P. Delrue, M. Hecq, T. Robert, Sputtering deposition, XPS and X-ray diffraction characterization of hard nitrogen-platinum thin films. Journal of Materials Science 16 407-412.
[14].
J.F. Moulder, J. Chastain, Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data, Physical Electronics Division, Perkin-Elmer Corporation, 1992.
[15].
C. Sachs, M. Hildebrand, S. Völkening, J. Wintterlin, and G. Ertl, Spatiotemporal SelfOrganization in a Surface Reaction: From the Atomic to the Mesoscopic Scale. Science 293 (2001) 1635-1638.
[16].
J.L. Gland, G.B. Fisher, and E.B. Kollin, The hydrogen-oxygen reaction over the Pt(111) surface: Transient titration of adsorbed oxygen with hydrogen. Journal of Catalysis 77 (1982) 263-278.
8
Highlights Pt thin films fabricated by RF sputtering on glass substrates with various thicknesses. Structural and H2 sensing properties of Pt films were studied. 2nm Pd film exhibited the best sensing performance to H2 at 30 °C under dry air flow. The sensitivity of Pt film decreased with enhancing film thickness.
9
PII: DOI: Reference:
S0167-577X(16)30636-X http://dx.doi.org/10.1016/j.matlet.2016.04.134 MLBLUE20731
To appear in: Materials Letters Received date: 14 March 2016 Accepted date: 17 April 2016 Cite this article as: Erdem Şennik, Şeyma Ürdem, Mustafa Erkovan and Necmettin Kılınç, Sputtered platinum thin films for resistive hydrogen sensor application, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.04.134 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Sputtered platinum thin films for resistive hydrogen sensor application Erdem Şennik1, Şeyma Ürdem2, Mustafa Erkovan2, Necmettin Kılınç1* 1
2
Nigde University, Nanotechnology Application and Research Center, 51245 Nigde, Turkey
Sakarya University, Department of Nanoscience and Nanoengineering, Sakarya, 54187, Turkey
* Corresponding author: Necmettin Kılınç (PhD), e-mail: [email protected]
Abstract This work presents hydrogen (H2) sensing properties of platinium (Pt) thin film deposited on glass substrate by sputter technique. The Pt thin films with different thickness prepared using RF sputtering method were characterized by the XRD, SEM and XPS techniques. Temperature dependent resistances and the gas measurements of the Pt thin films were investigated under a dry air flow at a temperature range from 30 °C to 200 °C. The H2 sensing properties of Pt thin film sensors were also examined in the concentration range of 0.1 % - 1 % H2. The results revealed that the Pt thin film with 2 nm thickness exhibited the best sensing performance to H2 at 30 °C under dry air flow. Keywords: Platinum, Thin film, Hydrogen sensor, Resistive sensor, Sputtering.
1. Introduction The detection of H2 in a wide range concentration is crucial for leak detection, safety issue and real time quantitative analysis [1-4]. Various types of H2 sensors have been extensively studied depending on physico-chemical detection mechanism such as catalytic, electrochemical, resistor based, work function based, mechanical, optical and acoustic. The resistor based hydrogen sensor could be divided into two parts as metallic resistor and semiconducting metal oxide resistor sensors. In general, palladium (Pd) and Pd alloy are used as sensitive materials for metallic resistor type hydrogen sensor [1-4]. Apart from Pd and Pd alloy, there are a few
1
numbers of publications about Pt resistive H2 sensor. Different types of Pt nanostructures such as thin film [5-7], nanoporous film [8, 9] and nanowire [10, 11] were fabricated for H2 sensor applications. All of these studies show that H2 sensing performance and mechanism of Pt nanostrucutures are needed much more effort to well understand. This study devoted that, Pt thin films were sputtered on the glass substrates and their H2 sensing properties were investigated depending on film thickness, temperature and concentration. 2. Experimental The Pt thin films (2-50 nm) were prepared using RF sputtering method on a glass slide. The films were coated with a constant RF power 50W at 5 mTorr argon pressure during deposition by using a NONOVAK 400 PVD system. The structural characterizations of the films were studied by Scanning Electron Microscopy (SEM, ZEISS EVO LS15), X-ray diffraction (XRD, Rigaku Smartlab diffractometer), and X-ray photoelectron spectrometer (XPS, Thermo 10 Scientific K-Alpha with monochromatic Al Kα radiation (1486.3 eV). Four Au pad electrodes were contacted on the top of Pt thin films for H2 gas sensing measurements. The changes of resistance for each film were recorded via a four point-probe connected to a multimeter (Agilent 34410A). The concentrations of H2 in high purity dry air were varied from 0.1% to 5%. Resistance-time characteristics of the sensors were measured by changing atmospheric conditions from 30 to 200 °C. The percentage sensitivity %, where Rg is the resistance exposed to the H2 and R0 is the baseline resistance under dry air, defined as: (1) 3. Results and Discussions SEM images, XRD and XPS patterns of Pt thin films are displayed in figure 1. All films are quite smooth and homogeneously covered on the glass surface. In figure 1d, the patterns show strong (111) and (200), and weak (200) and (131) reflections, which correspond to a face-
2
centered cubic crystalline structure [12-13]. Figure 1e shows that the peaks positions of Pt 4f7/2 and 4f5/2 were about 71.1eV and 74.5 eV correspond to pure Pt metallic state [14].
Figure 1: SEM images of Pt thin films with the thickness of (a) 2nm, (b) 5 nm, (c) 15 nm. XRD patterns for 50 nm Pt thin film (d) and XPS spectra of Pt4f for 5 nm Pt thin film (e).
The resistance-time graph of the 2nm and 5nm Pt thin film sensors under 1000ppm H2 at the indicated temperatures is given in figure 2a-b. After exposure to 1000ppm H2, the resistance of both the sensors decreased and then, the rate of decline reached saturation for all measured temperatures. During recovery with dry air, the resistance of the sensors increased rapidly and then come to saturation. The base line of both the sensors are shifted at 30 °C and 100 °C. But, both the sensors are fully reversible above 100 °C. The base line resistances of the sensors increased by enhancing the temperature due to the its metallic structure. Previously, Patel et al. investigated the structure and H2 response of the Pt film depending on temperature and H2 concentration [7]. They reported that exposure to ppm level of H2 in the presence of 5% oxygen with nitrogen as the carrier gas caused decreases in electrical resistance and the sensitivity of the film became more pronounced with increasing temperature. Yang et al. reported the performance of a single Pt nanowire for detecting H2 in air comparison with Pd nanowire [10]. Yoo et. al 3
investigated H2 gas sensing properties of the Pt nanowires and explained the sensing mechanism with reduced electron scattering in the cross section of the hydrogen adsorbed Pt nanowires [11].
Figure 2: The resistance-time graph for 2nm (a) and 5nm (b) Pt thin films exposed to 1000 ppm H2 at indicated temperatures. (c) A schematic diagram for H2 ad/absorbtion on Pt surface.
In our case, the sensing mechanism of Pt thin films could be explained as follow; Pt does not form a bulk hydride phase upon exposure to H2 such as Pd [7, 10, 11]. Hydrogen sensing mechanism is schematically given in figure 2c. The Pt surface covered with the absorbed oxygen atoms under dry air (figure 2c-1). Hydrogen atoms start to displace oxygen on the Pt surface during hydrogen exposing (figure 2c 2-3). After whole surface of the film covered with hydrogen, the number of charge carrier scattering at the Pt surface decreases. So, the decrease in the film resistance exposed to hydrogen could be related to decreasing the number of the surface charge carrier scattering. The ad/absorbsoption and desorption of hydrogen and oxygen in dry air from the film surface could be explained with some reactions [15-16]. When the molecular oxygen reacts with Pt surface in dry air, chemisorbed oxygen atoms form. If the atmosphere changes from dry air to molecular hydrogen, hydrogen atoms displace oxygen atoms on the Pt surface with catalytic formation of water and its desorption from the Pt surface. While the 4
chemisorbed hydrogen atoms on Pt surface react with dry air condition, oxygen atoms replace hydrogen atoms on the Pt surface with water formation. The replacement of the surface atoms (hydrogen or oxygen) is a reversible process. Temperature dependent sensitivities for 2nm and 5nm Pt thin film sensors against 1000 ppm H2 were given in figure 3a. The sensitivites of 2nm and 5nm Pt thin film sensors decreased from 2.7 and 0.7 to 1.1 and 0.3 with increasing temperature, respectively. The sensitivities of 2nm Pt thin film sensor is higher than the sensitivities of 5nm Pt thin film sensor for the measured temperature interval. So, the sensitivities of Pt thin films for H2 is strongly affected by the thickness of Pt film. Similarly, this behavior has been observed for Pt nanowire with different dimensions [10, 11]. The response time (t90) is defined as the times required for the change in the resistance variation level of 90% upon initiating the desired H2 concentration. Figure 3b shows the response time as a function of temperature for both 2nm and 5nm Pt thin film sensors. The response time of 2nm Pt thin film sensors is lower than that of 5nm Pt thin film sensor at room temperature and this behavior could be explained with a short diffusion path. But above the temperature of 100 °C the response time of the both sensors is approximately the same as shown in figure 3b. The response time is also decreased with increasing temperature for the both sensors and this behavior can be explained with a faster diffusion of hydrogen at higher temperatures.
Figure 3: Temperature dependent sensitivities (a) and respose time versus temperature (b) for both 2nm and 5nm Pt thin film sensors exposed to 1000ppm H2. 5
To investigate concentration dependent H2 sensing properties, a measurement was performed at 150 °C for 2 nm Pt film sensor due to fully reversible and recovery properties that observed for 1000ppm H2 exposure. The resistance versus time for 2 nm Pt film sensor at 150 °C exposed to H2 concentration interval of 0.1% - 1% is shown in figure 4a. After exposure to every desired H2 concentration, the resistance of 2nm Pt thin film sensors decreased, the rate of decline reached saturation and then after cleaning with dry air, the resistance of the sensor increased rapidly to its base line. The change in the resistance is enhanced with increasing H2 concentration. The dependence of the sensitivity on the H2 concentration was nearly linear at low concentrations, and the sensitivity started to a decrease tendency for high concentrations above 1 % H2. The sensitivity % increased from 0.8 to 10.2 between 0.1 % H2 and 5 % H2 is shown in figure 4b.
Figure 4: The resistance versus time graph (a) and H2 concentration dependent the sensitivity graph (b) for 2 nm Pt thin film sensor at 150 °C.
Conclusions H2 sensing properties of Pt thin films were investigated at a temperature range from 30 °C to 200 °C. The resistances of the films were directly proportional with temperature. The H2 gas sensing measurement results revealed that the 2 nm Pt thin film sensor is the best sensing performance to H2 at 30 °C. The sensitivity decreased at high temperatures but the best response
6
time was obtained at high temperature with clear response-recovery, good stability. Pt thin film sensor could be potatially used for H2 leak detection.
Acknowledgement: This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with project number of 114M853.
References [1].
J.S. Noh, J.M. Lee, and W. Lee, Low-Dimensional Palladium Nanostructures for Fast and Reliable Hydrogen Gas Detection. Sensors 11 (2011) 825-851.
[2].
J. Lee, W. Shim, J.S. Noh, and W. Lee, Design Rules for Nanogap-Based Hydrogen Gas Sensors. Chemphyschem 13 (2012) 1395-1403.
[3].
T. Hubert, L. Boon-Brett, G. Black, and U. Banach, Hydrogen sensors - A review. Sensors and Actuators B-Chemical 157 (2011) 329-352.
[4].
N. Kilinc, Resistive Hydrogen Sensors Based on Nanostructured Metals and Metal Alloys. Nanoscience and Nanotechnology Letters 5 (2013) 825-841.
[5].
K. Tsukada, H. Inoue, F. Katayama, K. Sakai, T. Kiwa, Changes in Work Function and Electrical Resistance of Pt Thin Films in the Presence of Hydrogen Gas. Japanese Journal of Applied Physics 51 (2012).
[6].
K. Tsukada, K. Sakai, T. Kiwa, Electric Characteristics of a Loop in Which Two Junctions between a Catalytic Metal and a Noncatalytic Metal Are under Different Hydrogen Gas Concentrations. Applied Physics Express 5 (2012).
[7].
S.V. Patel, J.L. Gland, J.W. Schwank, Film structure and conductometric hydrogen-gassensing characteristics of ultrathin platinum films. Langmuir 15 (1999) 3307-3311.
7
[8].
A. Abburi, N. Abrams, W.J. Yeh, Synthesis of nanoporous platinum thin films and application as hydrogen sensor. Journal of Porous Materials 19 (2012) 543-549.
[9].
A. Abburi, W.J. Yeh, Temperature and Pore Size Dependence on the Sensitivity of a Hydrogen Sensor Based on Nanoporous Platinum Thin Films. IEEE Sensors Journal 12 (2012) 2625-2629.
[10].
F. Yang, K.C. Donavan, S.C. Kung, R.M. Penner, The Surface Scattering-Based Detection of Hydrogen in Air Using a Platinum Nanowire. Nano Letters 12 (2012) 29242930.
[11].
H.-W. Yoo, S.-Y. Cho, H.-J. Jeon, and H.-T. Jung, Well-Defined and High Resolution Pt Nanowire Arrays for a High Performance Hydrogen Sensor by a Surface Scattering Phenomenon. Analytical Chemistry 87 (2015) 1480-1484
[12].
I. Chang, S. Woo, M.H. Lee, J.H. Shim, Y. Piao, S.W. Cha, Characterization of porous Pt films deposited via sputtering. Applied Surface Science 282 (2013) 463-466.
[13].
A. Hecq, J.P. Delrue, M. Hecq, T. Robert, Sputtering deposition, XPS and X-ray diffraction characterization of hard nitrogen-platinum thin films. Journal of Materials Science 16 407-412.
[14].
J.F. Moulder, J. Chastain, Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data, Physical Electronics Division, Perkin-Elmer Corporation, 1992.
[15].
C. Sachs, M. Hildebrand, S. Völkening, J. Wintterlin, and G. Ertl, Spatiotemporal SelfOrganization in a Surface Reaction: From the Atomic to the Mesoscopic Scale. Science 293 (2001) 1635-1638.
[16].
J.L. Gland, G.B. Fisher, and E.B. Kollin, The hydrogen-oxygen reaction over the Pt(111) surface: Transient titration of adsorbed oxygen with hydrogen. Journal of Catalysis 77 (1982) 263-278.
8
Highlights Pt thin films fabricated by RF sputtering on glass substrates with various thicknesses. Structural and H2 sensing properties of Pt films were studied. 2nm Pd film exhibited the best sensing performance to H2 at 30 °C under dry air flow. The sensitivity of Pt film decreased with enhancing film thickness.
9