Abstract

A novel electro-colorimetric gas sensing technique based on the catalytic metal nanoparticles decorated metal oxide nanostructures integrated with multiple quantum wells (MQWs) has been proposed. The working principle has been demonstrated by the sensing device derived from the composite consisting of In0.15Ga0.85N/GaN MQWs and Pt-functionalized In2O3 nanopushpins for the detection of hydrogen gas. The pronounced changes in emission as well as Raman scattering spectra of InGaN/GaN MQWs under different target gas concentrations clearly illustrate the feasibility of our newly designed composites for the derivative of contact-free, simple and highly sensitive gas sensors with optical detection

© 2012 OSA

1. Introduction

One-dimensional (1D) metal oxide nanostructures as gas sensing materials have been extensively investigated due to their superior response to chemical environment in sensitivity, selectivity, and stability [1,2]. In general, the gas sensing mechanism of most metal oxide (MO)-based sensors relies on the adsorption-induced transfer of electric charge at the surface upon exposure to target species [3,4]. Conductometric [5,6], potentiometric [7,8], and impedometric [9,10] measurements are usually carried out electrically to characterize the metal oxide-based sensors. However, there are disadvantages that have been found for electrically characterized gas sensors. In the case of widely used conductometric technique, one of the drawbacks is that the mobility of carriers and the thickness of the sensing materials play an important role on its sensitivity [5]. For the sensor using the approach of potentiometric field effect transistors (FETs), the fabrication of reliable contacts to the 1D nanostructure FETs devices is a crucial technical issue in the manufacturing process of FET sensors. Thus, it is desirable to develop an alternative route to simple, contact free, yet highly sensitive gas sensors using optical detection. Optical detection of hydrogen gas is also more preferable owing to its inherent safety free from sparking when compared with electrical sensors. The carbon free and cost effective hydrogen as an alternative energy source shows considerable promise due to the virtually unlimited supply from the Earth and relatively neutral impact on the environment. However, due to the wide flammable range (4–75%) in air at 1 atm pressure, reliable sensors capable of detecting low concentrations of H2 are a necessity. Most optical hydrogen sensors use the palladium (Pd) or MO thin films coated onto the tip or along the length of an optical fiber [11]. Recently, the Pd functionalized optical hydrogen sensor using architectures other than optical fibers have been reported. For example, the optical hydrogen sensor based on the palladium (Pd) functionalized vertical cavity surface emitting laser (VCSEL) has been proposed [12]. With the shift of the lasing wavelength, the sensors can provide a quantitative determination of the hydrogen gas concentration over the range of 0–4%. Besides, the Pd-based optical hydrogen sensor was made into a resonant antenna-enhanced single-particle plasmonic sensor to avoid any inhomogeneous broadening and statistical effects in sensors based on nanopartical ensembles [13]. A redshift of ~5 nm of resonant peak and a dramatically suppressed resonant intensity of the gold–antenna surface plasmon resonance response were reported at the hydrogen gas concentration of 1% quantitatively.

On the other hand, the hydrogen gas sensing properties of MO nanostructures have been widely investigated. Typically, optical hydrogen sensors using MO materials operate based on the measurement of the evanescent field interaction [14]. Fortuitously, the sensing mechanism of MO materials is essentially governed by the electron exchange between the adsorbed molecules and the sensing material, which can change the surface electric field of metal oxide nanostructures [7,15]. On the other hand, it is well known that the application of an external electric field perpendicular to the layers of quantum wells can significantly changes absorption and photoluminescence (PL) where variations of absorption coefficient and transition energy can be explained by the quantum confined Stark effect (QCSE) [16]. Following this line of thinking, we propose an electro-colorimetric gas sensing technique based on electric field modulated emission from multiple quantum wells (MQWs), where the electric fields are generated by the adsorption-induced transferred electric charges resulted from the surface reaction of metal oxides with sensing gas molecules put on top proximity of MQWs. Here, as a proof of concept, we present an intelligently designed composite consisting of platinum (Pt)-functionalized In2O3 nanopushpins and InGaN/GaN MQWs to demonstrate the electro-colorimetric gas sensing technique considered above. With functionalization by Pt nanoparticles, it was found that the sensitivity of the sensor could be greatly enhanced [17]. The underlying mechanism can be well understood by the fact that In2O3 nanopushpins furnish oxygen ions and have a strong ability to capture the target gas due to a large surface-to-volume ratio. The change in electric field near the surface of metal oxide nanostructures resulting from the reduction-oxidation (REDOX) reaction provides the external electric field applying onto the layers of MQWs; electrons and holes are then separated toward opposite sides of the layer, resulting in a reduction in the energy of confined electron-hole pairs. Thus, electro-colorimetric change in emission and Raman scattering spectra arising from the QCSE and converse piezoelectric effect [18], respectively, could be clearly observed. Therefore, our result shown here can open a possibility for the derivative of sensors with optical detection methods.

2. Experiment

The studied InGaN/GaN MQWs were prepared by metal-organic chemical vapor deposition. The active region consists of an undoped series of ten periods of 2-nm-thick In0.15Ga0.85N wells and 9-nm-thick GaN barriers grown on c-plane (0001) sapphire. There is a 3 μm n-GaN layer between sapphire and MQWs. An extra InGaN/GaN QWs with lower indium content was deposited between the n-GaN layer and the active region as pre-strained layers. The results of the excitation power dependent PL measurements showed that there is negligible built-in piezoelectric field remaining in the active MQWs layers grown on the pre-strained layers. The PL peak position of the MQWs remains unchanged with the increasing excitation power density (not shown here) [19]. It reveals that the strain-induced piezoelectric polarization of the InGaN/GaN MQW layers is substantially reduced by the insertion of prestrained layers after n-GaN layer growth. The MQWs layers with diminished built-in piezoelectric field are suitable for the study on the external field induced QCSE.

The In2O3 nanopushpins were synthesized in an improved chemical vapor deposition system. Five grams of high-purity indium (In) grains were used as the starting materials when a n-type (100) silicon wafer was used as a substrate. The temperature of the In source was set at 800 °C and the substrate was set at 400 °C as described in the previous report [20]. The In2O3 nanopushpins fabricated by this method have diameters varying from tens to hundreds of nanometers and length up to one micrometer depending on the growth time. The structural properties of In2O3 nanopushpins were revealed by transmission electron microscopy (TEM) investigations. Figure 1(a) and 1(b) exhibits the bright field TEM image of an In2O3 nanopushpin with an inset (in Fig. 1(b)) of the indexed diffraction pattern along In2O3 [001] zone axis by selected area diffraction (SAD) of the area marked by a dotted circle as shown in the image. Figure 1(c) also shows a high-resolution TEM (HRTEM) lattice image of the In2O3 nanopushpins. It appears that mono-crystalline In2O3 nanopushpins can be achieved by the vapor transport method. The presence of certain background signals in the SAD pattern is attributed to the insufficient reaction of In vapor and oxygen at low temperature (low thermal budget), and the reduced thermal energy ends up with lower crystallinity of In2O3 nanopushpins. A schematic configuration of InGaN/GaN MQWs structure with In2O3 nanopushpins is also shown in Fig. 1(d).

 

Fig. 1 (a) Bright field transmission electron microscopy (TEM) image of In2O3 nanopushpins. (b) Enlarged TEM image (a) of In2O3 nanopushpins. The inset shows the selected area diffraction (SAD) pattern. (c) High-resolution TEM (HRTEM) lattice image of the In2O3 nanopushpins. (d) Schematic diagram of InGaN/GaN multiple quantum wells (MQWs) structure with In2O3 nanopushpins.

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To prepare for the composite consisting of Pt-functionalized In2O3 nanopushpins and InGaN/GaN MQWs, the sample of In2O3 nanopushpins was immersed into ethanol solution and dispersed by an ultrasonic bath for 10 minutes. After ultrasonication, the suspended In2O3 nanopushpins in ethanol solution were dripped onto the MQWs by a micropipette and dried at 85 °C for 5 minutes using a hot plate. The sample was then decorated with Pt nanoparticles by a DC sputtering system (JEOL JFC-1600) working at 40 mA for 60 seconds. Three categories of samples were prepared including the first one (denoted as Pt-MO-QW) consisting of Pt- functionalized In2O3 nanopushpins and InGaN/GaN MQWs, the second one (denoted as MO-QW) consisting of In2O3 nanopushpins and InGaN/GaN MQWs, and the third one (denoted as QW) with bare InGaN/GaN MQWs. Finally, the sample was mounted in a chamber to serve as a hydrogen gas detector through monitoring its emission spectra. Before the detection process, the chamber was filled with nitrogen, which served as the background gas, and then the target hydrogen with different concentrations was injected. All optical detections were measured at room temperature. A JEOL JEM2010 transmission electron microscope (TEM) operated at 200 kV was employed to characterize the structural properties of In2O3 nanopushpins. In2O3 nanopushpins were carried by a Cu-holder with meshes for TEM observations. Micro-photoluminescence (μ-PL) measurements were taken by a Jobin Yvon TRIAX-320 spectral system with an OLYMPUS microscope, and the optical source is provided by a solid state laser working at 374 nm. Micro-Raman (μ-Raman) scattering spectra were performed by a Jobin Yvon SPEC-T64000 spectral system with an OLYMPUS microscope, and the optical source is provided by an Ar+ laser working at 514 nm.

3. Results and discussion

In order to manifest the electro-colorimetric gas sensing technique based on electric field modulated emission from MQWs, the hydrogen sensing properties of the fabricated sensors based on the MQWs-integrated In2O3 nanopushpins with or without the Pt-functionalization and bare MQWs sample, were compared. Figures 2(a) -2(c) show the results of PL measurement at various hydrogen gas concentrations. As shown in Fig. 2(c), we can see that the PL peak position for the sample containing only InGaN/GaN MQWs shows no discernible shift with the increasing concentration of target hydrogen gas from 100 to 3000 ppm. The PL peak located near 2.74 eV can be referred to the excitonic emission of InGaN/GaN MQWs [18,19]. As shown in Figs. 2(a) and 2(b), the PL peak position for the Pt-MO-QW and MO-QW samples exhibits a red-shift with increasing concentration of target hydrogen gas, indicating that In2O3 metal oxide nanopushpins are the key material responsible for the red-shift in emission from MQWs, regardless of the Pt-functionalization. Figure 2(d) shows the evolution of the peak positions of PL spectra from these three samples as function of the concentration of the target hydrogen gas. Obviously, we can see that the response of Pt-MO-QW sample is stronger than that of the MO-QW sample while the QW sample exhibits almost no noticeable behavior. The red-shift in PL peak energy was found to be −12.1 and −21.0 meV at hydrogen concentration of 3000 ppm for the MO-QW and Pt-MO-QW sensors, respectively, compared with the emission peak energy of the bare MQWs. The red-shifted PL emission of the MQWs during the hydrogen sensing indicates the reduction in transition energy through the QCSE, where QCSE results from a shift in the excitonic energy level associated with an electric field across the QWs [16]. Thus, the fact of the different red-shifts in PL peak energy for the MO-QW and Pt-MO-QW samples is consequently related to the sensing mechanism.

 

Fig. 2 (a) Photoluminescence (PL) spectra of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins, (b) InGaN/GaN MQWs with In2O3 nanopushpins, and (c) InGaN/GaN MQWs under different concentrations of target hydrogen gas. (d) PL peak energy of the spectra in (a), (b), and (c) as function of the concentration of target hydrogen gas.

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The underlying mechanism of the detection may be preliminarily attributed to the electric field modulated emission from MQWs, where the electric fields are generated by the electric charge transfer process resulted from the surface reaction of metal-oxides with sensing gas molecules in close proximity on top of MQWs [7,15]. It is well accepted that the gas sensing abilities of semiconducting metal oxides can be attributed to the chemisorptions of oxygen species, such as O2-, O-, and O2-, on the oxide surface and the subsequent reaction between the adsorbed oxygen species and the target gas [310]. The REDOX reaction causes a change in the electric charge of metal oxide, which will alter the electric field nearby. If the metal oxide materials were on top proximity of MQWs, the altered electric charge of the sensing metal oxides will provide an external electric field applying onto the layers of MQWs, the photogenerated electrons and holes are then separated toward opposite sides of the layer, resulting in a reduction in the energy of confined electron-hole pairs. As a result, the PL emission exhibits a red-shift by QCSE as evidenced by the red-shift in PL peak energy of the Pt-MO-QW and MO-QW samples with the increasing concentration of target hydrogen gas as shown in Figs. 2(a), 2(b), and 2(d). Accordingly, the fact that In2O3 nanopushpins furnish oxygen ions to react with the target gas and offer a high surface to volume ratio to enhance the sensing response can be understood. On the other hand, hydrogen molecules are able to be dissociated into hydrogen atoms by the catalytic Pt metal and hence reinforcing the reaction rate [21]. Thus, the red-shift in PL peak energy of the Pt-functionalized In2O3 nanopushpins is much larger than that of the bare In2O3 nanopushpins, suggesting that the Pt-functionalization significantly assists the chemisorptions of oxygen species on the surface and the extent of change in surface electric field of In2O3 nanopushpins. The stronger response of the Pt-MO-QWs sample than that of the MO-QW sample shown in Fig. 2 therefore can be reasonably explained. Consequently, the difference in red-shifts in PL peak energy from the Pt-MO-QW and MO-QW samples further confirms the validation of electro-colorimetric gas sensing technique based on electric field modulated emission from MQWs integrated with the metal oxide nanostructures.

To further confirm the above explication, we have performed μ-Raman scattering measurements for all of the three samples under different concentrations of target hydrogen gas as shown in Figs. 3(a) -3(c). The broadened line located near 732 cm−1 can be assigned to InGaN A1(LO) mode [18]. Our results show a clear high-frequency shift in the peak position of the InGaN A1(LO) phonon line for the Pt-MO-QW and MO-QW samples with the increasing concentration of hydrogen gas. Figure 3(d) shows the evolution of the peak positions of Raman spectra from the three samples as function of the concentration of the target hydrogen gas. Similar to the behavior of PL spectra, we can see that the response of Pt-MO-QW sample is much more pronounced than that of the MO-QW sample while the QW sample exhibits almost no noticeable variation. A blue-shift in the frequency of the LO phonon in a noncentrosymmetric crystal is expected if the strength of the macroscopic electric field associated with the LO phonons is increased [22]. Here, the modification of the external electric field arises from the REDOX reaction between the oxygen species on the surface of In2O3 nanopushpins and the target hydrogen gas as described above. In view of the piezoelectric properties of InGaN/GaN MQWs, the electric field can be related to the resulting strain on the basis of the converse piezoelectric effect [18]. A change in electric field across the lattice can produce a strain and alter the lattice constant, which then leads to the variations of the Raman scattering spectra. Based on the same scenario for the effect of alteration of surface electric field of the sensing metal oxides on the PL spectra as shown in Fig. 2, the blue-shift in the frequency of the LO phonon from MQWs with increasing hydrogen concentration can be understood. According to the PL spectra shown in Figs. 2(a) and 2(b), the electric field across MQWs is increased by REDOX reaction, and therefore a high-frequency shift of the LO phonon energy can be expected. Likewise, the strain produced by the electric field across the InGaN/GaN MQWs of the Pt-MO-QW sample increases more than those of the two reference samples as expected. We therefore can see that the shifts in both electro-colorimetric change in emission and Raman scattering spectra of the sensing composites can be well explained in a consistent way based on the QCSE and piezoelectric alteration due to the REDOX reaction.

 

Fig. 3 (a) Raman scattering spectra of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins, (b) InGaN/GaN MQWs with In2O3 nanopushpins, and (c) InGaN/GaN MQWs under different concentrations of target hydrogen gas. (d) Raman peak position of the spectra in (a), (b), and (c) as function of the concentration of target hydrogen gas.

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In order to further understand the corresponding sensitivity of the electro-colorimetric gas sensing technique based on the MQWs-integrated In2O3 nanopushpins with or without the Pt-functionalization, the sensor response were analyzed by a model based on the Langmuir isotherm theory [23]. Figure 4 shows the responses of the sensor in terms of wavelength shift as a function of hydrogen gas concentrations. We observe that both responses of the two different sensors tended to saturate when the hydrogen gas concentration went up. This saturation behavior indicates that the adsorption sites responsible for adsorption-induced transfer of electric charge at the surface upon exposure to target species are fully occupied. The symbols in Fig. 4 are experimental data and the solid line is the best fit to the Langmuir isotherm. If we assume that the wavelength shift (△λ) is proportional to the density of adsorbed hydrogen gas and the surface coverage of adsorbed molecules follows Langmuir isotherm, the responses of the sensor in terms of wavelength shift can be written as: Δλ=ΔλmaxC/(K+C), where C and K are the hydrogen gas concentration and an equilibrium constant, respectively, △λmax is the maximum wavelength shift corresponding to the saturation of surface coverage. From the fitting results with correlation coefficients (R2) in the range of 0.97–0.99, the obtained values of △λmax and K for the Pt-MO-QW and MO-QW samples are 2.85 nm, 310 ppm and 1.67 nm, 240 ppm, respectively. The close correspondence between the fitting model and data allows an estimation of the detection limits of the gas sensing techniques. For the colorimetric sensors, the sensing with wavelength shift corresponding to the spectral resolution of the experimental set-up, 0.06 nm (1200 grooves/mm grating), is achievable. Accordingly, an interpolation of the sensitivity curves to a wavelength shift of 0.06 nm leads to the detection limits of 6.6 ppm and 9.0 ppm for the Pt-MO-QW and MO-QW samples, respectively. Thus, the Pt-functionalized In2O3 nanopushpins is more sensitive for hydrogen gas detection than the bare In2O3 nanopushpins, it confirms that the use of catalytic Pt coatings on In2O3 nanopushpins can enhance the detection sensitivity for hydrogen gas as reported in literature [17]. The detection limits of our technique presented here are comparable with the values reported previously [6].

 

Fig. 4 The wavelength shift as a function of hydrogen gas concentrations of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins and InGaN/GaN MQWs with In2O3 nanopushpins. The solid curves represent the best fits to a Langmuir isotherm.

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Finally, it is interesting to mention that, in addition to the wavelength shift in PL spectra and the wave-number shift in Raman spectra, the response of the colorimetric sensor proposed here can also be depicted in terms of the intensity change of PL spectra. According to the PL spectra shown in Figs. 2(a) and 2(b), the electric field across MQWs is increased by REDOX reaction, and hence the associated QCSE reduces the overlap between the electron and hole wave functions and results in the reduction of the PL intensity [18]. In order to illustrate the reproducible response of this sensing technique, a typical temporal response of PL peak intensity of the InGaN/GaN MQWs with In2O3 nanopushpins for one on-off cycle upon exposure to 3000 ppm hydrogen gas measured at room temperature is shown in Fig. 5 . It can be seen that the sample presents a reversible response to hydrogen gas which indicates a stable and reversible operation of gas sensing. The response time and recovery time are 330 s and 205 s, respectively, which are much longer than the measuring time of PL and Raman measurements. It is worth noting that the InGaN/GaN MQWs with In2O3 nanopushpins sample shows an obvious response to hydrogen gas even at room temperature (~300 K). The data also shows the repeatability of our designed gas sensors. However, further detailed research to investigate the composite hydrogen gas sensing technique proposed in this work with optimized density of In2O3 nanopushpins and long term sensor reliability should be conducted for the practical application of gas detection technology.

 

Fig. 5 Temporal response of PL peak intensity of the InGaN/GaN multiple quantum wells with In2O3 nanopushpins for one on-off cycle upon exposure to 3000 ppm hydrogen gas measured at room temperature.

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4. Summary

In summary, we have demonstrated the electric field modulated emission of InGaN/GaN MQWs integrated with Pt-functionalized In2O3 nanostructures can be used to sensitively detect hydrogen gas. The underlying mechanism is based on the highly sensitive nature of metal oxide nanostructures and piezoelectric property of nitride semiconductors to the ambient environment. In addition, the use of catalytic Pt nanoparticles further strengthens the sensing mechanism of the sensor based on the composite of metal oxide nanostructures and MQWs. Our working principle shown here proposes a feasible electro-colorimetric gas sensing technique using the MQWs integrated with metal oxide nanostructures functionalized by catalytic metal nanoparticles. In view of the wide utilization of LEDs and laser diodes based on nitride semiconductors, the study carried out along our guideline shown here should be very useful for the creation of highly sensitive sensors using optical detection.

Acknowledgments

This work was supported by the National Science Council and Ministry of Education of the Republic of China.

References and links

1. J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).

2. K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).

3. A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

4. C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

5. P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

6. A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

7. M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

8. C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

9. J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

10. Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

11. T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

12. B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

13. N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

14. H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

15. M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

16. Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

17. S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

18. T. Y. Lin, “Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 82(6), 880–882 (2003).

19. H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

20. C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

21. M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).

22. C. F. Klingshirn, Semiconductor Optics (Springer, Berlin, 1995).

23. D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

References

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  1. J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).
  2. K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).
  3. A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).
  4. C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).
  5. P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).
  6. A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).
  7. M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).
  8. C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).
  9. J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).
  10. Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).
  11. T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).
  12. B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).
  13. N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).
  14. H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).
  15. M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).
  16. Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).
  17. S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).
  18. T. Y. Lin, “Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 82(6), 880–882 (2003).
  19. H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).
  20. C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).
  21. M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).
  22. C. F. Klingshirn, Semiconductor Optics (Springer, Berlin, 1995).
  23. D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

2012 (3)

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

2011 (4)

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

2010 (2)

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).

2009 (3)

J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

2007 (1)

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

2006 (3)

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).

2005 (1)

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

2004 (1)

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

2003 (3)

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

T. Y. Lin, “Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 82(6), 880–882 (2003).

2002 (1)

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Alivisatos, A. P.

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Arbabi, A.

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

Banach, U.

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

Baratto, C.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Black, G.

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

Boon-Brett, L.

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

Chan, M. H.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

Chandrashekhar, M. V. S.

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

Chen, Y. F.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Chen, Y. T.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

Cheng, G. S.

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

Choi, K. J.

K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).

Choi, S. W.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Choquette, K. D.

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

Comini, E.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

El-Maghraby, E. M.

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

Faglia, G.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Feng, P.

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

Gao, S.

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

Giessen, H.

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Goddard, L. L.

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

Griffin, B. G.

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

Gu, H.

H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

Han, S.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Hentschel, M.

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Hsiai, T.

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Hu, Y.

H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

Huang, C. Y.

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Huang, J.

J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).

Hubert, T.

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

Jang, H. W.

K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).

Jho, Y. D.

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Jiang, C.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Kasten, A. M.

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

Kikuta, T.

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

Kim, D. S.

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Kim, H. S.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Kim, H. W.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Kim, S. S.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Koley, G.

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

Kolmakov, A.

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

Kumar, M. K.

M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).

Lei, B.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Li, C.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Li, J.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Lian, J. K.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

Liang, Q.

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

Lin, G. C.

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Lin, T. Y.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

T. Y. Lin, “Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 82(6), 880–882 (2003).

Liu, J.

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

Liu, N.

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Liu, X.

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Liu, X. L.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

Liu, Y. G.

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

Liu, Z. Q.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

Mao, S. X.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Moskovits, M.

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

Na, H. G.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Oh, E.

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Park, J. Y.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Park, S.

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

Qazi, M.

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

Qurashi, A.

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

Ramaprabhu, S.

M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).

Rouhanizadeh, M.

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Sberveglieri, G.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Shih, H. Y.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

Tang, M. L.

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Tang, T.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Vogt, T.

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

Wan, Q.

J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).

Wang, T. H.

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

Wang, Z.

H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

Wei, C. M.

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

Wei, Y.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Wu, N.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Wu, Y. J.

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Xu, H.

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

Xu, J.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Xue, X. Y.

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

Yahng, J. S.

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Yamazaki, T.

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

Yang, J. C.

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Yang, Y. J.

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Zappettini, A.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Zha, M.

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Zhang, D.

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Zhang, D. H.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

Zhang, Y. X.

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

Zhao, J.

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

Zhao, M.

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Zhou, C.

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

Zhou, C. W.

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

Adv. Mater. (Deerfield Beach Fla.) (1)

A. Kolmakov, Y. X. Zhang, G. S. Cheng, and M. Moskovits, “Detection of CO and O2 using tin oxide nanowire sensors,” Adv. Mater. (Deerfield Beach Fla.) 15(12), 997–1000 (2003).

Appl. Phys. Lett. (5)

P. Feng, X. Y. Xue, Y. G. Liu, and T. H. Wang, “Highly sensitive ethanol sensors based on {100}-bounded In2O3 nanocrystals due to face contact,” Appl. Phys. Lett. 89(24), 243514 (2006).

A. Qurashi, T. Yamazaki, E. M. El-Maghraby, and T. Kikuta, “Fabrication and gas sensing properties of In2O3 nanopushpins,” Appl. Phys. Lett. 95(15), 153109 (2009).

M. Qazi, G. Koley, S. Park, and T. Vogt, “NO2 detection by adsorption induced work function changes in In2O3 thin films,” Appl. Phys. Lett. 91(4), 043113 (2007).

C. Li, B. Lei, D. Zhang, X. Liu, S. Han, T. Tang, M. Rouhanizadeh, T. Hsiai, and C. Zhou, “Chemical gating of In2O3 nanowires by organic and biomolecules,” Appl. Phys. Lett. 83(19), 4014–4016 (2003).

T. Y. Lin, “Converse piezoelectric effect and photoelastic effect in InGaN/GaN multiple quantum wells,” Appl. Phys. Lett. 82(6), 880–882 (2003).

IEEE J. Quantum Electron. (1)

B. G. Griffin, A. Arbabi, A. M. Kasten, K. D. Choquette, and L. L. Goddard, “Hydrogen detection using a functionalized photonic crystal vertical cavity laser,” IEEE J. Quantum Electron. 48(2), 160–168 (2012).

J. Appl. Phys. (1)

M. Qazi, J. Liu, M. V. S. Chandrashekhar, and G. Koley, “Surface electronic property of SiC correlated with NO2 adsorption,” J. Appl. Phys. 106(9), 094901 (2009).

J. Phys. Chem. B (1)

M. K. Kumar and S. Ramaprabhu, “Nanostructured Pt functionlized multiwalled carbon nanotube based hydrogen sensor,” J. Phys. Chem. B 110(23), 11291–11298 (2006).

J. Phys. Chem. C (2)

H. Y. Shih, Y. T. Chen, C. M. Wei, M. H. Chan, J. K. Lian, Y. F. Chen, and T. Y. Lin, “Optical detection of glucose based on a composite consisting of enzymatic ZnO nanorods and InGaN/GaN multiple quantum wells,” J. Phys. Chem. C 115(30), 14664–14667 (2011).

C. Y. Huang, G. C. Lin, Y. J. Wu, T. Y. Lin, Y. J. Yang, and Y. F. Chen, “Efficient light harvesting by well-aligned In2O3 nanopushpins as antireflection layer on Si solar cells,” J. Phys. Chem. C 115(26), 13083–13087 (2011).

Nano Lett. (1)

D. H. Zhang, Z. Q. Liu, C. Li, T. Tang, X. L. Liu, S. Han, B. Lei, and C. W. Zhou, “Detection of NO2 down to ppb levels using individual and multiple In2O3 nanowire devices,” Nano Lett. 4(10), 1919–1924 (2004).

Nanotechnology (1)

S. S. Kim, J. Y. Park, S. W. Choi, H. S. Kim, H. G. Na, J. C. Yang, and H. W. Kim, “Significant enhancement of the sensing characteristics of In2O3 nanowires by functionalization with Pt nanoparticles,” Nanotechnology 21(41), 415502 (2010).

Nat. Mater. (1)

N. Liu, M. L. Tang, M. Hentschel, H. Giessen, and A. P. Alivisatos, “Nanoantenna-enhanced gas sensing in a single tailored nanofocus,” Nat. Mater. 10(8), 631–636 (2011).

Phys. Rev. B (1)

Y. D. Jho, J. S. Yahng, E. Oh, and D. S. Kim, “Field-dependent carrier decay dynamics in strained InxGa1-xN/GaN quantum wells,” Phys. Rev. B 66(3), 035334 (2002).

Sens. Actuators B Chem. (3)

Q. Liang, H. Xu, J. Zhao, and S. Gao, “Micro humidity sensors based on ZnO–In2O3 thin films with high performances,” Sens. Actuators B Chem. 165(1), 76–81 (2012).

T. Hubert, L. Boon-Brett, G. Black, and U. Banach, “Hydrogen sensors – A review,” Sens. Actuators B Chem. 157(2), 329–352 (2011).

C. Baratto, E. Comini, G. Faglia, G. Sberveglieri, M. Zha, and A. Zappettini, “Metal oxide nanocrystals for gas sensing,” Sens. Actuators B Chem. 109(1), 2–6 (2005).

Sensors (Basel Switzerland) (1)

H. Gu, Z. Wang, and Y. Hu, “Hydrogen gas sensors based on semiconductor oxide nanostructures,” Sensors (Basel Switzerland) 12(5), 5517–5550 (2012).

Sensors (Basel) (2)

J. Huang and Q. Wan, “Gas sensors based on semiconducting metal oxide one-dimensional nanostructures,” Sensors (Basel) 9(12), 9903–9924 (2009).

K. J. Choi and H. W. Jang, “One-dimensional oxide nanostructures as gas-sensing materials: review and issues,” Sensors (Basel) 10(4), 4083–4099 (2010).

Small (1)

J. Xu, N. Wu, C. Jiang, M. Zhao, J. Li, Y. Wei, and S. X. Mao, “Impedance characterization of ZnO nanobelt/Pd Schottky contacts in ammonia,” Small 2(12), 1458–1461 (2006).

Other (1)

C. F. Klingshirn, Semiconductor Optics (Springer, Berlin, 1995).

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Figures (5)

Fig. 1
Fig. 1

(a) Bright field transmission electron microscopy (TEM) image of In2O3 nanopushpins. (b) Enlarged TEM image (a) of In2O3 nanopushpins. The inset shows the selected area diffraction (SAD) pattern. (c) High-resolution TEM (HRTEM) lattice image of the In2O3 nanopushpins. (d) Schematic diagram of InGaN/GaN multiple quantum wells (MQWs) structure with In2O3 nanopushpins.

Fig. 2
Fig. 2

(a) Photoluminescence (PL) spectra of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins, (b) InGaN/GaN MQWs with In2O3 nanopushpins, and (c) InGaN/GaN MQWs under different concentrations of target hydrogen gas. (d) PL peak energy of the spectra in (a), (b), and (c) as function of the concentration of target hydrogen gas.

Fig. 3
Fig. 3

(a) Raman scattering spectra of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins, (b) InGaN/GaN MQWs with In2O3 nanopushpins, and (c) InGaN/GaN MQWs under different concentrations of target hydrogen gas. (d) Raman peak position of the spectra in (a), (b), and (c) as function of the concentration of target hydrogen gas.

Fig. 4
Fig. 4

The wavelength shift as a function of hydrogen gas concentrations of InGaN/GaN multiple quantum wells (MQWs) with Pt-functionalized In2O3 nanopushpins and InGaN/GaN MQWs with In2O3 nanopushpins. The solid curves represent the best fits to a Langmuir isotherm.

Fig. 5
Fig. 5

Temporal response of PL peak intensity of the InGaN/GaN multiple quantum wells with In2O3 nanopushpins for one on-off cycle upon exposure to 3000 ppm hydrogen gas measured at room temperature.

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