Temperature sensor based on composite film of vanadium complex (VO<sub>2</sub>(3-fl)) and CNT

Kh. S.  Karimov; M. Mahroof-Tahir; M. Saleem; M. Tariq Saeed Chani; A. Khan Niaz

doi:10.1088/1674-4926/36/7/073004

J. Semicond. > 2015, Volume 36 > Issue 7 > 073004

SEMICONDUCTOR MATERIALS

Temperature sensor based on composite film of vanadium complex (VO₂(3-fl)) and CNT

Kh. S. Karimov^{1, 2}, M. Mahroof-Tahir³, M. Saleem⁴, M. Tariq Saeed Chani⁵ and A. Khan Niaz¹

+ Author Affiliations

Corresponding author: M. Saleem, E-mail: msaleem108@hotmail.com; drsaleem@ymail.com

DOI: 10.1088/1674-4926/36/7/073004

Abstract: A vanadium complex (VO₂(3-fl)) and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VO₂(3-fl) and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC (100 Hz) resistances of the temperature sensor decreased quasi-linearly with increasing the temperature in the range of 25-80 ℃. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.

Key words: CNT, vanadium complex, film, temperature sensor, resistance

1. Introduction

Nowadays, there has been a rapid advancement in the development of the sensors for application in monitoring various parameters such as humidity, temperature and chemical gases. A number of sensors have been fabricated on the basis of vanadium oxides^{[1, 2, 3, 4, 5, 6]}. Vanadium oxide, VO $_{2}$ , shows a large reversible change of electric, magnetic and optical properties at temperatures around 68-70 C^{[7, 8, 9]}. Transition of VO $_{2}$ from semiconductor to metal is observed. At transition temperature the optical properties of vanadium dioxide are quickly changed: the optical transmission is decreased and reflectivity is increased. Due to this anomalous behavior, vanadium dioxide is an attractive material for smart windows for solar energy control, electrical and optical switches. Microstructure and crystallinity of the films affect the hysteresis of the transition. By the addition of transition metals such as niobium, molybdenum or tungsten, the transition temperature of vanadium dioxide of 68 may be decreased.

It was observed that^[10] VO $_{2}$ films demonstrate holographic storage and bit recording properties by using a near-infrared laser^[11]. Switching time of about 30 ns and writing energy of the order of a few mJ/cm $^{2}$ were reported^[12]. The vanadium dioxide is an interesting candidate for modern applications of active thin films in optical or electric^[13] switches as well.

Vanadium oxide is considered as an n-type semiconducting material^[7]. Due to the semiconducting properties, vanadium oxides and their complexes have been reported to be used in different kinds of sensors. The lamellar nature of vanadium oxide makes it possible to modulate the adsorption and conduction properties. The electrical conductivity of the vanadium oxides can be enhanced by the formation of oxygen vacancies. Therefore, it is important to introduce different metal based materials into existing technology, which may bring a considerable improvements in functionality and/or cost of organic electronics^[14].

Although the existence of CNTs and cementite nanowires in ancient engineering products was proved a few years ago^[15] but since their discovery in 1991, CNTs have been intensively investigated^[16]. Due to their unique electronic and mechanical properties, CNTs have proved very interesting for researchers. Depending on the orientation of graphene lattice with respect to the axis of the tube, CNTs are electronically classified as metallic, semiconducting, or small-gap semiconducting (SGS)^[17]. Various types of sensors have been fabricated and investigated on the basis of single-walled nanotubes (SWNTs)^{[18, 19, 20, 21]}, double-walled carbon nanotubes (DWNTs)^[22], and multi-walled carbon nanotubes (MWNTs)^[23].

The temperature dependent electrical transport in highly disordered multiwalled carbon nanotubes of large outer diameter (60 nm) was investigated by Friedman et al.^[24]. These nanotubes were fabricated by means of the chemical vapor deposition process. Kumar et al. also investigated the temperature and chemical sensitivity of carbon nanofilms made on diamond surface by high temperature surface modification followed by plasma treatment^[25]. The conductance of these amorphous nanofilms was found to be sensitive for temperature and exposure to vapors of different organic compounds.

Recently the flexible electronic sensors^{[26, 27, 28, 29, 30]} have become more attractive for researchers. Among these sensors, the flexible temperature sensors are very interesting due to their ability to improve the functionality of integrated bio-parameter monitoring systems such as the body temperature controlling systems. Sibinski et al.^[31] fabricated a miniaturized flexible temperature sensor based on polymer composite filled with multiwalled carbon nanotubes. This sensor did not show the tensometric effect that was very common for other carbon-polymer sensors. The temperature sensitivity of the sensor was around of 0.13%, K $^{-1}$ . Zaitsev et al.^[32] developed temperature sensor based on an array of carbon nanowires, and it was fabricated by a 30 keV Ga $^{+}$ focused ion beam on diamond substrate. The sensor shows increase of current with increase in temperature in the range from 40 to 140 . Saraiya et al.^[33] fabricated a low-temperature (10-300 K) resistance sensor based on CNTs, which were grown on nickel film by using the ion beam deposition technique. The results revealed that CNTs behave as semiconductors.

The surface-type CNTs film temperature sensors were designed, fabricated and investigated^[34]. Resistance of the sensors decreased as the temperature increased, i.e. resistance-temperature relationship had semiconductive behavior. The average temperature sensitivity of the samples was $-0.24$ % C^-1. It was fabricated and investigated the resistive-type temperature sensor based on vanadium complex (VO $_{2}$ (3-fl))^[35]. It was found that resistive-temperature relationships of the sensors showed exponential behavior. The resistance temperature coefficients of the sensors were in the range of -(3.2-3.6)%. It seems reasonable to investigate the temperature sensor based on vanadium complex VO $_{2}$ (3-fl) and CNT, having potential advantages of high sensitivity of the complex and lower resistance of the CNT temperature sensors. This paper reports the fabrication of surface-type resistive temperature sensor, employing the composite of vanadium complex VO $_{2}$ (3-fl) and CNT as an active sensing element.

2.Experimental procedure

The molecular structure of the vanadium complex is shown in . The VO $_{2}$ (3-fl) was obtained from Aldrich and used as received. Commercially available glass slides were used as substrates which were primarily cleaned. In the first stage, the silver electrodes were deposited in a co-planar structure on the glass substrates using the Edwards AUTO 306 vacuum evaporation technique. The pressure inside the chamber was maintained at 10 $^{-5}$ mbar. The thickness of the electrodes was 200 nm and the gap was 40 $\mu$ m. Commercially produced (Sun Nanotech Co Ltd., China) CNTs powder was used to make composite with VO $_{2}$ (3-fl). The diameter of multiwalled nanotubes (MWNTs) varied between 10-30 nm. 2.5 wt.% of CNT and 2.5 wt.% of VO $_{2}$ (3-fl) were mixed in benzol and deposited by drop casting on the pre-patterned Ag surface-type electrodes. The device was kept at room temperature for 10 h to let the moisture evaporate from the films. The composites' films thickness was in the range of 20-30 $\mu$ m. The width of the surface-type sample's films was in the range of 6-8 mm. The cross sectional view of the fabricated resistive type temperature sensor is shown in . For SEM measurements, the composite films were deposited on glass substrate. SEM micrographs of thin film of the composite were obtained from a Hitachi SU-1500 scanning electron microscope. SEM micrographs have been obtained at 4 K magnification (). As requisite for morphological study through SEM, initially thin film of the composite was made conductive by depositing a thin film of platinum-palladium (Pt-Pd) (thickness $\sim$ 20 nm) on it. A Hitachi E-1010 ion sputter was used for Pt-Pd thin film deposition. Morphological study showed that sizes of CNT particles were $\sim$ 100 nm.

Figure 1. Molecular structure of the vanadium complex VO

$_{2}$ (3-fl).

DownLoad: Full-Size Img PowerPoint

Figure 2. Cross sectional view of the fabricated resistive type temperature sensor.

DownLoad: Full-Size Img PowerPoint

Figure 3. SEM image of the VO

$_{2}$ (3-fl)-CNT film.

DownLoad: Full-Size Img PowerPoint

The temperature measurements were carried out in a self made chamber which has been designed and developed in our laboratory. Resistance measurements were carried out using a Digital HiTester 3256 and an ESCORT ELC-132A meter at DC and AC at frequency of 100 Hz, respectively. The temperature was measured by a multimeter FLUKE 87. The experimental error for the measurement of the temperature was equal to $\pm$ 1 and the accuracy of the electric resistance measurement was equal to $\pm$ 2% (it was estimated as described by Dally et al^[36]).

3.Results and discussion

shows DC resistance versus temperature relationships for Ag/VO $_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensor, and exhibits AC resistance versus temperature relationships for the same sensor. The AC measurements were made at 100 Hz frequency. The resistance of the sensor measured at DC and AC decreased quasi-linear with increasing the temperature in the range of 25-80 . The overall resistance of the sensor decreases in the range of 1.8-2.1 and 1.9-2.0 times for DC and AC voltages, respectively. The resistance temperature coefficient ( $S$ ) of the samples can be calculated by^[36]:

$S=\frac{1}{R_{\rm o}}\frac{\Delta R}{\Delta T} \times 100\% ,$

(1)

where

$R_{\rm o}$ ,

$\Delta R$ and

$\Delta T$ are initial values of the sensor's resistance, and changes in the resistance and temperature, respectively. It was found that the resistance temperature coefficients of the sensors were in the range of

$-(0.9$ -1.3)% and

$-(1.1$ -1.3)% at DC and AC voltages, respectively. The resistance temperature coefficients (

$S$ ) of the composite samples are lower than semiconductor thermistors, but they are much larger than the metals^[36].

Figure 4. Resistance versus temperature relationships for two Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at DC.

DownLoad: Full-Size Img PowerPoint

Figure 5. Resistance versus temperature relationships for two Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at AC (100 Hz).

DownLoad: Full-Size Img PowerPoint

Using a linear function^[37]:

$Y=kx+b.$

(2)

The relative resistance can be represented as:

$\frac{R}{R_{\rm o}}=kT+b,$

(3)

where

$R$ ,

$R_{\rm o}$ and

$k$ are resistance, initial resistance and temperature coefficient, respectively. The results of experimental (solid line) and simulated (dashed line) by using Equation (3) are plotted in Figure 6 and are observed to be in good agreement. The values of

$k$ and

$b$ , used in Equation (3) were

$-0.8$

$\times$ 10

$^{-2}$ and 1.15, respectively.

Figure 6. Simulated (dashed line) and experimental (solid line) relative resistance (at AC (100 Hz)) versus temperature relationships for Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensor.

DownLoad: Full-Size Img PowerPoint

The mechanism of conductivity in the VO $_{2}$ (3-fl)-CNT composite samples can be considered as transitions between spatially separated sites that can be attributed to the Percolation theory^{[38, 39]}. According to Percolation theory, the effective conductivity ( $\sigma$ ) of the samples can be calculated as:

$\sigma =\frac{1}{LZ},$

(4)

where

$L$ is a characteristic length which depends on the concentration of sites, and

$Z$ is the resistance of the path with the lowest average resistance. With an increase in temperature, the sample is heated that may cause the reduction of

$Z$ due to the generation of charge carriers, and an increase of their concentration and mobility. As a result, the conductivity of the VO

$_{2}$ (3-fl)-CNT samples increases and the resistance decreases with the increase of temperature accordingly, as is observed experimentally (Figures 4 and 5).

As experimental resistance-temperature ( and ) relationships for the Ag/VO $_{2}$ (3-fl)-CNT/Ag sensors are quasi-linear, they can be linearized easier by nonlinear op-amps^[40].

A comparison of the properties of VO $_{2}$ (3-fl)-CNT with VO $_{2}$ (3-fl)^[35] and CNT^[34] based sensors shows that the composite sensors have lower values of resistances and these can be changed by changing the ratio of VO $_{2}$ (3-fl) and CNT in the composite. On the other hand, the resistance temperature coefficients of the composite temperature sensors are lower than the sensors based on VO $_{2}$ (3-ft), but much larger than those of the sensors fabricated by use of CNT. The non-linearity of the resistance-temperature relationships of the composite temperature sensors is lower than that of the sensors based on VO $_{2}$ (3-fl). These properties of the VO $_{2}$ (3-fl)-CNT composite based temperature sensors are very important for practical applications.

4.Conclusions

The resistive-type temperature sensor based on a composite of vanadium complex (VO $_{2}$ (3-fl)) and CNT was fabricated by drop-casting. It was found that resistive-temperature relationships of the sensors showed quasi-linear behavior. The resistance temperature coefficients of the sensors were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltages, respectively. The mechanism of change of conductivity with change of the temperature in the VO $_{2}$ (3-fl)-CNT composite was considered as transitions between spatially separated sites that can be attributed to the Percolation theory: with an increase in temperature, an increase of the concentration and mobility of charge carriers takes place. Fabrication of the VO $_{2}$ (3-fl)-CNT composites allows one, firstly, to decrease the value of the sensor's resistance due to the higher conductivity of the CNT and, secondly, to decrease the non-linearity of the resistance-temperature relationships. These characters are important for practical applications of temperature sensors.

Acknowledgements

The authors are thankful to the GIK Institute of Engineering Sciences and Technology for its support of this work.

References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]

Fig. 1. Molecular structure of the vanadium complex VO

$_{2}$ (3-fl).

DownLoad: Full-Size Img PowerPoint

Fig. 2. Cross sectional view of the fabricated resistive type temperature sensor.

DownLoad: Full-Size Img PowerPoint

Fig. 3. SEM image of the VO

$_{2}$ (3-fl)-CNT film.

DownLoad: Full-Size Img PowerPoint

Fig. 4. Resistance versus temperature relationships for two Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at DC.

DownLoad: Full-Size Img PowerPoint

Fig. 5. Resistance versus temperature relationships for two Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at AC (100 Hz).

DownLoad: Full-Size Img PowerPoint

Fig. 6. Simulated (dashed line) and experimental (solid line) relative resistance (at AC (100 Hz)) versus temperature relationships for Ag/VO

$_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensor.

DownLoad: Full-Size Img PowerPoint

DownLoad: CSV

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]

1	Bulk GaN-based SAW resonators with high quality factors for wireless temperature sensor Hongrui Lv, Xianglong Shi, Yujie Ai, Zhe Liu, Defeng Lin, et al. Journal of Semiconductors, 2022, 43(11): 114101. doi: 10.1088/1674-4926/43/11/114101
2	High Curie temperature ferromagnetism and high hole mobility in tensile strained Mn-doped SiGe thin films Jianhua Zhao Journal of Semiconductors, 2020, 41(8): 080201. doi: 10.1088/1674-4926/41/8/080201
3	Ultrathin free-standing graphene oxide film based flexible touchless sensor Lin Liu, Yingyi Wang, Guanghui Li, Sujie Qin, Ting Zhang, et al. Journal of Semiconductors, 2018, 39(1): 013002. doi: 10.1088/1674-4926/39/1/013002
4	Substrate temperature dependent studies on properties of chemical spray pyrolysis deposited CdS thin films for solar cell applications Kiran Diwate, Amit Pawbake, Sachin Rondiya, Rupali Kulkarni, Ravi Waykar, et al. Journal of Semiconductors, 2017, 38(2): 023001. doi: 10.1088/1674-4926/38/2/023001
5	A simple chemical route to synthesize the umangite phase of copper selenide (Cu₃Se₂) thin film at room temperature Balasaheb M. Palve, Sandesh R. Jadkar, Habib M. Pathan Journal of Semiconductors, 2017, 38(6): 063003. doi: 10.1088/1674-4926/38/6/063003
6	A low-power CMOS smart temperature sensor for RFID application Liangbo Xie, Jiaxin Liu, Yao Wang, Guangjun Wen Journal of Semiconductors, 2014, 35(11): 115002. doi: 10.1088/1674-4926/35/11/115002
7	Resistive humidity sensor based on vanadium complex films Kh. S. Karimov, M. Saleem, M. Mahroof-Tahir, R. Akram, M.T. Saeed Chanee, et al. Journal of Semiconductors, 2014, 35(9): 094001. doi: 10.1088/1674-4926/35/9/094001
8	Giant magnetoresistance in a two-dimensional electron gas modulated by ferromagnetic and Schottky metal stripes Lu Jianduo, Xu Bin Journal of Semiconductors, 2012, 33(7): 074007. doi: 10.1088/1674-4926/33/7/074007
9	A nanostructured copper telluride thin film grown at room temperature by an electrodeposition method S. S. Dhasade, S. H. Han, V. J. Fulari Journal of Semiconductors, 2012, 33(9): 093002. doi: 10.1088/1674-4926/33/9/093002
10	Improvement of the field emission properties of carbon nanotubes by CNT/Fe₃O₄ composite electrophoretic deposition Zheng Longwu, Hu Liqin, Yang Fan, Guo Tailiang Journal of Semiconductors, 2011, 32(12): 126001. doi: 10.1088/1674-4926/32/12/126001
11	Effect of alkaline slurry on the electric character of the pattern Cu wafer Hu Yi, Liu Yuling, Liu Xiaoyan, He Yangang, Wang Liran, et al. Journal of Semiconductors, 2011, 32(7): 076002. doi: 10.1088/1674-4926/32/7/076002
12	Structural and optoelectronic properties of sprayed Sb:SnO₂ thin films: Effects of substrate temperature and nozzle-to-substrate distance A. R. Babar, S. S. Shinde, A. V. Moholkar, C. H. Bhosale, K. Y. Rajpure, et al. Journal of Semiconductors, 2011, 32(10): 102001. doi: 10.1088/1674-4926/32/10/102001
13	Novel closed-form resistance formulae for rectangular interconnects Chen Baojun, Tang Zhen'an, Yu Tiejun Journal of Semiconductors, 2011, 32(5): 054008. doi: 10.1088/1674-4926/32/5/054008
14	A novel closed-form resistance model for trapezoidal interconnects Chen Baojun, Tang Zhen'an, Yu Tiejun Journal of Semiconductors, 2010, 31(8): 084011. doi: 10.1088/1674-4926/31/8/084011
15	Temperature coefficients of grain boundary resistance variations in a ZnO/p-Si heterojunction Liu Bingce, Liu Cihui, Xu Jun, Yi Bo Journal of Semiconductors, 2010, 31(12): 122001. doi: 10.1088/1674-4926/31/12/122001
16	An MWCNT-doped SnO₂ thin film NO₂ gas sensor by RF reactive magnetron sputtering Lin Wei, Huang Shizhen, Chen Wenzhe Journal of Semiconductors, 2010, 31(2): 024006. doi: 10.1088/1674-4926/31/2/024006
17	A cross-coupled-structure-based temperature sensor with reduced process variation sensitivity Tie Meng, Cheng Xu Journal of Semiconductors, 2009, 30(4): 045002. doi: 10.1088/1674-4926/30/4/045002
18	An ultra-low-power CMOS temperature sensor for RFID applications Xu Conghui, Gao Peijun, Che Wenyi, Tan Xi, Yan Na , et al. Journal of Semiconductors, 2009, 30(4): 045003. doi: 10.1088/1674-4926/30/4/045003
19	Monotonous Linearity Varying Stratified Nanocrystalline Silicon Films and as p-i-n Layer in Thin Film Solar Cells Jin Fei, Zhang Weijia, Jia Shiliang, Ding Zhaochong, Yan Lanqin, et al. Chinese Journal of Semiconductors , 2007, 28(S1): 333-336.
20	Alloy Temperature Dependence of Offset Voltage and Ohmic Contact Resistance in Thin Base InGaP/GaAs HBTs Yang Wei, Liu Xunchun, Zhu Min, Wang Runmei, Shen Huajun, et al. Chinese Journal of Semiconductors , 2006, 27(5): 765-768.

1.	Afzal, U., Wang, K., Liang, J. et al. Chemical engineering for advanced flexible sensors: Novel carbon-metal oxide nanocomposites with superior multi-sensing behavior. Sensors and Actuators B: Chemical, 2025. doi:10.1016/j.snb.2025.137449
2.	Li, L., Xiao, W., Lu, L. et al. High-Linearity and High-Stability AgNPs Thin-Film Temperature Sensor and Microcrack Thin-Film Strain Gauge Based on Laser-Assisted Fabrication. IEEE Sensors Journal, 2025. doi:10.1109/JSEN.2025.3563269
3.	Dönges, I., Yadav, S., Trouillet, V. et al. Selective Synthesis of 3D Aligned VO2 and V2O5 Carbon Nanotube Hybrid Materials by Chemical Vapor Deposition. Chemistry - A European Journal, 2024, 30(64): e202402024. doi:10.1002/chem.202402024
4.	Koudoumas, E., Le, K.T., Vernardou, D. Recent advances of chemical vapor deposited thermochromic vanadium dioxide materials. Energy Nexus, 2023. doi:10.1016/j.nexus.2023.100237
5.	Elango, P.F.M., Kabir, S., Kechanda Prasanna, P. et al. Vanadium Dioxide-Based Miniaturized Thermal Sensors: Humidity Effects on Phase Change and Sensitivity. ACS Applied Electronic Materials, 2022, 4(11): 5456-5467. doi:10.1021/acsaelm.2c01110
6.	Veiskarami, A., Sardari, D., Malekie, S. et al. Computational prediction of electrical percolation threshold in polymer/graphene-based nanocomposites with finite element method. Journal of Polymer Engineering, 2022, 42(10): 936-945. doi:10.1515/polyeng-2022-0101
7.	Alvarez-Guerrero, S., Ordonez-Miranda, J., de Coss, R. et al. Effect of the Metal–Insulator Transition on the Thermoelectric Properties of Composites Based on Bi 0.5Sb 1.5Te 3 with VO 2 Nanoparticles. International Journal of Thermophysics, 2022, 43(6): 95. doi:10.1007/s10765-022-03022-z
8.	Xiao, G., Weng, H., Ge, L. et al. Application Status of Carbon Nanotubes in Fire Detection Sensors. Frontiers in Materials, 2020. doi:10.3389/fmats.2020.588521
9.	Chani, M.T.S., Khan, S.B. Applications of nanocomposites in humidity sensors and solar cells. Current Nanoscience, 2020, 16(4): 504-506. doi:10.2174/157341371604200622095240
10.	Chani, M.T.S., Karimov, K.S., Asiri, A.M. Carbon Nanotubes and Graphene Powder Based Multifunctional Pressure, Displacement and Gradient of Temperature Sensors. Semiconductors, 2020, 54(1): 85-90. doi:10.1134/S1063782620010170
11.	Chani, M.T.S., Karimov, K.S., Asiri, A.M. Carbon Nanotubes and Graphene Powder based Multifunctional Pressure, Displacement and Gradient of Temperature Sensors. Semiconductors, 2019, 53(12): 1622-1629. doi:10.1134/S106378261916019X
12.	Monea, B.F., Ionete, E.I., Spiridon, S.I. et al. Carbon nanotubes and carbon nanotube structures used for temperature measurement. Sensors (Switzerland), 2019, 19(11): 2464. doi:10.3390/s19112464
13.	Chani, M.T.S., Karimov, K.S., Khan, S.B. et al. Impedimetric humidity and temperature sensing properties of chitosan-CuMn 2 O 4 spinel nanocomposite. Ceramics International, 2019, 45(8): 10565-10571. doi:10.1016/j.ceramint.2019.02.122
14.	Chani, M.T.S., Karimov, K.S., Asiri, A.M. Impedimetric humidity and temperature sensing properties of the graphene–carbon nanotubes–silicone adhesive nanocomposite. Journal of Materials Science: Materials in Electronics, 2019, 30(7): 6419-6429. doi:10.1007/s10854-019-00945-6
15.	Riaz, M., Karimov, K.S., Nabi, J.-U. Temperature dependence of the resistance, impedance and capacitance of semitransparent PTB7-Th and PCBM sensor. International Journal of Modern Physics B, 2019, 33(12): 1950110. doi:10.1142/S0217979219501108
16.	Chong, Y.S., Yeoh, K.H., Leow, P.L. et al. Piezoresistive strain sensor array using polydimethylsiloxane-based conducting nanocomposites for electronic skin application. Sensor Review, 2018, 38(4): 494-500. doi:10.1108/SR-11-2017-0238
17.	Jang, S.-H., Park, Y.-L. Carbon nanotube-reinforced smart composites for sensing freezing temperature and deicing by self-heating. Nanomaterials and Nanotechnology, 2018. doi:10.1177/1847980418776473
18.	Khan, G.R., Ahmad, B. Effect of quantum confinement on thermoelectric properties of vanadium dioxide nanofilms. Applied Physics A: Materials Science and Processing, 2017, 123(12): 795. doi:10.1007/s00339-017-1363-x
19.	Song, S., Huang, Q., Zhu, W. Hydrothermal route to VO2 (B) nanorods: controlled synthesis and characterization. Journal of Nanoparticle Research, 2017, 19(10): 353. doi:10.1007/s11051-017-4051-z
20.	Chani, M.T.S.. Impedimetric sensing of temperature and humidity by using organic-inorganic nanocomposites composed of chitosan and a CuO-Fe3O4 nanopowder. Microchimica Acta, 2017, 184(7): 2349-2356. doi:10.1007/s00604-017-2259-3
21.	Karimov, K.S., Tahir, M.M., Saleem, M. et al. Vanadium Complex (VO2(3-fl)) Films Based Resistive Temperature Sensor. ARPN Journal of Engineering and Applied Sciences, 2017, 4(2): 6-9. doi:10.5455/jeas.2017110102
22.	Khan, G.R., Bhat, B.A. Quantum size effect across semiconductor-to-metal phase transition in vanadium dioxide thin films. Micro and Nano Letters, 2015, 10(11): 607-612. doi:10.1049/mnl.2015.0213

Search

GET CITATION

Kh. S. Karimov, M. Mahroof-Tahir, M. Saleem, M. Tariq Saeed Chani, A. Khan Niaz. Temperature sensor based on composite film of vanadium complex (VO₂(3-fl)) and CNT[J]. Journal of Semiconductors, 2015, 36(7): 073004. doi: 10.1088/1674-4926/36/7/073004

Kh. S. Karimov, M. Mahroof-Tahir, M. Saleem, M. T. S. Chani, A. K. Niaz. Temperature sensor based on composite film of vanadium complex (VO2(3-fl)) and CNT[J]. J. Semicond., 2015, 36(7): 073004. doi: 10.1088/1674-4926/36/7/073004.

Export: BibTex EndNote

Article Metrics

Article views: 2851 Times PDF downloads: 26 Times Cited by: 22 Times

History

Received: 20 December 2014 Revised: Online: Published: 01 July 2015

Article Navigation > Journal of Semiconductors > 2015 > 36(7): 073004

Kh. S. Karimov, M. Mahroof-Tahir, M. Saleem, M. Tariq Saeed Chani, A. Khan Niaz. Temperature sensor based on composite film of vanadium complex (VO2(3-fl)) and CNT[J]. Journal of Semiconductors, 2015, 36(7): 073004. doi: 10.1088/1674-4926/36/7/073004 ****Kh. S. Karimov, M. Mahroof-Tahir, M. Saleem, M. T. S. Chani, A. K. Niaz. Temperature sensor based on composite film of vanadium complex (VO2(3-fl)) and CNT[J]. J. Semicond., 2015, 36(7): 073004. doi: 10.1088/1674-4926/36/7/073004.

Citation:

PDF( 1315 KB)

Temperature sensor based on composite film of vanadium complex (VO₂(3-fl)) and CNT

DOI: 10.1088/1674-4926/36/7/073004

1.
GIK Institute of Engineering Sciences and Technology, Topi, District Swabi-23640, KPK, Pakistan
2.
Center for Innovative Development of Science and New Technologies, Academy of Sciences, Rudaki Ave.33, Dushanbe, 734025, Tajikistan
3.
Department of Chemistry and Earth Sciences, Qatar University, Doha-2713, Qatar
4.
Government College of Science, Wahdat Road, Lahore-54570, Pakistan
5.
Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, Jeddah 21589, Saudi Arabia

More Information

Corresponding author: E-mail: msaleem108@hotmail.com; drsaleem@ymail.com
Received Date: 2014-12-20
Accepted Date: 2015-01-31
Published Date: 2015-01-25

Abstract

Abstract

A vanadium complex (VO₂(3-fl)) and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VO₂(3-fl) and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC (100 Hz) resistances of the temperature sensor decreased quasi-linearly with increasing the temperature in the range of 25-80 ℃. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.
- CNT,
- vanadium complex,
- film,
- temperature sensor,
- resistance

FullText(HTML)

1. Introduction

Nowadays, there has been a rapid advancement in the development of the sensors for application in monitoring various parameters such as humidity, temperature and chemical gases. A number of sensors have been fabricated on the basis of vanadium oxides^{[1, 2, 3, 4, 5, 6]}. Vanadium oxide, VO $_{2}$ , shows a large reversible change of electric, magnetic and optical properties at temperatures around 68-70 C^{[7, 8, 9]}. Transition of VO $_{2}$ from semiconductor to metal is observed. At transition temperature the optical properties of vanadium dioxide are quickly changed: the optical transmission is decreased and reflectivity is increased. Due to this anomalous behavior, vanadium dioxide is an attractive material for smart windows for solar energy control, electrical and optical switches. Microstructure and crystallinity of the films affect the hysteresis of the transition. By the addition of transition metals such as niobium, molybdenum or tungsten, the transition temperature of vanadium dioxide of 68 may be decreased.

It was observed that^[10] VO $_{2}$ films demonstrate holographic storage and bit recording properties by using a near-infrared laser^[11]. Switching time of about 30 ns and writing energy of the order of a few mJ/cm $^{2}$ were reported^[12]. The vanadium dioxide is an interesting candidate for modern applications of active thin films in optical or electric^[13] switches as well.

Vanadium oxide is considered as an n-type semiconducting material^[7]. Due to the semiconducting properties, vanadium oxides and their complexes have been reported to be used in different kinds of sensors. The lamellar nature of vanadium oxide makes it possible to modulate the adsorption and conduction properties. The electrical conductivity of the vanadium oxides can be enhanced by the formation of oxygen vacancies. Therefore, it is important to introduce different metal based materials into existing technology, which may bring a considerable improvements in functionality and/or cost of organic electronics^[14].

Although the existence of CNTs and cementite nanowires in ancient engineering products was proved a few years ago^[15] but since their discovery in 1991, CNTs have been intensively investigated^[16]. Due to their unique electronic and mechanical properties, CNTs have proved very interesting for researchers. Depending on the orientation of graphene lattice with respect to the axis of the tube, CNTs are electronically classified as metallic, semiconducting, or small-gap semiconducting (SGS)^[17]. Various types of sensors have been fabricated and investigated on the basis of single-walled nanotubes (SWNTs)^{[18, 19, 20, 21]}, double-walled carbon nanotubes (DWNTs)^[22], and multi-walled carbon nanotubes (MWNTs)^[23].

The temperature dependent electrical transport in highly disordered multiwalled carbon nanotubes of large outer diameter (60 nm) was investigated by Friedman et al.^[24]. These nanotubes were fabricated by means of the chemical vapor deposition process. Kumar et al. also investigated the temperature and chemical sensitivity of carbon nanofilms made on diamond surface by high temperature surface modification followed by plasma treatment^[25]. The conductance of these amorphous nanofilms was found to be sensitive for temperature and exposure to vapors of different organic compounds.

Recently the flexible electronic sensors^{[26, 27, 28, 29, 30]} have become more attractive for researchers. Among these sensors, the flexible temperature sensors are very interesting due to their ability to improve the functionality of integrated bio-parameter monitoring systems such as the body temperature controlling systems. Sibinski et al.^[31] fabricated a miniaturized flexible temperature sensor based on polymer composite filled with multiwalled carbon nanotubes. This sensor did not show the tensometric effect that was very common for other carbon-polymer sensors. The temperature sensitivity of the sensor was around of 0.13%, K $^{-1}$ . Zaitsev et al.^[32] developed temperature sensor based on an array of carbon nanowires, and it was fabricated by a 30 keV Ga $^{+}$ focused ion beam on diamond substrate. The sensor shows increase of current with increase in temperature in the range from 40 to 140 . Saraiya et al.^[33] fabricated a low-temperature (10-300 K) resistance sensor based on CNTs, which were grown on nickel film by using the ion beam deposition technique. The results revealed that CNTs behave as semiconductors.

The surface-type CNTs film temperature sensors were designed, fabricated and investigated^[34]. Resistance of the sensors decreased as the temperature increased, i.e. resistance-temperature relationship had semiconductive behavior. The average temperature sensitivity of the samples was $-0.24$ % C^-1. It was fabricated and investigated the resistive-type temperature sensor based on vanadium complex (VO $_{2}$ (3-fl))^[35]. It was found that resistive-temperature relationships of the sensors showed exponential behavior. The resistance temperature coefficients of the sensors were in the range of -(3.2-3.6)%. It seems reasonable to investigate the temperature sensor based on vanadium complex VO $_{2}$ (3-fl) and CNT, having potential advantages of high sensitivity of the complex and lower resistance of the CNT temperature sensors. This paper reports the fabrication of surface-type resistive temperature sensor, employing the composite of vanadium complex VO $_{2}$ (3-fl) and CNT as an active sensing element.

2.Experimental procedure

The molecular structure of the vanadium complex is shown in . The VO $_{2}$ (3-fl) was obtained from Aldrich and used as received. Commercially available glass slides were used as substrates which were primarily cleaned. In the first stage, the silver electrodes were deposited in a co-planar structure on the glass substrates using the Edwards AUTO 306 vacuum evaporation technique. The pressure inside the chamber was maintained at 10 $^{-5}$ mbar. The thickness of the electrodes was 200 nm and the gap was 40 $\mu$ m. Commercially produced (Sun Nanotech Co Ltd., China) CNTs powder was used to make composite with VO $_{2}$ (3-fl). The diameter of multiwalled nanotubes (MWNTs) varied between 10-30 nm. 2.5 wt.% of CNT and 2.5 wt.% of VO $_{2}$ (3-fl) were mixed in benzol and deposited by drop casting on the pre-patterned Ag surface-type electrodes. The device was kept at room temperature for 10 h to let the moisture evaporate from the films. The composites' films thickness was in the range of 20-30 $\mu$ m. The width of the surface-type sample's films was in the range of 6-8 mm. The cross sectional view of the fabricated resistive type temperature sensor is shown in . For SEM measurements, the composite films were deposited on glass substrate. SEM micrographs of thin film of the composite were obtained from a Hitachi SU-1500 scanning electron microscope. SEM micrographs have been obtained at 4 K magnification (). As requisite for morphological study through SEM, initially thin film of the composite was made conductive by depositing a thin film of platinum-palladium (Pt-Pd) (thickness $\sim$ 20 nm) on it. A Hitachi E-1010 ion sputter was used for Pt-Pd thin film deposition. Morphological study showed that sizes of CNT particles were $\sim$ 100 nm.

Molecular structure of the vanadium complex VO $_{2}$ (3-fl).

DownLoad: Full-Size Img PowerPoint

Figure 2. Cross sectional view of the fabricated resistive type temperature sensor.

DownLoad: Full-Size Img PowerPoint

SEM image of the VO $_{2}$ (3-fl)-CNT film.

DownLoad: Full-Size Img PowerPoint

The temperature measurements were carried out in a self made chamber which has been designed and developed in our laboratory. Resistance measurements were carried out using a Digital HiTester 3256 and an ESCORT ELC-132A meter at DC and AC at frequency of 100 Hz, respectively. The temperature was measured by a multimeter FLUKE 87. The experimental error for the measurement of the temperature was equal to $\pm$ 1 and the accuracy of the electric resistance measurement was equal to $\pm$ 2% (it was estimated as described by Dally et al^[36]).

3.Results and discussion

shows DC resistance versus temperature relationships for Ag/VO $_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensor, and exhibits AC resistance versus temperature relationships for the same sensor. The AC measurements were made at 100 Hz frequency. The resistance of the sensor measured at DC and AC decreased quasi-linear with increasing the temperature in the range of 25-80 . The overall resistance of the sensor decreases in the range of 1.8-2.1 and 1.9-2.0 times for DC and AC voltages, respectively. The resistance temperature coefficient ( $S$ ) of the samples can be calculated by^[36]:
$S=\frac{1}{R_{\rm o}}\frac{\Delta R}{\Delta T} \times 100\% ,$ (1)
where $R_{\rm o}$ , $\Delta R$ and $\Delta T$ are initial values of the sensor's resistance, and changes in the resistance and temperature, respectively. It was found that the resistance temperature coefficients of the sensors were in the range of $-(0.9$ -1.3)% and $-(1.1$ -1.3)% at DC and AC voltages, respectively. The resistance temperature coefficients ( $S$ ) of the composite samples are lower than semiconductor thermistors, but they are much larger than the metals^[36].

Resistance versus temperature relationships for two Ag/VO $_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at DC.

DownLoad: Full-Size Img PowerPoint

Resistance versus temperature relationships for two Ag/VO $_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensors at AC (100 Hz).

DownLoad: Full-Size Img PowerPoint

Using a linear function^[37]:

$Y=kx+b.$ (2)

The relative resistance can be represented as:
$\frac{R}{R_{\rm o}}=kT+b,$ (3)
where $R$ , $R_{\rm o}$ and $k$ are resistance, initial resistance and temperature coefficient, respectively. The results of experimental (solid line) and simulated (dashed line) by using Equation (3) are plotted in and are observed to be in good agreement. The values of $k$ and $b$ , used in Equation (3) were $-0.8$ $\times$ 10 $^{-2}$ and 1.15, respectively.

Simulated (dashed line) and experimental (solid line) relative resistance (at AC (100 Hz)) versus temperature relationships for Ag/VO $_{2}$ (3-fl)-CNT/Ag surface-type resistive temperature sensor.

DownLoad: Full-Size Img PowerPoint

The mechanism of conductivity in the VO $_{2}$ (3-fl)-CNT composite samples can be considered as transitions between spatially separated sites that can be attributed to the Percolation theory^{[38, 39]}. According to Percolation theory, the effective conductivity ( $\sigma$ ) of the samples can be calculated as:
$\sigma =\frac{1}{LZ},$ (4)
where $L$ is a characteristic length which depends on the concentration of sites, and $Z$ is the resistance of the path with the lowest average resistance. With an increase in temperature, the sample is heated that may cause the reduction of $Z$ due to the generation of charge carriers, and an increase of their concentration and mobility. As a result, the conductivity of the VO $_{2}$ (3-fl)-CNT samples increases and the resistance decreases with the increase of temperature accordingly, as is observed experimentally (Figures 4 and 5).

As experimental resistance-temperature ( and ) relationships for the Ag/VO $_{2}$ (3-fl)-CNT/Ag sensors are quasi-linear, they can be linearized easier by nonlinear op-amps^[40].

A comparison of the properties of VO $_{2}$ (3-fl)-CNT with VO $_{2}$ (3-fl)^[35] and CNT^[34] based sensors shows that the composite sensors have lower values of resistances and these can be changed by changing the ratio of VO $_{2}$ (3-fl) and CNT in the composite. On the other hand, the resistance temperature coefficients of the composite temperature sensors are lower than the sensors based on VO $_{2}$ (3-ft), but much larger than those of the sensors fabricated by use of CNT. The non-linearity of the resistance-temperature relationships of the composite temperature sensors is lower than that of the sensors based on VO $_{2}$ (3-fl). These properties of the VO $_{2}$ (3-fl)-CNT composite based temperature sensors are very important for practical applications.

4.Conclusions

The resistive-type temperature sensor based on a composite of vanadium complex (VO $_{2}$ (3-fl)) and CNT was fabricated by drop-casting. It was found that resistive-temperature relationships of the sensors showed quasi-linear behavior. The resistance temperature coefficients of the sensors were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltages, respectively. The mechanism of change of conductivity with change of the temperature in the VO $_{2}$ (3-fl)-CNT composite was considered as transitions between spatially separated sites that can be attributed to the Percolation theory: with an increase in temperature, an increase of the concentration and mobility of charge carriers takes place. Fabrication of the VO $_{2}$ (3-fl)-CNT composites allows one, firstly, to decrease the value of the sensor's resistance due to the higher conductivity of the CNT and, secondly, to decrease the non-linearity of the resistance-temperature relationships. These characters are important for practical applications of temperature sensors.

Acknowledgements

The authors are thankful to the GIK Institute of Engineering Sciences and Technology for its support of this work.

References(40)

References

[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]