Effect of Post Deposition Annealing Process on the pH Sensitivity of Spin-Coated Titanium Dioxide Thin Film

Abstract:

This paper presents an investigation on titanium dioxide (TiO₂) thin film, which is used as sensing membrane for Extended-Gate Field Effect Transistor (EGFET) for pH sensing application. TiO₂ thin films were deposited using sol-gel spin coating method on indium tin oxide (ITO) substrates. After the deposition, the thin films were annealed at 300 °C for 10 and 15 min, while another sample was annealed at 400 °C for 15 min. The sensitivity measurement was taken using the EGFET setup equipment with constant-current (100 μA) and constant-voltage (0.5 V) biasing interfacing circuit. TiO₂ thin film as the pH-sensitive membrane and the working electrode was connected to a commercial metal-oxide semiconductor FET (MOSFET). The MOSFET then was connected to the interfacing circuit. The sensitivity of the TiO₂ thin film towards pH buffer solution was measured by dipping the sensing membrane in pH4, pH7 and pH10 buffer solution. For comparison, a sample of bare-ITO was also tested to see its sensitivity. We found that the TiO₂ thin film annealed at 400 °C for 15 min gave the highest sensitivity compared to other annealing conditions and also compared to the bare ITO substrate with the value of 44.30 mV/pH. This showed that TiO₂ thin film can be used for pH sensing and the post-deposition treatment of the thin film can influence the sensing ability. We also measured the TiO₂ thin films’ current – voltage (I-V) characteristics. Relating the I-V characteristic of the thin films and sensitivity, the sensing membrane with higher conductivity gave better sensitivity.

• Periodical: Applied Mechanics and Materials (Volume 749)
• Pages: 197-201
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.749.197
• Online since: April 2015
• Authors: Rohanieza Abdul Rahman*, Muhammad Al Hadi Zulkefle, Wan Fazlida Hanim Abdullah, Sukreen Hana Herman
• Keywords: Extended-Gate Field Effect Transistor, Post-Deposition Treatment, Sol-Gel Method, Titanium Dioxide

References

[1] J. L. Chiang, J. C. Chen, Study of the pH-ISFET and EnFET for biosensor applications, J. Med. Biol. Eng., vol. 21, no. 3, pp.135-146, (2001).

[2] J. van Der Spiegel, I. Lauks, P. Chan, and D. Babic, The extended gate chemical sensitive field effect transistor as multi-species microprobe, Sens. Actuators A, Phys., vol. 4, pp.291-298, Jan (1983).

DOI: 10.1016/0250-6874(83)85035-5

[3] Sarah, M. S P; Musa, M.Z.; Asiah, M. N.; Rusop, M., Electrical conductivity characteristics of TiO2 thin film, Electronic Devices, Systems and Applications (ICEDSA), 2010 Intl Conf on , vol., no., p.361, 364, 11-14 Apr. (2010).

DOI: 10.1109/icedsa.2010.5503040

[4] J. Yu, X. Zhou, and Q. Zhou, Photocatalytic activity of nanometer TiO2 thin film prepared by the sol-gel method, Materials Chemistry and Physics, vol. 69, pp.25-29, (2001).

DOI: 10.1016/s0254-0584(00)00291-1

[5] Y. C. Lee, and Y. J. Jung, Enhanced efficiency of dye-sensitized TiO2 solar cells (DSSC) by doping of metal properties, Solar Energy, vol. 83, pp.1499-1508, (2009).

[6] Kamarozaman, N.S.; Aznilinda, Z.; Herman, S.H.; Bakar, R.A.; Rusop, M., Effect of annealing duration on the memristive behavior of Pt/TiO2/ITO memristive device, Semiconductor Electronics (ICSE), 2012 10th IEEE International Conference on, vol., no., p.703, 706, 19-21 Sept. (2012).

DOI: 10.1109/smelec.2012.6417240

[7] Rosdan, M.A.; Herman, S.H.; Abdullah, W.F.H.; Kamarozaman, N.S.; Syono, M.I., Sputtered titanium dioxide thin film for Extended-Gate FET sensor application, Micro and Nanoelectronics (RSM), 2013 IEEE Regional Symposium on , vol., no., p.219, 222, 25-27 Sept. (2013).

DOI: 10.1109/rsm.2013.6706513

[8] Pin-Chuan Yao, Jung-Lung Chiang, Ming-Chih Lee, Application of sol–gel TiO2 film for an extended-gate H+ ion-sensitive field-effect transistor, Solid State Sciences, Volume 28, Feb. (2014).

DOI: 10.1016/j.solidstatesciences.2013.12.011