Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO₂ thin films

Abstract

In-situ pure TiO₂ and Fe-doped TiO₂ thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO₂ thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO₂ thin films by adding precursor K₄(FeCN)₆·3H₂O into the Na₃PO₄ electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K₄(FeCN)₆·3H₂O increasing, eventually affecting the ethanol sensing performances of TiO₂ thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe³⁺ substituting for Ti⁴⁺.

Keywords

thin films / titanium dioxide / doping / iron / micro-arc oxidation / ethanol sensors

References

[1] Korotcenkov G. Metal oxides for solid-state gas sensors: what determines our choice?. Mater. Sci. Eng. B, 2007, 139(1): 1

[2] L.L. Xing, C.H. Ma, Z.H. Chen, Y.J. Chen, and X.Y. Xue, High gas sensing performance of one-step-synthesized Pd-ZnO nanoflowers due to surface reactions and modifications, Nanotechnology, 22(2011), No.21, art. No.215501.

[3] Wisitsoraat A., Tuantranont A., Comini E., Sberveglieri G., Wlodarski W. Characterization of n-type and p-type semiconductor gas sensors based on NiO_x doped TiO₂ thin films. Thin Solid Films, 2009, 517(8): 2775

[4] Zhang R.B., Li F.S. Electrical properties of titania films by hydrolysis of alkoxide titanium in micelles. J. Mater. Sci., 2005, 40(18): 4929

[5] Al-Homoudi I.A., Thakur J.S., Naik R., Auner G.W., Newaz G. Anatase TiO₂ films based CO gas sensor: film thickness, substrate and temperature effects. Appl. Surf. Sci., 2007, 253(21): 8607

[6] Sadek A.Z., Partridge J.G., McCulloch D.G., Li Y.X., Yu X.F., Wlodarski W., Kalantar-zadeh K. Nanoporous TiO₂ thin film based conductometric H2 sensor. Thin Solid Films, 2009, 518(4): 1294

[7] Chaudhari G.N., Bambole D.R., Bodade A.B., Padole P.R. Characterization of nanosized TiO₂ based H2S gas sensor. J. Mater. Sci., 2006, 41(15): 4860

[8] Bârsan N., Weimar U. Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO₂ sensors in the presence of humidity. J. Phys. Condens. Matter, 2003, 15(20): 813

[9] Jun Y.K., Kim H.S., Lee J.H., Hong S.H. CO sensing performance in micro-arc oxidized TiO₂ films for air quality control. Sens. Actuators B, 2006, 120(1): 69

[10] Korotcenkov G. The role of morphology and crystallographic structure of metal oxides in response of conductometrictype gas sensors. Mater. Sci. Eng. R, 2008, 61, 1

[11] Zeng W., Liu T.M. Hydrogen sensing characteristics and mechanism of nanosize TiO₂ dope with metallic ions. Phys. B, 2010, 405(2): 564

[12] Teleki A., Bjelobrk N., Pratsinis S.E. Flame-made Nb- and Cu-doped TiO₂ sensors for CO and ethanol. Sens. Actuators B, 2008, 130(1): 449

[13] Garzella C., Comini E., Bontempi E., Depero L.E., Frigeri C., Sberveglieri G. Sol-gel TiO₂ and W/TiO₂ nanostructured thin films for control of drunken driving. Sens. Actuators B, 2002, 83(1–3): 230

[14] Alessandri I., Comini E., Bontempi E., Faglia G., Depero L.E., Sberveglieri G. Cr-inserted TiO₂ thin films for chemical gas sensors. Sens. Actuators B, 2007, 128(1): 312

[15] Sharma R.K., Bhatnagar M.C., Sharma G.L. Effect of Nb metal ion in TiO₂ oxygen gas sensor. Appl. Surf. Sci., 1996, 92, 647

[16] Zakrzewska K., Radecka M., Rekas M. Effect of Nb, Cr, Sn additions on gas sensing properties of TiO₂ thin films. Thin Solid Films, 1997, 310(1–2): 161

[17] Castañeda L., Maldonado A., Olvera M. d. l. L. Sensing properties of chemically sprayed TiO₂ thin films using Ni, Ir, and Rh as catalysts. Sens. Actuators B, 2008, 133(2): 687

[18] Zhang W.H., Zhang W.D., Zhou J.F. Solvent thermal synthesis and gas-sensing properties of Fe-doped ZnO. J. Mater. Sci., 2010, 45(1): 209

[19] Wan L., Li J.F., Feng J.Y., Sun W., Mao Z.Q. Photocatalysts of Cr doped TiO₂ film prepared by micro arc oxidation. Chin. J. Chem. Phys., 2008, 21(5): 487

[20] Li J.F., Wan L., Feng J.Y. Study on the preparation of titania films for photocatalytic application by micro-arc oxidation. Sol. Energy Mater. Sol. Cells, 2006, 90(15): 2449

[21] Wei D.Q., Zhou Y., Yang C.H. Characteristic and microstructure of the microarc oxidized TiO₂-based film containing P before and after chemical- and heat treatment. Appl. Surf. Sci., 2009, 255(18): 7851

[22] Franke M.E., Koplin T.J., Simon U. Metal and metal oxide nanoparticles in chemiresistors: Does the nanoscale matter?. Small, 2006, 2(1): 36

[23] Wang Z.X., Liu L. Synthesis and ethanol sensing properties of Fe-doped SnO₂ nanofibers. Mater. Lett., 2009, 63(11): 917