Single step synthesis of rutile TiO2 nanoflower array film by chemical bath deposition method T. Dhandayuthapani, R. Sivakumar, and R. Ilangovan Citation: AIP Conference Proceedings 1728, 020286 (2016); doi: 10.1063/1.4946337 View online: http://dx.doi.org/10.1063/1.4946337 View Table of Contents: http://scitation.aip.org/content/aip/proceeding/aipcp/1728?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Synthesis of anatase and rutile TiO2 nanostructures from natural ilmenite AIP Conf. Proc. 1710, 030023 (2016); 10.1063/1.4941489 TiO2 thin film deposition by chemical methods AIP Conf. Proc. 1425, 159 (2012); 10.1063/1.3681991 Synthesis and Characterization of SnO2 Thin Films by Chemical Bath Deposition AIP Conf. Proc. 1415, 231 (2011); 10.1063/1.3667263 Room temperature ferromagnetism in N-doped rutile TiO2 films J. Appl. Phys. 109, 07C302 (2011); 10.1063/1.3535427 The deposition behavior of SiO 2 –TiO 2 thin film by metalorganic chemical vapor deposition method J. Vac. Sci. Technol. A 18, 2384 (2000); 10.1116/1.1287154
Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions IP: 158.222.0.225 On: Tue, 10 May 2016 15:26:34
Single Step Synthesis of Rutile TiO2 Nanoflower Array Film by Chemical Bath Deposition Method T. Dhandayuthapani1, R. Sivakumar2, and R. Ilangovan3,a) 1
Department of Nanoscience and Technology, Alagappa University, Karaikudi – 630 004, India 2 Directorate of Distance Education, Alagappa University, Karaikudi – 630 004, India 3 National Centre for Nanosciences and Nanotechnology, University of Madras, Chennai – 600 025, India a)
Corresponding author:
[email protected]
Abstract. Titanium oxide (TiO2) nanostructures such as nanorod arrays, nanotube arrays and nanoflower arrays have been extensively investigated by the researchers. Among them nanoflower arrays has shown superior performance than other nanostructures in Dye sensitized solar cell, photocatalysis and energy storage applications. Herein, a single step synthesis for rutile TiO2 nanoflower array films suitable for device applications has been reported. Rutile TiO2 nanoflower thin film was synthesized by chemical bath deposition method using NaCl as an additive. Bath temperature induced evolution of nanoflower thin film arrays was observed from the morphological study. X-ray diffraction study confirmed the presence of rutile phase polycrystalline TiO2. Micro-Raman study revealed the presence of surface phonon mode at 105 cm-1 due to the phonon confinement effect (finite size effect), in addition with the rutile Raman active modes of B1g (143 cm-1), Eg (442 cm-1) and A1g (607 cm-1). Further, the FTIR spectrum confirmed the presence of Ti-O-Ti bonding vibration. The Tauc plot showed the direct energy band gap nature of the film with the value of 2.9 eV.
INTRODUCTION Rutile TiO2 nanostructured thin film has attracted considerable attention in the area of Dye-sensitized solar cell [1], supercapacitor [2], photocatalysis [3] and photo-electrochemical cell [4]. Wide variety of rutile TiO2 nanostructures such as nanobelts [5], nanorods [2] and nano-trees [5] are extensively investigated by the researchers. Among these nanostructures, nanoflower array [1] has shown excellent performance in applications such as Dyesensitized solar cells [1], antireflection coating [6], and photocatalysis [3]. Nanoflower array reported to have shown superior performance than nanorod array in solar cell application [1]. Though various solution based techniques are available to prepare nanostructured TiO2 thin films, chemical bath deposition (CBD) is a simple technique which can be utilized for the preparation of nanostructured TiO2 thin films. Herein we report a facile single step synthesis for the preparation of rutile TiO2 nanoflower array film by CBD using NaCl as an additive. The structural, vibrational, morphology and optical properties of rutile TiO2 nanoflower array film are discussed in detail.
EXPERIMENT In ambient condition 10 ml of HCl was added dropwise into 80 ml of deionized water to maintain a pH of 0.85 and then 10 ml of 1.5 M NaCl was added to that solution. The solution was stirred for 30 minutes and further 1 ml of titanium tetraisopropoxide was added to that final solution. The final solution mixture was stirred for 30 minutes and the cleaned glass substrates were immersed vertically in the growth solution. Now, the beaker containing the substrate and growth solution was sealed and kept in the CBD bath. The temperature of the growth solution was maintained at 140oC and the deposition was carried out for 3 hours. The nanoflower array film was obtained after washing the obtained products with distilled water. In order to understand the morphological evolution of deposited films, the experiments were also carried out at different bath temperatures like 100oC and 120oC.
International Conference on Condensed Matter and Applied Physics (ICC 2015) AIP Conf. Proc. 1728, 020286-1–020286-4; doi: 10.1063/1.4946337 Published by AIP Publishing. 978-0-7354-1375-7/$30.00
020286-1 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions IP: 158.222.0.225 On: Tue, 10 May 2016 15:26:34
RESULTS AND DISCUSSION Structural Study
FIGURE 1. X-ray diffraction pattern of deposited rutile TiO2 thin film at 140oC.
Fig. 1 shows the x-ray diffraction pattern (XRD) of deposited thin film at 140oC. The diffraction peaks match exactly with rutile phase TiO2 (JCPDS file No. 21-1276). The crystallite size of film is about 12 nm as calculated from the full width at half maximum of (110) peak using Scherrer equation. The calculated lattice constant values are a = 0.462 nm and c = 0.285 nm and the volume of the cell V= 61.183 (ǖ)3, which are in good agreement with the JCPDS data.
Surface Morphological Study 100oC
120oC
5ȝm
5ȝm
140oC
5ȝm
FIGURE 2. FESEM images of TiO2 films deposited at various bath temperatures.
Fig. 2 shows the field emission scanning electron microscopic (FESEM) images of TiO2 thin films deposited at 100oC, 120oC and 140oC. Based on the temperature induced morphology results at 100oC, TiO2 formed as large number of nuclei which are aggregated into a ball like structure. At 120oC, the surface of ball like nanoparticles dissolved to form a nanoflower like structures. At the temperature of 140oC, nanoflowers are further recrystallized to form a sheet like structures in order to attain more stable thermodynamic state .This process is called dissolution and recrystallization. Addition of NaCl into growth solution plays crucial role for the formation of TiO2 nanoflower arrays [7]. In the absence of NaCl, no flower like structures was obtained [7]. In the present work, the pH (0.85) of the growth solution and the bath temperature (140oC) plays an important role to get the nanoflower array film. The compositional purity of the deposited film was confirmed by EDAX measurement as we observed only the signals corresponding to Ti and O in the spectrum (spectrum not shown here). The elemental composition of deposited TiO2 film at 140oC was found to be 76.93 wt.% of oxygen and 26.03 wt.% of titanium.
020286-2 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions IP: 158.222.0.225 On: Tue, 10 May 2016 15:26:34
Vibrational Property
FIGURE 3. (a) Raman spectrum and (b) FTIR spectrum of deposited TiO2 film at 140oC.
Fig. 3(a) shows the micro-Raman spectrum of deposited TiO2 thin film at 140oC. The first order Raman spectrum of rutile single crystal shows four Raman active fundamental modes [8]: B1g (143 cm-1), Eg (447 cm-1), A1g (612 cm-1), and B2g (826 cm-1). In our case we observed Eg at 442 cm-1, A1g at 607 cm-1 and B1g at 143 cm-1. In addition, we have observed a surface phonon mode at 105 cm-1 which is due to the phonon confinement effect because of the finite particle size. Further, thepeak observed at 243 cm-1 is due to the multi phonon scattering effect. Furthermore, the observed Raman bands confirm that the deposited TiO2 thin film is corresponds to rutile phase. This is in line with the x-ray diffraction data. Fig. 3(b) shows the FT-IR spectrum of TiO2 thin film deposited at 140oC. The observed peaks at 465 cm-1, 542 cm-1, 634 cm-1 and 742 cm-1 are related to the Ti-O-Ti bonding vibrations [9]. No peak related to Ti-OH vibration was observed in the study which confirmed the purity of deposited films.
Optical Properties
FIGURE 4. (a) Absorbance spectrum and (b) Tauc plot of TiO2 film deposited at 140oC.
Fig. 4(a) shows the absorbance spectrum of TiO2 thin film deposited at 140oC. The onset of absorbance was observed at 380 nm and the absorbance edge was observed at 415 nm which is related to the energy band gap of rutile TiO2. The maximum transmittance of 36% was observed, the low transmittance value might due to the nanostructured morphological nature of the films (transmittance spectrum not shown here). Fig. 4(b) shows the Tauc plot of ((ĮhȞ)2 versus photon energy) TiO2 thin film deposited at 140oC, the bandgap value was found to be 2.9 eV which exactly matches with the band gap value of rutile TiO2 [9] .
CONCLUSIONS Rutile TiO2 nanoflower array thin films have been successfully synthesized using single step chemical bath deposition technique. Bath temperature induced evolution of nanoflower array was observed from the morphological
020286-3 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions IP: 158.222.0.225 On: Tue, 10 May 2016 15:26:34
study. X-ray diffraction study confirmed the presence of rutile phase polycrystalline TiO2. Micro-Raman study revealed the presence of surface phonon mode at 105 cm-1 due to the phonon confinement effect (finite size effect), in addition with the rutile Raman active modes of B1g (143 cm-1), Eg (442 cm-1) and A1g (607 cm-1). Further, the FTIR spectrum confirmed the presence of Ti-O-Ti bonding vibration. The Tauc plot showed the direct energy band gap nature of the film with the value of 2.9 eV.
REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.
M. Ye, H.Y.Liu, C.Lin and Z.Lin, Small, 9, 312 (2013). A.Ramadoss and S.J.Kim J. Alloy. Compd., 516, 262 (2013). G.Tian, Y.Chen, W.Zhou, K.Pan, C.Tian, X.Hang and H.Fu, CrystEngComm, 13, 2994 (2011). X.Sun, Q.Sun, Q.Zhang, Q.Zhu, H.Dong and L.Dong, J. Phys. D. Appl. Phys., 46, 095102 (2013). W.Zhou, X.Liu, J.Cui, D.Liu, J.Li, H.Jiang and H.Liu, CrystEngComm, 13, 4557 (2011). Q.Mu, Y.Li, H.Wang and Q.Zhang, J. Colloid. Interface. Sci., 365, 308 (2012). K.S.Park, K.M.Min, Y.H.Jin, S.D.Seo, G.H.Lee, H.W.Shim and D.W.Kim, J. Mater. Chem., 22, 15981 (2012). V. Swamy and B. C. Muddle, Appl. Phys. Lett., 89, 163118 (2006). M. M. Shirolkar, D. Phase, V. Sathe, J. R. Carvajal, R. J. Choudhary and S. K. Kulkarni J. Appl. Phys., 109, 123512 (2011).
020286-4 Reuse of AIP Publishing content is subject to the terms at: https://publishing.aip.org/authors/rights-and-permissions IP: 158.222.0.225 On: Tue, 10 May 2016 15:26:34
