Transparent semiconducting thin films of titanium dioxide (TiO

2
-
) were deposited on glass substrates by spincoating



technique and with thickness was in order of 150 ± 5 nm . The XRD analysis reveals that the films are
polycrystalline with an anatase crystal structure and a preferred grain orientation in the (101) direction. The optical
properties of the films were characterized by UV–visible spectrophotometry, which shows that the films are highly
transparent in the visible and near infrared , with an average value above (99 %), with energy gape (3.79 e.v ). The
dependence of the refractive index (n), extinction coefficient (k), and absorption coefficient (α) of the films on the
wavelength was investigated

Ahmed  J. hassan

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 111  J.Thi-Qar Sci.                         Vol.5 (3)                                   Dec./2015   ISSN 1991- 8690                                                                                                           1991 - 8690الدولي الترقيم      Preparation and Characterization of Titanium Dioxide (TiO2) Thin Films Prepared By Spin Coating Method  Ahmed J. Hassan  Department Of Physics- College Of Science- University Of Thi-Qar/ Iraq E-mail: ahmed.jhassan@yahoo.com  Abstract:          Transparent semiconducting thin films of titanium dioxide (TiO2) were deposited on glass substrates by spin-coating technique and with thickness was in order of 150  ± 5 nm . The XRD analysis reveals that the films are polycrystalline with an anatase crystal structure and a preferred grain orientation in the (101) direction. The optical properties of the films were characterized by UV–visible spectrophotometry, which shows that the films are highly transparent in the visible and near infrared , with an average value above  (99 %),  with energy gape (3.79 e.v ). The dependence of the refractive index (n), extinction coefficient (k), and absorption coefficient (α) of the films on   the wavelength was investigated.  keywords : titanium dioxide, Spin Coating Method.   (Spin Coater)  ( المحضرة بطريقة تدوير الطالءTiO2تحضير وتشخيص اغشية ثنائي اوكسيد التيتانيوم)  احمد جابر حسن جامعة ذي قار –كمية العموم  –قسم الفيزياء  الخالصة : عند درجة حرارة الغرفة  (  Spin Coater( باستعمال تقنية تدوير الطالء )TiO2تم في هذا البحث تحضير اغشية رقيقة لثنائي أوكسيد التيتانيوم )           X-rayسينية ). شخصت االغشية الرقيقة  المحضرة باستخدام حيود االشعة ال nm) 5±051)وتم ترسيب المحمول عمى قواعد زجاجية شفافة  وبسمك Diffraction  ), وتبين انها من نوعanatase  (وكذلك تمت قياس الخواص البصرية لالغشية باستخدام جهاز ,UV–visible spectrophotometry, )وكذلك تم قياس ( e.v 3.75اما فجوة الطاقة الممنوعة كانت ) (e.v 3.79(  وفجوة الطاقة المسموحة وكانت )%99سجمت اعمى قيمة لمنفاذية  عند ) االمتصاصية واالنعكاسية ومعامل االنكسار والخمود . 1. Introduction:         Titanium doxide (TiO2) thin films have attracted much attention due to their optical, physical, chemical, and electronic properties, including excellent transmittance of visible light, photocatalytic activity, high dielectric constant, high refractive index, and high chemical stability [ T.L. Chen, et al (2007) - P.D. Prajna, et al (2008)]. A variety of TiO2 films have been developed for several applications, such as solar cells [O. Regan and  Grätzel, (1991)],  photocatalysis [ K. Masaaki et al (2007) -  Š. Kment, et al (2012)], gas sensors [ Ibrahim A, et al (2007) ], and antireflective coatings [G. San Vicente, et al (2002) ]. It is well known that TiO2 is a n-type semiconductor with a wide indirect energy band gap [M. Gräzel, (1989) - N. Serpone, et al (2995) ]. TiO2 generally crystallizes in three structures, the tetrahedral anatase structure. The anatase and rutile structures belong to different space  121  J.Thi-Qar Sci.                         Vol.5 (3)                                   Dec./2015  groups but both have a tetragonal crystal lattice. Rutile is the most stable form of TiO2, whereas anatase and brookite are met stable and transform to the rutile phase upon heating [C.  Rath,  et al (2009) – H. Zhang, et al (1999) ]. The characteristics of TiO2 films depend on their crystal structure, orientation, and morphology, and  phase structure of the films during growth is important.  Various techniques have been used for the deposition of TiO2 films, such as sol–gel spin coating  [K. Pomoni,  et al (2008) - M. Morozova, et al (2011) ], spray pyrolysis [C. Natarajan, et al (1998) ], pulsed laser deposition [T.  Masahiro, et al (2000) ], e-beam evaporation [S.  Lianchao and  H. Ping, (2004)], chemical vapor deposition [S. Hongfu, et al (2008) ], and reactive magnetron sputtering [S. Boukrouh, et al (2008) ].   2. Experimental          The TiO2  sol was prepared using  of titanium chloride dissolved in hydrochloric acid As a solution ready for use (with purity 99.8% ). In the sol, the titanium concentration was 1 mol/L. glass substrates were successively cleaned with acetone, ethanol, and deionized water. TiO2 thin films were deposited on the glass substrates by spin coating (as illustrated in figure  (1) at room temperature with a rate of 3000 rpm for 30 s, then spin-coating step, the films were heated on a hot plate at 100 °C in air for 15 min to remove organic contaminations.  The X-ray diffractometer (ShimadZu 6000) Target: Cu kα, Voltage 40 KV, Current 30 MA. Where λ is the X-ray wavelength (1.54060 Å).. The absorptance and transmittance of the prepared films were measured using  UV- Visible recording Spectrophotometer( UV, VTC 100 )  in the wavelength range (300-1000 nm), as illustrated in figure (2).                              3. Results And Discussion 1. X- ray  Diffraction  Investigation  The X-ray diffraction of TiO2 films deposited on glass substrate was at room temperature. Figure (3) displays XRD spectrum of TiO2 film. It is obvious that the film is (polycrystalline and multiphase). The structure of TiO2 in XRD investigation is anatase titanium dioxide, which agrees with (ASTM) card, and with the previous study [I. Oja, et al (2006) ].      2. Transmittance (T)           Fig. (4) . Show the optical transmission as a function of wavelength in the range (300 – 1000 nm) for TiO2 films. The maximum transmittance observed was almost (99%). The figure show that the transmittance of film has a high value  at (λ>500nm), Fig. 1:  shows the device spin coating ( VTC 100 )   Fig.2:  shows the device UV- Visible recording Spectrophotometer  Fig. 3: The X-ray diffractograms of TiO2 films  121  J.Thi-Qar Sci.                         Vol.5 (3)                                   Dec./2015  i.e. in visible and near infrared regions. Our result is in good agreement with [ A. A.  Daniyan,  et al (2013)]       3. Absorbance (A)        Fig.5. shows the variety of observance as a function of wavelength, within the range (300 – 1000nm) for  TiO2 film's investigation.  In general the absorbance of films has low values in the visible and  near infrared region, this behavior can be explained as follows, at high wavelength the incident photons don’t have enough energy to interact with atoms, the photon will transmitted. When the wavelength decreases, the interaction between incident photon and material will occur.        4. Absorption Coefficient Measurements: (α)          Fig. ( 6 ) shows the relation of absorption coefficient as a function of incident photon energy for TiO2  thin films.  Also we can evidently see that TiO2  thin films have high  value of absorption coefficient (α > 105 cm-1 ) which leads to increasing the probability of occurrence direct transitions.       5. Optical Energy Gap (Eg)          Fig. ( 7 ) shows the relation of ( αhv )2  against photon energy, from straight line obtained at high photon energy the direct allowed energy gap could be determined which was equal (3.79  eV) and Fig. ( 8 ) shows direct forbidden energy gap equal (3.75 eV). Our result is in good agreement with [I.Karabay, et al (2012)].       Fig. 4:  the relation between transmittance and wavelength of TiO2 thin films Fig.5: relation between wavelength and absorptance of TiO2 thin films Fig. 6: absorption coefficient as function of energy photon of TiO2 thin films Fig. 7: relation between  (αhv)2   and  photon energy of TiO2 thin films ( e.g for Direct allowed transition )   122  J.Thi-Qar Sci.                         Vol.5 (3)                                   Dec./2015       6. Extinction Coefficient Measurements ( Ko) : Figure (9) illustrates variation of (Ko) as a function of wavelength for (TiO2) films. From the figure extinction coefficient decreasing with wavelength increasing, because of dependent on coefficient absorption.        7. Reflectance  (R):   We observed that reflectance have high value which decreasing with increasing of  wavelength for films, as in figure(10). The behavior of reflectance is in agreement with the behavior of transmittance and absorbance according to equation :  A+T+R = 1      8. Refractive Index ( n ) : Figure (11) shows relation between refractive index and wavelength, we can notice that the behavior of refractive index with wavelength is the same behavior reflection, which means that the reflective index increase with increase photon energy       References:  Ayodele Abeeb Daniyan , Lasisi Ejibunu Umoru , Bankole Olunlade  , (2013 ) “Preparation of Nano-TiO2 Thin Film Using  Spin Coating Method“ journal of minerals and materials charactrazition and engineering  , 1 , 138 -144  C. Natarajan, N. Fukunaga, G. Nogami, (1998) Thin Solid Films. 322:6.   Chandana Rath, P Mohanty, A C Pandey, N C Mishra, (2009) J. Phys. D: Appl. Phys. 42:205101.   G. San Vicente, A. Morales, M.T. Gutiérrez, (2002) Thin Solid Films. 403–404:335.    H. Zhang, J.F. Banfield, (1999) Am. Mineral Am Mineral 1999, 84:528-535. Fig. 8:  relation between  (αhv)2/3  and  photon energy of TiO2 thin films ( e.g for Direct forbidden transition )  Fig. 9: extinction coefficient as function of wavelength of TiO2 thin films Fig. 10: relation between wavelength and reflectance  of TiO2 thin films Fig. 11: refraction index  as function of wavelength of TiO2 thin films  123  J.Thi-Qar Sci.                         Vol.5 (3)                                   Dec./2015  I.Karabay,S.Aydın Yüksel, F. Ongül, S. Öztürk and M. 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Preparation and Characterization of Titanium Dioxide (TiO ) Thin Films Prepared By Spin Coating Method    2

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Preparation and Characterization of Titanium Dioxide (TiO ) Thin Films Prepared By Spin Coating Method 2

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