study of annealing effect on the some physical properties of nanostructured tio2 films prepared by...

3102.................. العدد الثالث جملة كلية الرتبية ...........................................

139

Study of Annealing Effect on the Some Physical Properties of

Nanostructured TiO2 films prepared by PLD

Ali A.Yousif ●

, Sarmad S. Al-Obaidi ●●

Department of Physics, College of Education, University of Al-Mustansiriyah, Baghdad,

Iraq ●

Email: [email protected], ●●

Email: [email protected]

ذات TiO2 لألغشية الفيزيائية الخصائص بعض على التلدين تأثير دراسة

PLD بتقنية المصنعة النانوي التركيب

العبيدي صبيح سرمد ,يوسف أحمد علي .د.م.أ

ية, بغذاد, العراقتربية, الجامعة المستنصرقسم الفيزياء, كلية ال

82/11/8118تقذيم البحث:

82/18/8118قبول نشر البحث:

Abstract

Nanostructured Titanium Dioxide (TiO2) thin films were prepared by pulsed

laser deposition (PLD) on the glass substrates. The effects of different annealing

temperature (400, 500 and 600 °C) towards the some physical properties such as

structural, morphological and optical have been studied. From X-ray diffraction

result, the crystallinity of TiO2 thin films improved at higher annealing

temperature. It also could be observed that the rutile phase start to exist at

annealing temperatures of 500 °C and 600 °C. The Full Width at Half

Maximum (FWHM) of the (101) peaks of these films decreases from 0.450° to

0.301° with increasing of annealing temperature. AFM measurements confirmed

that the films grown by this technique have good crystalline and homogeneous

surface. The Root Mean Square (RMS) value of thin films surface roughness

increased with increasing of the annealing temperature. From UV-VIS

spectrophotometer measurements, the optical transmission results shows that the

mailto:[email protected]

3102جملة كلية الرتبية ............................................................. العدد الثالث

140

transmission over than ~65% in the near-infrared region which decrease with the

increasing of annealing temperatures. The allowed indirect optical band gap of

the films was estimated to be in the range from 3.49 to 3.1 eV. The allowed

direct band gap was found to decrease from 3.74 eV to 3.55 eV with the increase

of annealing temperature. The refractive index of the films was found from 2.27

-2.98 at 550nm. The extinction coefficient, real and imaginary parts of the

dielectric constant increase with annealing temperature.

KEYWORDS - Titanium Dioxide, Pulsed Laser Deposition, Structural,

Morphology, Optical Properties, TiO2 Films.

خالصةال

حشسيب انهيضس بىاسطت حقيت انبىيت TiO2)أغشيت اوكسيذ انخيخبيىو ) حسظيشحى

044, 044, 044) بذسخبث انسشاسة انخخهفت حأثيش انخهذي قىاعذ صخبخيت. عه (PLD) انبضي

سج.سوانبصشيت قذ د طبىغشافيت,انعه بعط انخصبئص انفيضيبئيت يثم انخشكبيت دسخت يئىيت(

حبي ي خأج زيىد االشعت انسييت بأ حبهىس األغشيت انشقيقت نثبثي اوكسيذ انخيخبيىو حسس في

وكزنك يك ا ي الزظ بأ طىس انشوحيم يبذأ ببنظهىس في دسخبث اعه دسخت زشاسة حهذي

ثبئي انسي عذ يخصف انقت ألغشيت عشض ا .دسخت يئىيت 044و 044زشاسة انخهذي

بضيبدة دسخت زشاسة انخهذي. 0.301°ان 0.450°قذ صغش ي (101)اوكسيذ انخيخبيىو ألبط

نهب حبهىس غشيت انبث بهز انطشيقتبأ األ (AFM)يدهش انقىي انزسيت قيبسبث ثاكذو

انسطر نألغشيت انشقيقت وخشىت (RMS) يشبع اندزس انخىسظ ا قيىووراث سطر يخدبس. خيذ

قيسج يطيبف انفبريت نألشعت انشئيت وفىق انبفسديت ) ي انخهذي. دسخت انسشاسة صيبدة يعحضداد

في ٪65 ~ بأ هبنك فبريت أكثش ي ظهشح انفبريت انضىئيت خبئح UV-VIS)بىاسطت يطيبف

قت فدىة انطب .انخهذي دسخبث انسشاسة صيبدة يع حقم وانخييطقت االشعت حسج انسشاء انقشيبت

ووخذ انكخشو فىنج. 9.3ان 9.03انبصشيت انسىزت انغيش يببششة األغشيت قذسة بسذود ي

بضيبدة ,إنكخشو فىنج 9.00ان 0..9ا فدىة انطبقت انبصشيت انسىزت انببششة حقم ي

عذ انطىل 2.32ان .2.2دسخت زشاسة انخهذي. ووخذ ا يعبيم االكسبس نألغشيت حخشاوذ ي

بضيبدة دسخت وثببج انعضل انسقيقي وانخيبني قذ صدادا بىيخش. ا يعبيم انخىد 004انىخي

زشاسة انخهذي.


141

1. INTRODUCTION

The experimental and theoretical study of semiconductor

nanocrystallites has generated tremendous technological and scientific

interest recently due to the unique electronic and optical properties and

exhibition of new quantum phenomena. In the semiconductor technology,

laser induced crystallization is used because it presents selective optical

absorption and low processing temperature [1]. Oxides reveal an excellent

chemical and mechanical property and do not show deterioration. As one of

the important wide band gap (Eg3 eV) oxides, TiO2 has been subject to

extensive academic and technological research for decades, due to its

unique properties such as[2,3]: (1) High electro-chemical properties. (2)

Non-toxic, inexpensive, highly photoactive, and easily synthesized and

handled. (3) Highly photostable. (4) With high dielectric constant,

hardness, and transparency TiO2 films are applicable for storage capacitor

in protective coatings, and optical components. Nanocrystalline titanium

dioxide thin films have important applications in the field of optoelectronic

materials. TiO2 is an important photocatalytic material [4], which can be

used in the form of thin films in dye-sensitized solar cells [5] and anti-

reflection coatings [6]. Titanium dioxide occurs in three crystalline

polymorphs: rutile (tetragonal), anatase (tetragonal), and brookite

(orthorhombic) [1]. Many deposition methods have been used to prepare

TiO2 thin films, such as electron-beam evaporation [7], ion-beam assisted

deposition [8], DC reactive magnetron sputtering [9], RF reactive

magnetron sputtering [10], sol-gel dip coating method [11], sol-gel spin

coating method [12], chemical vapor deposition [13], plasma enhanced

chemical vapor deposition [14] and pulsed laser deposition (PLD) [15].

Wide variations in the optical and physical properties of TiO2 thin films

deposited by different techniques have been reported. For pulsed laser

deposition derived films, film properties such as crystallinity, particle size,

degree of homogeneity, etc. depend largely on annealing temperature and

substrate topography [16]. Pulsed laser deposition proved to be a

favorable technique for the deposition of titanium dioxide at different

technological conditions on different substrates. That supposed to result in

the different structural and micro structural properties, different surface

morphology of the nanostructures to be obtained. A number of studies on

the deposition of TiO2 films by pulsed laser have appeared in the literature

recently [17, 18].


142

In this study, the influence of annealing in the 400 to 600 ᵒC range on

the structural (XRD), morphological (AFM) and optical (UV-VIS

spectrophotometer) properties of TiO2 thin films was investigated.

2. EXPERIMENTAL DETAILS

TiO2 thin films sintered titanium target of high - purity 99.99% was

mounted in a locally design vacuum chamber and ablated by a double

frequency with Q-switched Nd:YAG pulsed laser operated at 532 nm, pulse

duration of about 10 ns and 0.4 J/cm2 energy density were focused on the

target to generate plasma plume. Glass (Made in China) was used as

substrates thin films and grown in oxygen environment with O2 partial

pressure of 10-2

mbar at substrate temperature of 300 °C. The deposited

thin films were grown typically 10 minutes after cooling to room

temperature. Thin films were annealed at 400 °C, 500 °C and 600 °C in

University of Al-Mustansiriyah using an electric furnace for 2 h in air. The

crystallinity of the prepared films was analyzed using X-ray Diffraction

(XRD) measurements (Shimadzu 6000 made in Japan) in Ministry of

Science and Technology using Cu Kα radiation at 1.5406 Å and operating

at an accelerating voltage of 40 kV and an emission current of 30 mA. Data

were acquired over the range of 2θ from 20° to 60°. For morphological

investigations, Atomic Force Microscope (AFM) images were recorded

using nanoscope scanning probe microscope controller in a tapping mode.

The AFM images were used to observe the surface roughness and

topography of deposited thin films. Measurements were made AFM at the

Ministry of Science and Technology. The absorption spectra of TiO2 thin

films were studied by UV-visible (Shimadzu UV- 1650 PC made by

Phillips, Japanese company) spectrophotometer in spectral range of (300-

900) nm. The data from transmission spectrum could use in the calculation

of the absorption coefficient )α( by using the following equation:

…………………………..…………………1

Where d: is the thickness of thin film, and T is the transmission.

The absorption coefficient )α( and optical energy gap )Eg) are related by:

[19] αhυ = A)hυ-Eg)n …………….…………………………......... 2

Where A: is constant depending on transmission probability, h: is Plank's

constant, υ: is the frequency of the incident photon, Eg: is the energy gap of

TIn

d

11


143

the material and n has different values depending on the nature of

absorption process.

Thickness measurements by optical interferometer method, where

carried out using a He-Ne laser at λ=632.8 nm. The film thickness is about

200 nm for all TiO2 films at same deposition conditions; the number of

laser pulses is in the range of 100 pulses.

3. EXPERIMENTAL RESULTS

3.1 Structural Properties

The fig.1 shows X-ray diffraction patterns for TiO2 thin films prepared

by pulsed laser deposition on glass substrates at 300 °C at different

annealing temperatures (400, 500, and 600)°C with a fixed annealing time

of 2 h in air. As-deposited TiO2 film at 300 °C is found to be crystalline

and possesses anatase structure as it shows few peaks of anatase (101) and

(004), while film annealed at 400 °C having peaks of anatase (101), (004)

and (200), film annealed at 500 °C having peaks of anatase (101), (004),

(200) and rutile (110) and film annealed at 600 °C having peaks of anatase

(101), (004), (200) and rutile (110), (211). The diffraction peaks are in

good agreement with those given in JCPD data card (JCPDS No. 21– 1272

& 21 – 1276) for TiO2 anatase and rutile. The X-ray spectra show well-

defined diffraction peaks showing good crystallinity, it was found that all

the films were polycrystalline with a tetragonal crystal structure and no

amorphous phase is detected because high substrate temperatures can

achieve the sufficient energy to generate crystalline phases [20]. X-ray

diffraction analysis revealed that TiO2 thin films are amorphous if the

temperature substrate is lower than 300 °C [21]. The location of the (101)

peaks is shifted to lower 2θ angles from 2θ=25.27° to 2θ=25.11

°. It was


144

%100)(

c

ccStrain

found that anatase films were deposited and crystallized effectively for

heated substrate at 300 °C and working pressure of 10-2

Torr. The reason

may be that the kinetic energy of the particle is high enough to initiate

crystallization. For the samples annealed at 500 and 600 °C, other

characteristic peaks of anatase and rutile phase. These results are in

agreement with other reports on the mixed phase TiO2 by PLD method [22-

24].The transformation from anatase to rutile occurs at temperatures higher

than 500 °C under vacuum.

The lattice constants, in the diffraction pattern of TiO2 films are given

in table 1. The lattice constants obtained are found to be in good agreement

with JCPD.

The values of Full Width at Half Maximum (FWHM) of the peaks

decreases with annealing temperature, this goes in agreement with the

previous work [25]. The average grain size (g) in thin films is calculated

using Scherer’s formula: [26]

g = (0.94 λ( / [Δ)2 θ( cosθ] ……….........….………..…..………3

Where )λ( is the X-ray wavelength )Å(, Δ)2θ( FWHM )radian( and )θ( Bragg

diffraction angle of the XRD peak (degree).

The values of average grain size listed in table 2 shows an increasing

with increasing annealing temperature for TiO2 thin films. The micro strain

)δ( depends directly on the lattice constant (c) and its value related to the

shift from the JCPD standard value which could be calculated using the

relation: [27]

……………………..…………....4

Where (c) and (co) are the lattice parameters of the thin film from

experimental worked and TiO2 thin film obtained from JCPDS respectively.


145

c

cc

c

ccccSs

13

121133132

2

)(2

)()(

)()()(

0

1

0

hklIhklIN

hklIhklIhklT

r

C

The film annealed at 600 ºC temperature showed the maximum

compressive strain (3.640 ×10-3

), which decreased to nearly zero at 500 ºC,

as shown in table 2. The calculation of the film stress is based on the strain

model, which could be calculated using the relation: [27]

……………………………..……5

The values of the elastic constants from single crystalline TiO2 are used,

c11=208.8 GPa, c33=213.8 GPa, c12=119.7 GPa and c13=104.2 GPa [27].

The values of texture coefficient (Tc) of the thin films are listed in table

2. The texture coefficient is calculated using the relation: [28]

………………………………..6

Where (I) is the measured intensity, (Io) is the JCPDS standard intensity,

(Nr) is the reflection number and (hkl) is Miller indices.

For crystal plane (101), the values of texture coefficient decrease with

increasing of annealing temperature.

3.2 Morphological Properties

Fig. 2 shows the AFM images of the TiO2 thin films deposited at 300 °C

temperature and annealed at 400, 500 and 600 °C. The surface morphology

reveals the nano-crystalline TiO2 grains. The surface morphology of the

TiO2 thin films changed with the different annealing temperatures, as

observed from the AFM micrographs fig. 2 proves that the grains are semi

uniformly distributed within the scanning area )10 μm × 10 µm(, with

individual columnar grains extending upwards.

The values of the root mean square (RMS) and surface roughness of

TiO2 films shown in the table 3, the root mean square (RMS) and surface


146

roughness increased with increasing the annealing temperature, this result

is in agreement with the previous work [29]. The surface roughness of the

TiO2 thin films increases with film thickness, annealing temperature, and

annealing time [30].

3.3 Optical Properties

The optical transmittance measurements of the TiO2 films depend

strongly on the annealing temperature as shown in fig. 3. It is found that

average transmittance of as-deposited TiO2 films is about 65% in the near-

infrared region. The films annealed at 600 °C shows a significant decrease

in the range from 350nm to 900nm transmittance as shown in the fig. 3. It

is clearly, that the increasing of the annealing temperature has an obvious

effect on the transmittance decreasing, and this is resulted from roughness

increasing for film surface and increase of the surface scattering of the light

by increasing the columnar growth with needle and rod like shape [7, 29].

The absorption coefficient (α( is increasing with the annealing

temperature increasing as shown in the fig. 4, its value is larger than (104

cm-1

). This can be linked with increase in grain size and it may be

attributed to the light scattering effect for its high surface roughness [31].

Fig. 5 illustrates allowed direct electronic transition and fig. 6 illustrates

allowed indirect transition electronic. The energy band gap (Eg) values for

direct and indirect band gap for all the thin films are summarized in table 4.

It is found in literatures that TiO2 has a direct and indirect band gaps and

the band gap values changes according to the preparation parameters and

conditions [32]. From table 4 and the figures, it can be observed that (Eg) is

decreasing with the increasing of annealing temperature for all films. This

result is consistent with previous researches [25, 33]. Annealing led to


147

increased levels of localized near valence band and conduction band and

these levels ready to receive electrons and generate tails in the optical

energy gap and tails is working toward reducing the energy gap, or can be

attributed decrease energy gap to the increased size of particles in the films

[33].

Fig. 7 shows the variation in refractive index (n) of TiO2 films in the

wavelength range of (350-900) nm. The increase in the annealing

temperature results in an increase in the refractive index in the visible/near

infrared region. And the refractive index decreases as the wavelength

increases in the visible range. The values of the refractive index for the

films of different annealing temperatures vary in the range from 2.1 to 2.8

[20, 29, 34]. The increase may be attributed to higher packing density and

the annealing temperature influence on the morphology (change in

crystalline structure) of the films and hence caused change in the refractive

index.

The curves of extinction coefficient (Ko) for as-grown and annealed

TiO2 films are shown in fig. 8. Excitation coefficient behaves in the same

behavior of absorption, extinction coefficient increasing with increasing of

annealing temperature.

Figures 9 and 10 illustrate variation of real )εr) and imaginary )εi)

dielectric constant as a function of wavelength. The figures show that in all

samples the real part behaves like the refractive index because of the

smaller value of (Ko2) compared to (n

2(, while )εi) depends mainly on the

(Ko) values, which is related to the variation of the absorption coefficient.

This means that real part and the imaginary part increases when the

annealing temperature increasing.


148

4. CONCL1USION

The XRD results reveal that the deposited thin film and annealed at 400

°C of TiO2 have a good nanocrystalline tetragonal anatase phase structure.

Thin films annealed at 500 °C and 600 °C have mixed anatase and rutile

phase structure. And it is observed that the TiO2 films exhibit a

polycrystalline having (101), (110), (004), (200), (211) planes of high peak

intensities, also micro strain )δ( and grain size )g( increases while the

texture coefficient (Tc) decreases with increasing of annealing temperature.

The AFM results show the slow growth of crystallite sizes for the as-

grown films and annealed films from 400 to 600 °C. The root mean square

(RMS) is found to increase from 50.5 to 114 nm as the annealing

temperature is increased up to 600 °C.

The average transmittance (T) of deposited TiO2 films is about 65% in

the near-infrared region. The film annealed at 600 °C has the least

transmittance among the films, therefore; the film is good to be detector

within ultra-violet region range. The optical absorption coefficient )α( of

TiO2 films is about )α>104cm

-1), thus absorption coefficient has higher

increase at wavelength )λ<400 nm(. This converts to a large probability that

direct electronic transition will happen.

Also optical properties of TiO2 thin films show that the films have

allowed direct transition and allowed indirect transition. Increasing of the

annealing temperature for all films cause a decrease in the optical band gap

value and an increase in the optical constants (refractive index (n),

extinction coefficient (Ko), real )εr) and imaginary )εi) parts of the dielectric

constant).


149

REFERENCES

[1] O. Van Overschelde, G. Guisbiers, F. Hamadi, A. Hemberg, R. Snyders and

M. Wautelet, “Alternative to Classic Annealing Treatments for Fractally

Patterned TiO2 Thin Films,” Journal Applied Physics, Vol. 104, (2008), PP.

1-8.

[2] Y. Park and K. Kim, “Structural and Optical properties of Rutile and

Anatase TiO2 Thin Films: Effects of Co Doping,” Thin Solid Films, Vol.

484, (2005), PP. 34-38.

[3] A. Burns, G. Hayes, W. Li, J. Hirvonen, J. Demaree and S. Shah,

“Neodymium Ion Dopant Effects on the Phase Transformation in Sol-Gel

Derived Titania Nanostructures,” Materials science, Engineering, B111,

(2004), PP. 150-155.

[4] J. Wang, J. Yu, Z. Liu, Z. He, and R. Cai, “A Simple New Way to Prepare

Anatase TiO2 Hydrosol with High.Photocatalytic Activity,” Semiconductor

Science and Technology, Vol. 20, (2005), PP. 36-39.

[5] Y. Sung and H. Kim, “Sputter Deposition and Surface Treatment of TiO2

Films for Dye-Sensitized Solar Cells Using Reactive RF Plasma,” Thin

Solid Films, Vol. 515, (2006), P. 4996.

[6] M. Okada, M. Tazawa, P. Jin, Y. Yamada and K. Yoshimura, “Fabrication

of Photocatalytic Heat-Mirror with TiO2/TiN/ TiO2 Stacked Layers,”

Vacuum, Vol. 80, (2006), PP. 732-735.

[7] M. Habibi, N. Talebian and J. Choi, “The Effect of Annealing on

Photocatalytic Properties of Nanostructured Titanium Dioxide Thin

Films,” Dyes and Pigments, Vol. 73, (2007), PP. 103-110.

[8] C. Yang, H. Fan, Y. Xi, J. Chen and Z. Li, “Effects of Depositing

Temperatures on Structure and Optical Properties of TiO2 Film Deposited

by Ion Beam Assisted Electron Beam Evaporation,” Applied Surface

Science, Vol. 254, (2008), PP. 2685-2689.

[9] C. Tavares, J. Vieira, L. Rebouta, G. Hungerford, P. Coutinho, V. Teixeira, J.

Carneiro and A. Fernandes, “Reactive Sputtering Deposition of

Photocatalytic TiO2 Thin Films on Glass Substrates,” Mater. Sci. Eng.,

Vol. 138, (2007), PP. 139-143.


150

[10] A. Akl, H. Kamal and K. Abdel-Hady, “Fabrication and Characterization

of Sputtered Titanium Dioxide Films,” Applied Surface Science, Vol. 252,

(2006), P. 8651.

[11] M. Ghamsari and A. Bahramian, “High Transparent Sol–Gel Derived

Nanostructured TiO2 Thin Film,” Materials Letters, Vol. 62, (2008), PP.

361-364.

[12] Z. Wang, U. Helmersson and P. Käll, “Optical Properties of Anatase TiO2

Thin Films Prepared by Aqueous Sol–Gel Process at Low Temperature,”

Thin Solid Films, Vol. 405, (2002), PP. 50-54.

[13] H. Sun, C. Wang, S. Pang, X. Li, Y. Tao, H. Tang and M. Liu,

“Photocatalytic TiO2 Films Prepared by Chemical Vapor Deposition at

Atmosphere Pressure,” Journal of Non-Crystalline Solids, Vol. 354, (2008),

PP. 1440- 1443.

[14] W. Yang and C. Wolden, “Plasma-Enhanced Chemical Vapor Deposition

of TiO2 Thin Films for Dielectric Applications,” Thin Solid Films, Vol.

515, (2006), PP. 1708-1713.

[15] Y. Ming-Che, “Strategies to Improve the Electrochemical Performance of

Electrodes for Li-Ion Batteries,” PH.D Thesis, University of Florida,

(2012), PP.1-189.

[16] M. Mosaddeq-ur-Rahman, G. Yu, T. Soga, T. Jimbo and H. Ebisu M.

Umeno, “Refractive Index and Degree of Inhomogeneity of

Nanocrystalline TiO2 Thin Films: Effects of Substrate and Annealing

Temperature,” Journal Applied Physics, Vol. 88, No. 8, (2000), PP. 4634-

4641.

[17] M. Fusi, E. Maccallini, T. Caruso, C.S. Casari, A. Li Bassi, C.E. Bottani, P.

Rudolf, K. Prince and R. Agostino, “Surface Electronic and Structural

Properties of Nanostructured Titanium Oxide Grown by Pulsed Laser

Deposition,” Surface Science, Vol. 605, (2011), PP. 333-340.

[18] S. Sankar, K. Gopchandran, P. Kuppusami and S. Murugesan,

“Spontaneously Ordered TiO2 Nanostructures,” Ceramics International,

Vol. 37, (2011), PP. 3307-3315.


151

[19] C. Kittel, “Introduction to Solid State Physics,” 5th

ed., Willy, New York,

(1981).

[20] M. Hasan, A. Haseeb, H. Masjuki and R. Saidur, “Influence of Substrate

Temperatures on Structural, Morphological and Optical Properties of RF-

Sputtered Anatase TiO2 Films,” The Arabian Journal for Science and

Engineering, Vol. 35, (2010), PP. 147-156.

[21] K. Yahya, “Characterization of Pure and Dopant TiO2 Thin Films for Gas

Sensors Applications,” Ph.D Thesis, University of Technology Department

of Applied Science, (2010), PP. 1-147.

[22] N. Koshizaki, A. Narazaki and T. Sasaki, “Preparation of Nanocrystalline

Titania Films by Pulsed Laser Deposition at Room Temperature,” Applied

Surface Science, Vol. 197-198, (2002), PP. 624–627.

[23] T. Yoshida, Y. Fukami, M. Okoshi and N. Inoue, “Improvement of

Photocatalytic Efficiency of TiO2 Thin Films Prepared by Pulsed Laser

Deposition,” Japanese Journal of Applied Physics, Part 1, Vol. 44, No. 5,

(2005), PP. 3059-3062.

[24] S. Kitazawa, Y. Choi and S. Yamamoto, “In Situ Optical Spectroscopy of

PLD of Nano-Structured TiO2,” Vacuum, Vol. 74, No. 3-4, (2004), PP.

637-642.

[25] S. Pawar, M. Chougule, P. Godse, D. Jundale, S. Pawar, B. Raut and V.

Patil, “Effect of Annealing on Structure, Morphology, Electrical and

Optical Properties of Nanocrystalline TiO2 Thin Films,” Journal of Nano-

and Electronic Physics, Vol. 3, No 1, (2011), PP.185-192.

[26] B. Cullity and S. Stock, “Elements of X-ray Diffraction,” 3nd

Edition,

Prentice Hall, New York (2001).

[27] L. Freund and S. Suresh, “Thin Film Materials, Stress, Defect Formation

and Surface Evolution,” 1st Edition, Massachusetts Institute of Technology,

(2003).

[28] C. Barred and T. Massalski, “Structure of Metals,” Pergamum Press,

Oxford, (1980), 204.


152

[29] M. Hassan, A. Haseeb, R. Saidur and H. Masjuki, “Effects of Annealing

Treatment on Optical Properties of Anatase TiO2 Thin Films,” World

Academy of Science, Engineering and Technology, Vol. 40, (2008), PP.

221-225.

[30] L. Hsu and D. Luca, “Substrate and Annealing Effects on the Pulsed-

Laser Deposited TiO2 Thin Films,” Journal of Optoelectronics and

Advanced Materials, Vol. 5, No. 4, (2003), PP. 841-847.

[31] S. Karvinen, “The Effect of Trace Element Doping of TiO2 on the Crystal

Growth and on the Anatase to rutile Phase Transformation of TiO2,” Solid

State Sciences, Vol. 5, (2003), PP. 811-819.

[32] M. Brodsky, “Amorphous Semiconductors,” Sepringer-Verlag, Berlin,

Heidelberg, (1979).

[33] S. Sankar and K. Gopchandran, “Effect of Annealing on the Structural,

Electrical and Optical Properties of Nnanostructured TiO2 Thin Films,”

Crystal Research Technology, Vol. 44, (2009), PP. 989-994.

[34] A. Adnan Hateef, “Studying the Optical and Electrical Properties of (TiO2)

Thin Films Prepared by Chemical Spray Pyrolysis Technique and their

Application in Solar Cells,” M.Sc. Thesis, Al-Mustansiriyah University

College of Science Department of Physics, (2010), P. 70.


153

Table 1: Lattice constants and interpllanar spacing of TiO2.

Table 2: The obtained result of the structural properties from XRD for TiO2 thin films.

Temperature ( oC)

degree) (hkl)

Interplanar

spacing, d Å

Lattice constant Å

a c c/a

As-deposited at 300 25.27 A(101) 3.15 3.3439 /

2.842 37.83 A(004) 2.37 / 9.5050

400

25.2 A(101) 3.53 3.8 /

3.502 37.81 A(004) 2.37 / 9.5098

48.1 A(200) 1.89 3.7803 /

500

25.17 A(101) 3.53 3.8 /

3.503 37.79 A(004) 2.38 / 9.5147

48.12 A(200) 1.89 3.7788 /

27.47 R(110) 3.24 4.5881 / /

600

25.11 A(101) 3.54 3.8170 /

2.497 37.72 A(004) 2.38 / 9.5317

48 A(200) 1.89 3.7877 /

27.41 R(110) 3.25 4.5979 / 0.641

54.35 R(211) 1.68 / 2.9484

Temperature ( oC)

degree) (hkl)

Stress Ss

(GPa)

Strain δ

10-3)) FWHM°

Main

Grain

Size (nm)

Texture Tc

As-deposited at

300

25.27 A(101) 0.218 0.9354

0.450 19.02 1.813

37.83 A(004) 0.440 19.94

400

25.2 A(101)

0.098 0.4225

0.421 20.19

1.126 37.81 A(004) 0.412 21.27

48.1 A(200) 0.410 22.16

500

25.17 A(101)

-0.019 0.084

0.352 24.16

1.154 37.79 A(004) 0.400 21.94

48.12 A(200) 0.349 25.99

27.47 R(110) 0.334 25.59

600

25.11 A(101)

-0.435 1.8709

0.301 28.25

0.952

37.72 A(004) 0.288 30.43

48 A(200) 0.338 26.88

27.41 R(110) 0.849 3.640

0.315 27.13

54.35 R(211) 0.293 31.85


154

Table 3: Morphological characteristics from AFM images for TiO2 thin film

Table 4: Shows allowed direct band gap and allowed indirect band gap for TiO2 thin film

Temperature oC

Roughness average

(nm)

Root Mean Square (RMS)

(nm)

As-deposited at 300 46.5 60.5

400 76.6 95

500 84.3 105

600 88.6 114

Temperature (oC)

Allowed direct band

gap (eV)

Allowed indirect band

gap (eV)

As-deposited at 300 3.74 3.49

400 3.7 3.39

500 3.68 3.35

600 3.55 3.1


155

Fig. 1: XRD patterns of TiO2 films deposited at 300 °C temperature and annealed at 400

°C, 500 °C and 600 °C

a

b


156

Fig. 2: 2D and 3D AFM images of TiO2 films deposited at 300 °C temperature and

annealed: (a) As-deposited, (b) 400 °C, (c) 500 °C and (d) 600 °C.

c

d


157

Fig. 3: The optical transmission of TiO2 thin films deposited at 300 °C temperature and

annealed at 400 °C, 500 °C and 600 °C

Fig. 4: Absorption coefficient as a function of wavelength for the TiO2 thin films at

different annealing temperatures.


158

Fig. 5: Allowed direct electronic transitions of TiO2 thin films at different annealing temperatures


159

Fig. 6: Allowed indirect electronic transitions of TiO2 thin films at different annealing temperatures.

Fig. 7: Refractive index as a function of wavelength for the TiO2 thin films at different annealing

temperatures.

Fig. 8: Extinction Coefficient as a function of wavelength for the TiO2 thin films at different

annealing temperatures.


160

Fig. (4.14): Real (Ԑr) parts of the dielectric function as a function of wavelength for the TiO2 thin films at


Fig. (4.15): Imaginary (Ԑi) parts of the dielectric function as a function of wavelength for the TiO2 thin films at
