Microelectronic Engineering 163 (2016) 6777

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Microelectronic Engineering
journal homepage: www.elsevier.com/locate/mee

The effect of various oxidation temperatures on structure of Ag-TiO2

thin lm
Shima Khosravani a, Sedigheh Bagheri Dehaghi b, Mohammad Bagher Askari c,, Maedeh Khodadadi d
a

Department of Physics, Islamic Azad University, Karaj Branch, Karaj, Iran

Department of chemistry, University of Isfahan, Po Box 81746-73441, Iran
Department of Physics, Payame Noor University, PO Box 19395-3697, Tehran, Iran
d
Department of Physics, Islamic Azad University, Karaj Branch, Karaj, Iran
b
c

a r t i c l e

i n f o

Article history:
Received 28 December 2015
Received in revised form 18 May 2016
Accepted 9 June 2016
Available online 10 June 2016
Keywords:
Ag nanoparticles
TiO2 thin lm
Oxidation temperatures
Surface morphology
DC magnetron sputtering

a b s t r a c t
In this research, Ag/TiO2 thin lms have been deposited on quartz and silicon (Si) substrates at room temperature. In the rst step, titanium thin lms were deposited on quartz and silicon substrates by electron beam evaporation technique and subsequent annealing under the oxygen ow in the electrical furnace at various
temperatures for preparation of Titanium dioxide (TiO2) thin lms. In the second step, Ag nanolayer was
sputtered on TiO2 thin lms by DC magnetron sputtering technique. The techniques of X-ray diffraction (XRD),
atomic force microscopy (AFM) and scanning electron microscopy (SEM) were applied for characterization of
structural and morphological properties of Ag/TiO2 thin lms deposited on quartz and silicon substrates. The results shows that the structure of TiO2 lms changed from amorphous to crystalline by varying the oxidation temperature, that can effectively inuenced on the surface morphology of Ag-TiO2 thin lms and the size of Ag
nanoparticles.
2016 Elsevier B.V. All rights reserved.

1. Introduction
TiO2 was interested as a pollution control and self-cleaning
material in the past decades. TiO2 has widely used because of its hydrophilicity properties and photocatalysis [1]. TiO2 crystallizes in the Rutile
(Ru), Anatase (An) and Brookite (Br) phases. The Anatase phase has
photocatalytic property. Photocatalysis is a technology for completely
decomposing or eliminating numerous toxic organic pollutants.
Among photocatalysis, TiO2 emerges as an effective substance with relatively no toxicity, chemical stability and low prices [24]. Nevertheless,
TiO2 photocatalyst generates electron and hole pair (e/h+) upon irradiation under UV-light ( b 388 nm) through its wide band gap of 3.2 eV
[58]. Generally, in comparison to the other spectrums of solar light,
UV-light has low intensity. Using TiO2 for indoor air treatment which
is often applied under visible light is a disadvantage. Therefore, many
studies focusing on production of visible light responsive TiO2. Some
studies have demonstrated that decorating TiO2 with silver nanoparticles (Ag) can increase the photocatalytic activity of TiO2 signicantly

Corresponding author.
E-mail address: Mb_askari@yahoo.com (M.B. Askari).

http://dx.doi.org/10.1016/j.mee.2016.06.008
0167-9317/ 2016 Elsevier B.V. All rights reserved.

by increasing the lifetime of e/h+ pairs and reducing energy band

gap from UV to visible-light region [912]. Practically, TiO2 can be
immobilized as a thin lm to avoid recovery of TiO2 after use. The TiO2
thin lm can be coated on various solid substrates such as ceramic tile,
plastics and glass. TiO2 thin lm coated on plastic substrates and can
be made into a wide range of shapes. It has many advantages such as
exibility, simple use, low cost and light weight.
The silver particles in dimension of nanometer increase its
germicidal property more than 99%. Because covering of consumer
equipment with pure silver has high cost, therefore, the use of other
metal materials combined with silver, is a practical way to use the silver
germicidal property. Titanium dioxide-silver coatings due to antibacterial properties of silver and effect self-cleaning of titanium dioxide
use in the operating room and ceramic parts in public places. This
combination has thermal, excellent electrical properties and antibacterial and due to high resistance to corrosion has many applications
in industries such as optics and biomaterials. Ag-TiO2 is produced by
using chemical methods. The chemical methods require the use of
new materials or solvents that may undesirable impurities that are
not environmentally friendly. In this study, physical methods due to
have less pollution to the environment are used. Also the deposition
rate versus chemical methods isn't so mush and incontrollable. The ability to control of the thickness and quality of the suitable coating also

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S. Khosravani et al. / Microelectronic Engineering 163 (2016) 6777

Table 1
Deposition conditions of Ti thin lm on quartz and Si(100) substrates and deposition of Ag
thin lm on TiO2/Si and TiO2/quartz substrates.
Deposition conditions
Substrates
Base pressure (mbar)
Deposition pressure (mbar)
Target-substrate distance (cm)
Current (mA)
Voltage (V)
Deposition time (s)
Power (W)
Film thickness (nm)
Deposition method

Ti lms

Ag lms

Quartz, Si(100)
1 106
2.6 105
5
101
4900
240
495
90
Thermal evaporation

TiO2/Si, TiO2/quartz
6 105
5 102
7
110
150
45
16.5
120
DC magnetron sputtering

there are. In this study, the structural and morphological properties of

silver nanolayer deposited on titanium dioxide prepared at different
temperatures on the silicon and quartz substrates were investigated
[1315].
The advantages of DC magnetron sputtering technique are: This process provides the homogeneous large area coating in the nal products
and favorable deposition has identied, to produce the suitable coatings
parameters. However, Magnetron sputtering technology is very advantageous for decorative coatings (e.g. Ti, Cr, Zr and carbon nitrides), based
on its smooth nature. Otherwise, High Power Impulse Magnetron
Sputtering (HIPIMS) is a PVD (physical vapor deposition) coating technology which has the advantages of both arc technology and magnetron
sputtering. Because, they create a dense sputtered layer with good adhesion, which is also extremely smooth [16].
2. Experimental

Fig. 2. X-ray diffraction pattern of silver layers accumulated on titanium dioxide on quartz
substrate.

crystal mass monitor, the lms thickness measured in the chamber.

Then titanium thin lms were oxidized in the electrical furnace under
oxygen ow at temperatures of 400, 500, 600, 700 and 800 C for 3 h.
The XRD analysis was used for determining crystallographic structures
of thin lms of titanium dioxide. Then by using the target of silver and
DC magnetron sputtering method, Ag nanolayer was deposited on titanium dioxide lms. The deposition conditions of Ti and Ag thin lms are
shown in Table 1 [17].

In this study, quartz and Si substrates (1 cm 1 cm) were used. The

chemical pretreatment of substrates was carried out with acetone and
propanol successively in ultrasonic bath for 10 min. After drying in N2
gas ow, they were introduced into the chamber. Then, a thin layer of
titanium deposited on quartz and Si substrates by means of thermal
evaporation method with using titanium powder 99/99%. By quartz

3. Results & discussion

Fig. 1. X-ray diffraction pattern of TiO2 layer produced by oxidation at temperatures 400,
500, 600, 700, and 800 C on quartz substrate.

Fig. 3. X-ray diffraction pattern of TiO2 layer produced by oxidation at temperatures 400,
500, 600, 700, and 800 C on silicon substrate.

3.1. XRD analysis

Fig. 1 shows XRD patterns of Ti layers deposited on quartz substrates
by thermal evaporation method and then oxidized at temperatures 400,

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69

intensity of peaks increases by increasing oxidation temperature. At oxidation temperatures of 600, 700 and 800 C, the crystalline structures
of titanium dioxide are formed in the rutile phase with (110), (101)
and (211) orientations [18].
The X-ray diffraction patterns of Ag layers accumulated on quartz/
TiO2 by using DC magnetron sputtering method are shown in Fig. 2.
In all samples, the peaks of crystalline pages (111), (200) and (220)
formed that all these peaks belong to the cubic structure of silver.
At oxidation temperatures of 700 and 800 C, there are the peaks
related to the crystalline structures of TiO2 in directions of (110) and
(211), too.
Fig. 3 shows X-ray diffraction patterns of titanium layers deposited
on Si substrate by thermal evaporation method by electron beam and
then oxidized at temperatures of 400, 500, 600, 700 and 800 C. At temperature of 400 C, the crystalline structure isn't formed.
At oxidation temperatures of 500 C, the crystalline structures of
titanium dioxide are formed in the Brookite phase with (021) orientation. At temperature of 600 C, there is both Brookite and Rutile phase.
At 700 C, also Brookite and Rutile phases with crystalline plates
Ru(020), Br(110), Ru(200), Ru(210) and Ru(211) are formed. The
sample with oxidation temperatures of 800 C almost behaves like
700 C. In this temperature, the crystalline structures in directions of
Ru(020), Br(410), Ru(110), Ru(101), Ru(200), Ru(210) and Ru(211)
are formed.
The X-ray diffraction patterns for Ag layers accumulated on Si/TiO2
substrate by means of DC magnetron sputtering method are shown in
Fig. 4. In all samples, there are peaks corresponding to crystalline plates
(111) and (200) related to the cubic structure of silver. At temperatures
of 500, 600, 700 and 800 C, in addition to silver peak, peaks corresponding to the Brookite phase (021) are formed. At temperatures of 600, 700
and 800 C, in addition to Brookite phase, rutile phase in directions of

Fig. 4. X-ray diffraction pattern of silver layers accumulated on titanium dioxide on silicon
substrate.

500, 600, 700 and 800 C. In the samples of oxidized at temperatures of

400 and 500 C, except peak of quartz substrate is not observed another
peak. This indicates that the layer is amorphous and crystalline structures aren't created. From temperature of 600 C, peaks observed and

Table 2
The average size of crystalline TiO2 and Ag on quartz substrate.

Quartz/TiO2

Quartz/TiO2/Ag

Oxidation temperature of Ti layers (C)

2
(deg)

2
(JCPDS) (deg)

Peak density

FWHM

Crystalline page

D
(nm)

400
500
600
700
800
400
500
600
700
800

32.06
32.816
32.813
44.56
44.60
44.56
44.37
44.61

32.527
32.527
32.527
44.666
44.666
44.666
44.666
44.666

46.74
14.24
23.08
79.75
66.80
64.49
42.37
83.84

0.17
0.15
0.10
0.38
0.37
0.31
0.27
0.24

Ru(110)
Ru(110)
Ru(110)
(111)
(111)
(111)
(111)
(111)

66.5
66.9
99.9
27.2
28.0
34.4
38.3
43.1

Table 3
The average size of crystalline TiO2 and Ag on Si substrate.

Si/TiO2

Si/TiO2/Ag

Oxidation temperature of Ti layers (C)

2
(deg)

2
(JCPDS) (deg)

Peak density

FWHM

Crystalline page

D
(nm)

400
500
600
700
800
400
500
600
700
800

43.61
32.05
32.08
32.06
44.45
44.99
44.81
44.17
43.73

43.416
32.527
32.527
32.527
44.666
44.666
44.666
44.666
44.666

36.24
10.91
30.47
35.32
45.94
9.10
33.80
11.70
8.16

0.47
0.45
0.29
0.13
0.34
0.26
0.24
0.21
0.20

Br(021)
Ru(111)
Ru(111)
Ru(111)
(111)
(111)
(111)
(111)
(111)

21.9
22.1
34.3
76.7
30.4
39.9
43.2
49.2
51.6

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Fig. 5. Three-dimensional AFM images of silver accumulated on a layer of titanium oxide by means of DC magnetron sputtering method at oxidation temperatures A) 400 C, B) 500 C, C)
600 C, D) 700 C and E) 800 C with a quartz substrate.

(110), (211) and (200) also are formed. At temperatures of 800 C, the
Br(410) and Ru(200) peaks related to titanium dioxide are also
observable.
The XRD analysis revealed that after oxidation of titanium substrates
at different temperatures, the crystalline phases of TiO2 in quartz

substrate at temperatures above of 600 C and silicon substrate at temperatures above of 500 C has been formed. Also, by increasing oxidation temperature, the property of TiO2 crystalline increased. An
average size of crystals was calculated by using Scherrer equation. The
results indicate that by increasing oxidation temperature of titanium

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71

Fig. 6. Three-dimensional AFM images of silver accumulated on a layer of titanium dioxide by means of DC magnetron sputtering method at temperatures A) 400 C, B) 500 C, C) 600 C, D)
700 C and E) 800 C with silicon substrate.

layer, the average size of TiO2 crystal increased. This could be cause of an
increase in the average size of the crystalline grains of silver accumulated on TiO2 layer. Tables 2 and 3 show average size of TiO2 and silver

crystals on quartz and Si substrate. In Tables 2 and 3, JCPDS and

FWHM are respectively joint committee on powder diffraction standards and full width at half maximum.

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Table 4
Result of AFM analysis (RMS roughness and average roughness) and SEM analysis (grain size of Ag) of silver nanolayer deposited on TiO2.
Titanium oxidation
temperature (C)

Substrate

RMS rough (nm)

Ave. rough (nm)

Silver grain size using

SEM analysis

400
500
600
700
800
400
500
600
700
800

Quartz
Quartz
Quartz
Quartz
Quartz
Si
Si
Si
Si
Si

1.78
6.02
7.19
7.34
7.62
2.14
4.93
6.33
7.62
13.36

1. 45
4.69
5.73
5.81
5.99
1.65
3.97
5.00
6.06
10.67

7.92
17.45
22.70
30.89
35.53
7.84
16.21
17.93
24.41
25.78

3.2. AFM analysis

The AFM analysis was used for a detailed study of the surface morphology and distribution of crystalline silver on TiO2 layer. Figs. 5 and
6 show three-dimensional AFM images of Ag layer accumulated on
TiO2 on quartz and Si substrates. By increasing oxidation temperature
of titanium layer, surface roughness of Ag increases. In both 400 and
500 C samples with both quartz and Si substrates, crystalline structure
is aciform. In 600 C sample with Si substrate, surface morphology is still
aciform but with quartz substrate, surface morphology has been conical.
At temperature of 700 C in both substrates, the surface structure is conical. Finally, at 800 C for both substrates, the surface morphology has
been like pile. Fig. 5 and 6 three-dimensional AFM images of Ag layers
accumulated [19].

3.3. SEM analysis

The SEM analysis is used to determination of the grain size of the silver nanoparticles on TiO2 layer at different temperatures. The size of silver nanoparticles deposited on prepared at different temperatures on
silicon and quartz substrate collected in Table 4. These results obtained
with calculation of the average size of 50 grain at each temperature. The
root mean square roughness (RMS rough) and average roughness (ave.
rough) obtained from SEM analysis are in the Table 4, too. By increasing

oxidation temperature of titanium, silver nanoparticles been larger and

root mean square roughness and average roughness increases, which is
in agreement with AFM analysis (Fig. 7). Figs. 8, 9 and 10, 11 show SEM
images and abundance of Ag nanoparticles accumulated on TiO2 on
quartz and Si substrates [20].

4. Conclusion
In this study, silver nanolayers were accumulated on TiO2 layers on
quartz and silicon substrate by using DC magnetron sputtering method
in different temperatures. The XRD analysis revealed that by increasing
oxidation temperature of titanium, TiO2 layer structure changed from
amorphous to a crystalline state. This change for quartz substrate was
from the amorphous to the Rutile crystalline structure and for silicon
substrate to Brookite and Rutile crystalline structure. Also in both substrates, by increasing oxidation temperature, the average size of TiO2
crystals and average size of silver crystals accumulated on TiO2 in direction (111) increase. AFM analysis also revealed that the surface roughness and particles size of silver also increased. The SEM analysis also
clearly showed increasing the size of the silver particles that are in
good agreement with XRD and AFM analyses. TiO2 modied by Ag
nanoparticles has photocatalytic and antimicrobial applications. Also
Ag/TiO2 thin lm has the potential to be applied in indoor air pollution
treatments and self-cleaning processes.

Fig. 7. RMS rough and ave. rough and silver grain size on TiO2 deposited on quartz (A) and Si (B) substrate vs oxidation temperature.

S. Khosravani et al. / Microelectronic Engineering 163 (2016) 6777

Fig. 8. SEM images of Ag nanoparticles accumulated on TiO2 on quartz substrate at temperatures of A) 400, B) 500, C) 600, D) 700 and E) 800 C.

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S. Khosravani et al. / Microelectronic Engineering 163 (2016) 6777

Fig. 9. Abundance of Ag nanoparticles accumulated on TiO2 on quartz substrate at temperatures of A) 400, B) 500, C) 600, D) 700 and E) 800 C.

S. Khosravani et al. / Microelectronic Engineering 163 (2016) 6777

Fig. 10. SEM images of Ag nanoparticles accumulated on TiO2 on silicon substrate at temperatures of A) 400, B) 500, C) 600, D) 700 and E) 800 C.

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S. Khosravani et al. / Microelectronic Engineering 163 (2016) 6777

Fig. 11. Abundance of Ag nanoparticles accumulated on TiO2 on silicon substrate at temperatures of A) 400, B) 500, C) 600, D) 700 and E) 800 C.

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