Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition

UNIVERSITY OF
TECHNOLOGY
A thesis submitted By
Khaled Z.Yahya

PLD: Pulsed Laser Deposition
The interaction of the laser beam with
the target resulting in evaporation of the
surface layers.
The interaction of the laser beam with the
evaporation materials causing the formation of
isothermal expanding plasma.
The expansion of the laser induced plasma
with a rapid transfer of thermal energy of the
species in plasma into kinetic energy.
Thin film growth.

Rotating target
Laser
Pulsed
Substrate
heater
Ejected Plume
Deposited
film

Why TiO2 ?
Titanium dioxide (TiO2) is a wide band gap ( ) eV for anatase and 3 eV
for rutile .
Titanium dioxide have high refractive index - up to 2.7 (at wavelength of
600nm)
Titanium dioxide good chemical resistance and high chemical stability.
Titanium dioxide good sensitivity to poison gases.
Titanium dioxide good photocatalysts.

TiO2 structure
Anatase Rutile Brockets

TiO2 gas sensor
• TiO2 based sensor are predominant solid-state
gas sensors for domestic, commercial and
industrial application.
• •Low cost
• •Easy production
• •Rigid construction
• •Compact size
• •Simple measuring electronics

Aim of the work
The aim of this work is to reveal specific properties of TiO2
nanostructure prepared by pulsed laser deposition technique
TiO2 samples have been prepared at different dopant noble
metal such as (Pd ,Pt, Ni, Ag,…) The main objective of this
work are :
• 1. Characteristics of structural , microstructural and
photoluminescence properties of thin films .
• 2. Studying the sensitivity and selectivity of these films doped
with different noble metal deposited by PLD to CO gas.

Prepared TiO2
Picture for TiO2 ceramic

Characterization Measurements of
prepare films
Films thickness measurement
XRD Study
TCO film Morphology SEM ,AFM
Optical properties
photoluminescence properties
Gas sensor measurement

a)SEM b)AFM c)PL d)Gas sensing
c d
a ba b

•Substrate Temperatures effect (Ts )
c
b
a
2θ (degree)
A :anatase
Figure (1) XRD spectra of TiO2/glass at different temperature
a) 200ºC b) 300ºC, c)400ºC
Intensity
(a.u)
laser fluence 0.8 J/cm2 oxygen
pressure 5 *10-1 Torr

FWHM and Main grain size
0
10
20
30
40
50
250 300 350 400 450 500 550
Temperature °C
Maingrainsize(nm)
0.42
0.43
0.44
0.45
0.46
0.47
0.48
0.49
0.5
0.51
250 300 350 400 450 500 550
Temperature °C
FWHM°
a b
Figure (3) TiO2 A(101) thin films grown
on Si (111) at different substrate temperature for (a) main grain size (b)FWHM

Oxygen pressure effect
Fig (4) XRD patterns of TiO2 films grown on Si
at various oxygen pressures a) 5×10-2 Torr b) 5×10-1 Torr c) 10 Torr
Intens
ity
(a.u)
2θ (degree)

Laser Fluence effect
Fig (5) XRD patterns of TiO2 films grown on Si
at various laser fluence a) 1.2 b) 0.8 c) 1.8 J/cm2

Doping effect of noble metal
(Ag, Pt, Pd and Ni).

X - ray Florescence
Fig (7) X-ray florescence pattern for a) TiO2 pure b) TiO2 3% Ag c) TiO2 3% Pt d) TiO2 3% Pd e) TiO2 3% Ni .
a
b

SEM
Substrate Temperatures effect (Ts )
Figure (8) SEM image of the TiO2/Si thin films deposited at various temperature of
a) 300°C, b) 400°C, c) 500°C, and laser fluence 1.2 J/cm2 ,O2 pressure=
10-1 mbar

Oxygen pressure effect
c
ba
Figure (9) SEM image of the TiO2/Si thin films deposited at various
oxygen pressure a ) 5×10-2 mbar, b) 5×10-1 mbar and c) 10 mbar at
substrate temperature 500 °C
and laser fluence 1.2 J/cm2

Doping effect of noble metal (Ag, Pt, Pd and
Ni).
a
c
b
d
Figure (10) SEM image of the TiO2/Si thin films doping 3% with different noble
metal a) Ag b) Pt c) Pd and d) Ni

SEM of plane grain size (nm)X-ray of plane grain size (nm)sample
2931TiO2 Pure 300°C
3536.3TiO2 Pure 400°C
4041.28TiO2 Pure 500°C
Table (1). The grain size of the TiO2 films
SEM of plane grain size (nm)X-ray of plane grain size (nm)O2 Pressure (mbar)sample
33345×10-2TiO2/Si
39415×10-1TiO2/Si
343610TiO2/Si
SEM of plane grain size (nm)X-ray of plane grain size
(nm)
Dopants atom Radii
(pm)
sample
1515.7126TiO23Ag
1111.6130TiO23Pt
2021.572TiO2Pd 3
181969TiO2Ni 3

Atomic Force Microscopy (AFM)
Substrate
Temperatures effe
(TS)
Figure (11) AFM image of the TiO2/Si thin films deposited at various substrate temperature of
a) 300 C, b) 400 C, c) 500 C, and laser fluence 1.2 J/cm2 ,O2 pressure=10-1 mbar

Oxygen Pressure effect
Figure (12) AFM image of the TiO2/Si thin
films deposited at various oxygen pressure
a ) 5×10-2 mbar, b ) 5×10-1 mbar and c) 10
mbar at substrate temperature 500 °C
and laser fluence 1.2 J/cm2

doping effect of noble metal (Ag ,Pt
,Pd ,and Ni)
b
c
d
a
Figure (13) AFM image of the TiO2/Si thin
films doping 3% with different noble metal a)
Ag b) Pt c) Pd and d) Ni substrate
temperature 500 °C
and laser fluence 1.2 J/cm2 with O2
pressure=10-1 mbar.

Table (2). The RMS and roughness of TiO2 films
from AFM
RMS roughness(nm)AFM of plane grain size (nm)X-ray of plane grain size(nm)sample
2.13031TiO2 Pure 300°C
434.436.3TiO2 Pure 400°C
11.24241.28TiO2 Pure 500°C
RMS
roughness
AFM of plane grain size (nm)X-ray of plane grain size (nm)(O2) Pressure mbarsample
4 (nm)32345×10-2TiO2/Si
6 nm40415×10-1TiO2/Si
16.7nm333610TiO2/Si
RMS roughnessAFM of plane grain size (nm)X-ray of plane grain size (nm)sample
26 nm1615.7TiO2 :3% Ag
28 nm12.411.6TiO2 :3% Pt
23 nm2321.5TiO2 :3% Pd
24 nm20.519TiO2 :3% Ni

Optical Properties
Transmission
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000
Wave length (nm)
T(%)
TiO2 400 C
TiO2 300 C
TiO2 200 C
Substrate Temperatures effect (TS)
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000
Wave length (nm)
T(%)
10 mbar
10 -2 mbar
10 -1 mbar
Oxygen Pressure effect
0
10
20
30
40
50
60
70
80
90
0 200 400 600 800 1000
Wave length (nm)
T(%)
0.8 J/cm2
1.8 J/cm2
1.2 J/cm2
Laser Fluence effect
0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000
Wave length (nm)
Transmtance%
TiO2 :3% Ag
TiO2 :3% Pd
TiO2 :3%Ni
TiO2 :3% Pt
TiO2 Pure
Doping effect of noble metal (Ag, Pt, Pd and Ni).

Optical Energy Gap Eg
°
Substrate Temperatures effect (Ts )

doping effect of noble metal (Ag ,Pt ,Pd ,and Ni)
direct Eg

Indirect Eg

Table (3) Physical and optical measurements for pure
and doped TiO2 films
Optical energy gab E°g (eV)
(indirect)
Optical energy gab E°g (eV)
(direct)
Samples
3.033.4TiO2 Pure at 200 °C
3.13.5TiO2 Pure at 300 °C
3.23.6TiO2 Pure at 400 °C
3.123.42TiO2:1%Ag at 200 °C
3.203.5TiO2 :2%Ag at 200 °C
3.283.67TiO2 :3%Ag at 200 °C
3.113.41TiO2 :1%Pt at 200 °C
3.193.52TiO2 :2%Pt at 200 °C
3.253.58TiO2 :3%Pt at 200 °C
2.933.42TiO2:1%Pd at 200 °C
2.93.37TiO2 :2%Pd at 200 °C
2.883.32TiO2 :3%Pd at 200 °C
2.943.42TiO2:1%Ni at 200 °C
2.93.38TiO2 :2%Ni at 200 °C
2.83.35TiO2 :3%Ni at 200 °C

Refractive index (n)
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
hv (eV)
Refractiveindex(n)
TiO2 400 C
TiO2 300 C
TiO2 200 C
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4 5
hv (eV)
Refractiveindex(n)
TiO2 Pure
TiO2 :1%Ag
TiO2 :2% Ag
TiO2 :3%Ag
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4 5
hv (eV)
Refractiveindex(n)
TiO2 Pure
TiO2 :1% Pt
TiO2 :2% Pt
TiO2 :3%Pt
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
hv (eV)
Refractiveindex(n)
TiO2 Pure
TiO2 :3% Pd
TiO2 :2% Pd
TiO2 :1% Pd
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
hv (eV)
Refractiveindex(n)
TiO2 Pure
TiO2 :3% Ni
TiO2 :2%Ni
TiO2 :1% Ni

0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5
hv (eV)
extinctioncoefficient(K)
TiO2 :3% Ag
TiO2 :2% Ag
TiO2 :1% Ag
TiO2 Pure
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5
hv (eV)extinctioncoefficient(K)
TiO2 :3%Pt
TiO2 :2%Pt
TiO2 :1%Pt
TiO2 pure
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5
hv (eV)
TiO2 Pure
TiO2 :1%Pd
TiO2 :2%Pd
TiO2 :3%Pd
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5
hv (eV)
TiO2 Pure
TiO2 :1%Ni
TiO2 :2%Ni
TiO2 :3%Ni
Extinction Coefficient
0
0.05
0.1
0.15
0.2
0.25
0.3
0 1 2 3 4 5
hv (eV)
TiO2 200 C
TiO2 300 C
TiO2 400 C

Photoluminescence (PL)
Substrate Temperature effect (Ts)
c
a b
Figure (23) Photoluminescence spectrum of pure TiO2/glass thin films deposited at various substrate temperature of
a) 300°C, b) 350 °C, c) 400°C, and laser fluence 1.2 J/cm2 ,O2 pressure=10-1 mbar

The doping effect of noble metals (Ag ,Pt ,Pd ,and Ni)
a b
c d
Figure (24) Photoluminescence spectrum of the TiO2/glass thin films doping 3% with different noble metal a) Ag b) Pt c) Pd
and d) Ni ,at substrate temperature 400 °C
and laser fluence 1.2 J/cm2 with O2 pressure=10-1 mbar.

Table (4) Energy values and Intensity of PL Peaks
Samples Energy of Peak
A (eV)
Intensity (a.u) Energy of Peak B (eV) Intensity (a.u) Optical energy
gap (eV) E°
g
TiO2 at 300°C 3.06 840 2.39 365 3.03
TiO2 at 350°C 3.12 900 2.4 390 3.1
TiO2 at 400°C 3.22 1000 2.43 415 3.2
TiO2 :3% Ag at
400°C
3.24 280 2.45 150 3.28
TiO2 :3% Pt at
400°C
3.25 540 2.5 380 3.25
TiO2 :3% Pd at
400°C
2.93 810 2.33 350 2.88
TiO2 :3% Ni at
400°C
2.85 820 2.3 400 2.8

Sensing properties
Room Temperature
0
0.02
0.04
0.06
0.08
0.1
0.12
0 200 400 600 800 1000
Time (sec)
Sensetivity
TiO2 Pure
TiO2:3%Pt
TiO2:3%Ag
TiO2:3%Pd
TiO2:3%Ni
Figure (24) Sensitivity for TiO2/glass pure and doping with a )Ag b)Pt c) Pd
d) Ni as a function of operation time for CO gas at Room temperature and
laser fluence 1.2 J/cm2 with O2 pressure=10-1 mbar

Operation time Effect on sensing properties
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 100 200 300 400 500 600 700 800 900
Time (sec)
Sensitivity
TiO2 Pure
TiO2 :1% Ag
TiO2 :2% Ag
TiO2 :3% Ag
0
0.5
1
1.5
2
2.5
3
3.5
0 100 200 300 400 500 600 700 800 900
Time (sec)
Sensitivity
TiO2 Pure
TiO2 :1% Pt
TiO2 :2% Pt
TiO2 :3% Pt
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500 600 700 800 900
Time (sec)
Sensitivity
TiO2 Pure
TiO2 :1% Pd
TiO2 :2% Pd
TiO2 :3% Pd
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 100 200 300 400 500 600 700 800 900
Time (sec)
Sensitivity
TiO2 Pure
TiO2 :1% Ni
TiO2 :2%Ni
TiO2 :3% Ni
a b
d
c
Figure (25) Sensitivity for TiO2/glass pure and doping with a )Ag b)Pt c) Pd d)
Ni as a function of operation time for CO gas at operation temperature 250 C and
laser fluence 1.2 J/cm2 with O2 pressure=10-1 mbar

Operation time Effect on resistance properties
0
2
4
6
8
10
12
0 200 400 600 800 1000
Time (sec)
Resistance(ohm)*10^9
TiO2 Pure
TiO2 :1% Ag
TiO2 :2% Ag
TiO2 :3% Ag
0
2
4
6
8
10
12
0 200 400 600 800 1000
Time (sec)
TiO2 Pure
TiO2 :1% Pt
TiO2 :2% Pt
TiO2 :3% Pt
0
2
4
6
8
10
12
0 200 400 600 800 1000
Time (sec)
TiO2 Pure
TiO2 :1% Pd
TiO2 :2% Pd
TiO2 :3% Pd
0
2
4
6
8
10
12
0 200 400 600 800 1000
Time (sec)
TiO2 Pure
TiO2 :1% Ni
TiO2 :2% Ni
TiO2 :3% Ni
Figure (26) resistance for TiO2/glass pure and doping with a )Ag b)Pt c)
Pd d) Ni as a function of operation time for CO gas at operation
temperature 250 C and laser fluence 1.2 J/cm2 with O2 pressure=10-1
mbar
a b
c
d

Operation time Effect on current properties
0
1
2
3
4
5
6
7
8
0 200 400 600 800 1000
Time (Sec)
current(nA)
TiO2 pure
TiO2 1% Ag
TiO2 2% Ag
TiO2 3% Ag
0
1
2
3
4
5
6
7
8
9
10
0 200 400 600 800 1000
Time (Sec)
current(nA)
TiO2 pure
TiO2 1%Pt
TiO2 2%Pt
TiO2 3%Pt
0
1
2
3
4
5
6
7
0 200 400 600 800 1000
Time (Sec)
current(nA)
TiO2 pure
TiO2 1% Pd
TiO2 2% Pd
TiO2 3%Pd
0
1
2
3
4
5
6
0 200 400 600 800 1000
Time (Sec)
current(nA)
TiO2 pure
TiO2 1% Ni
TiO2 2% Ni
TiO2 3% Ni
a
d
c
b
Figure (27) current for TiO2 /glass pure and doping with a )Ag
b)Pt c) Pd d) Ni as a function of operation time for CO gas at
operation temperature 250 C and laser fluence 1.2 J/cm2 with O2
pressure=10-1 mbar

Operation temperature Effect on sensing properties
0
0.5
1
1.5
2
2.5
3
0 50 100 150 200 250 300 350 400 450
T(C)
Sensitivity
TiO2 Pure
TiO2 :2% Ag
TiO2 :3% Ag
TiO2 :1% Ag
0
0.5
1
1.5
2
2.5
3
3.5
4
0 50 100 150 200 250 300 350 400 450
T(C)
Sensitivity
TiO2 Pure
TiO2 :2% Pt
TiO2 :3% Pt
TiO2 :1% Pt
0
0.5
1
1.5
2
2.5
0 50 100 150 200 250 300 350 400 450
T(C)
Sensitivity
TiO2 Pure
TiO2 :2% Pd
TiO2 :3% Pd
TiO2 :1% Pd
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 50 100 150 200 250 300 350 400 450
T(C)
Sensitivity
TiO2 Pure
TiO2 :2% Ni
TiO2 :3%Ni
TiO2 :1% Ni
Figure (28) Sensitivity for TiO2/glass pure and doping with 1% ,2%
and 3% (Ag ,Pt ,Pd ,and Ni) films for CO gas at different operation
temperature and laser fluence 1.2 J/cm2 with O2 pressure=10-1 mbar
a b
c d

Sensitivity of TiO2 /Si
0
5
10
15
20
25
0 100 200 300 400 500
T (C)
Sensitivity
TiO2 Pure
TiO2:3% NI
TiO2:3% Pd
TiO2:3% Ag
TiO2:3%Pt
Figure (29) Sensitivity for TiO2/Si pure and doping with 3% (Ag ,Pt ,Pd ,and Ni) films for
CO gas at different operation temperature at laser fluence 1.2 J/cm2 with O2 pressure=10-
1 mbar

Table (5) Sensitivity values of TiO2 pure and doping with different
noble metal concentration at operation temperature T= 250 °C.
Samples Sensitivity
TiO2 pure/glass 0.5
TiO2 :1% Ag /glass 1.7
TiO2 :2% Ag/glass 2.3
TiO2 :3% Ag/glass 2.7
TiO2 :1% Pt/glass 2.2
TiO2 :2% Pt/glass 3
TiO2 :3% Pt/glass 3.3
TiO2 :1% Pd/glass 1.5
TiO2 :1% Ni/glass 0.85
TiO2 pure/Si 7.5
TiO2 :3% Ag/ Si 17
TiO2 :3% Pt/ Si 23
TiO2 :3% Pd/ Si 15
TiO2 :3% Ni/ Si 12.5

The results in this work agreement with
other results as shown in table below :
References Metal dopantTiO2 Selectivity Sensitivity
[46] - CO 2
[136] - CO 4
[45] - Ethanol and methanol vapor 5
[30] Pt CO 20
[39] Pd CO , H2 4 , 2.5
[81] Nb CO 14
[this work] Pt CO 23
Ag CO 17
Pd CO 14
Ni CO 11
- CO 7.5

Conclusion
Pure TiO2 showed poor response to CO gas.
3 % wt Ag ,Pt ,Pd and Ni doped TiO2 thin film was the
most sensitive element to CO gas .
The optimum operating temperature for CO gas
sensing was (250) °C .
 Ag ,Pt ,Pd and Ni doped TiO2 thin film would be
suitable for fabricating the CO gas sensors.
The sensor TiO2 doping with Pt showed good
selectivity to CO gas.
TiO2 deposited on silicon has sensitivity to CO gas
higher than TiO2 deposited on glass

Future Work
• 1- Studying (TiO2) films as
antireflection coating on (p-n)
junction solar cells and as a
photocatalyst .
• 2- Using a mixing of background gas
N2 + O2 with high vacuum to
enhancement the quality of the films.
• 3- Studying (TiO2) films as a gas
sensor for NO2 and H2 gas .

Paper accepted
1- “Structural and optical properties of TiO 2 photocatalyst thin
film produced by PLD”.
Iraqi Journal science 3rd Scientific conference Baghdad University.
2- "Investigation of structural and Morphology properties of
Nanocrystalline thin films prepared by PLD ".
Journal of the collage education in the 6th conference on physics .
Paper submitted
3-" Structure and Morphology properties of nanocrystalline
noble metal doped films for gas sensing properties "
-2nd conference of nano technology and advance material and their
application .
4-" Nanostructure dopants TiO2 films for gas sensing".
Iraqi Journal of applied physics .

Characterization of different dopants in TiO2 Structure by Pulsed Laser Deposition

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