INTRODUCTION

In recent years, perovskite structure compounds, especially ABO
3
(A = Sr, Ba,
Pb, Ca and B = Ti, Zr) have been paid attention and researched popularly
because of their great applications in technology and practicality. ABO
3
materials have interesting characters, such as optical, ferroelectric and
piezoelectric responses and others. Therefore, these materials have been applied
to make capacitor, rheostat, photoelectrodes, ferroelectric storage, gas sensor.
In group of ABO
3
materials, one of the most researched materials is
dielectric Strontium titanate, SrTiO
3
(STO), especially after their ferroelectric
responses were investigated. Because of high dielectric constant, which
increases as freezing and has low short-wave loss, this material is applied in
devices with high frequency, short-wave, even at low temperature. There are
many researches on STO focusing on Ti or Sr doping or replacing with metal
ions to investigate the distortion of perfect cubic structure that causes
interesting physical phenomena.
In the report about doping Sr in SrTiO
3
, it was shown that replacing
metallic ions for Sr position caused the suppression of paraelectric state.
Substitution of Bi for Sr leads to the occurrence of several polarization modes
and phase transition to ferroelectric behavior. La doping in STO materials
strongly suppresses the paraelectric state, without the occurrence of intrinsic
polarization modes, except for polarization effects related to oxygen vacancies.

do not systematic, specially on the effect of transitional metals Fe, Co, Ni on
electromagnetic responses and optical responses of SrTi
1-x
M
x
O
3.
STO materials doped with transition metal (Fe, Co, Ni) are not only
interesting and complicated research object on material science, but also
promising ones in application in Spin electronics, Diluted Magnetic
Semiconductor (DMS). Basing on practical situation and research condition
such as experimental devices, references, research ability and research groups
in Vietnam and abroad the following study and solutions to unsolved
problems are feasible and may give good results.
Therefore, we chose the topic of thesis: "Preparation of SrTi
1-x
M
x
O
3
(M
= Fe, Co, Ni) system and investigation some their properties"
The purpose of thesis is: (i) Preparation of SrTi
1-x
M
x
O
3
(M = Fe, Co, Ni)
systems by sol-gel and Pulsed Laser Deposition (PLD) method. (ii)

substitution on structure, electromagnetic and optical properties of SrTi
1-x
M
x
O
3

samples synthesized by Sol-gel and PLD method
Composition of the thesis: the thesis consists of 140 pages, including
introduction, 5 chapters of content, conclusion and references. The detailed
composition as follow:
Introduction
Chapter 1: Overview on SrTiO
3
materials

Chapter 2: Experimental methods
Chapter 3: The effects of Fe, Co, Ni substitution on structure of SrTi
1-x-
M
x
O
3
materials
Chapter 4: The effects of Fe, Co, Ni substitution on electromagnetic
properties of SrTi
1-x
M
x
O

m3m
(
1
h
O ) and lattice constant of 3.905 Å.
Corner positions of cubic are Sr cations, center of 6 sites is oxygen anion,
center of the cubic is Ti cation. Ion Sr
2+
has coordination number of 12, radius
of r
Sr
+2
= 1.44 Å. Ion Ti
4+
has coordination number of 6, radius of r
Ti
+4
= 0.605
Å. Ion O
2-
has coordination number of 8, radius of r
O
−2
= 1.42 Å. Figure 1.1 is
perovskite at room temperature. At the low temperature, the materials show
phase transition from cubic structure
into tetragonal one of I
4/mcm
(105 K). In
the stoichiometric composition, ratio

3
materials

1.2.1. Electromagnetic properties of SrTiO
3
materials
Dielectric properties of STO used to be
investigated by impedance spectroscopy
measurement. Impedance spectroscopy is
more general than impedance because it
includes phase shift between electric voltage
and current. Normally, vector quantity is
presented by relation
' "
Z( ) Z jZ
ω
= + , in which
Z’ is the real part and Z’’ is the imaginary
part.
On the complex plane, impedance
diagram is presented as figure 1.2 with:

'
Z Z cos( )
θ
= ,
"
Z Z sin( )
θ
= ,

6
.
.

Figure 1.2. components in
complex impedance Zθ

Z
’’

Z
’

Z

0
Y
X
restoration time, the semicircle
can be distortion having center
under the material axis
X. Guo et al investigated
impedance spectroscopy of
single crystal and crystal of
STO. The result for single is 2
semicircles with the
contribution of grain and grain

2-
.
1.2.2. Optical properties of SrTiO
3
materials
For the optical properties of SrTiO
3
materials, it was often focused on
Raman scattering spectroscopy. Theoretically, correlation method can be used
to calculate Raman and infrared active modes in STO crystal. The results show
that in this material, mode 3F
1u
is active infrared and F
2u
is inactive Raman and
infrared. Optical phonons were also investigated in many reports. Oscillation
modes which are typical of 1
st
Raman scattering are: TO
1
mode at around 90
cm
-1
, TO
2
-LO
1
band at around 170 cm
-1
, TO

phase transition from cubic to tetragonal structure at 105-110 K.
For perovskite ABO
3
materials having B site with ions of transition metal
of d group, elements of d and oxygen define properties of materials. Basing on
estimation of energy band, it can be seen that orbital s, p of A have no influence
on width of covalent band ABO
3
.
From diagram of reduced energy of STO (figure 1.10) K. V. Benthem et.
al said that absorbing edge is in accordance with shift from 2p of oxygen and 4p
of Strontium to 3d of Titanium. At near Fermi level, there is hybridization of p
and d. 3d state affects the conduction band and 2p of oxygen in the valence
band. The width of band gap energy is around 3.2 eV, which means that 2p of
oxygen at peaks of valence band to 3d of Ti t
2g
and e
g
in conduction zone.
Bonding of Sr and TiO
6
is strong ionic bonding, while covalent bonding of Ti
and O is the result of 2p (O) and 3d (Ti).
1.3 The effects of substitution on the structure and properties of SrTiO
3

1.3.1. The substitution at site A
1.3.2. The substitution at site B
1.4. Chemical defects of SrTiO
3

(x = 0.0; 0.1;
0.2; 0.3; 0.4 and 0.5), including SrTi
1-x
Fe
x
O
3
, SrTi
1-x
Co
x
O
3
, SrTi
1-x
Ni
x
O
3
.
Systems SrTi
1-x
M
x
O
3
films

was synthesized by PLD with different
contents, including SrTi

2.6. Absorption spectra measurement
Chapter 3
THE EFEECT OF TRANSITION METAL M (Fe, Co, Ni)
SUBSTITUTION ON STRUSTURE OF SrTi
1-x
M
x
O
3
MATERIALS

3.1. The effects of transition metal M on structure of SrTi
1-x
M
x
O
3

synthesized by sol-gel method
3.1.1. Diagram of X-ray diffraction of SrTi
1-x
M
x
O
3
samples
Results of investigation structure of SrTi
1-x
M
x

may be related to the doped of Fe
in Ti
4+
in lattice cells. It was
known that, in octahedral, ionic
radius of Sr
2+
and Ti
4+
are 1.44 Å
and 0.605 Å successively. Ion Fe
with different oxidation state has
different ionic radius. In this
thesis, our result indicates that
lattice constant of SrTi
1-x
Fe
x
O
3

decreases when Fe content
increases. Therefore, it is
estimated that Fe
3+
(LS) or ion
Fe
4+
having smaller ionic radius
substituted for ion Ti

Figure 3.1.
X-ray diffraction diagram of

SrTi
1-x
M
x
O
3
synthesized

by sol-gel method:
(a) SrTi
1-x
Fe
x
O
3
, (b): SrTi
1-x
Co
x
O
3
, (c): SrTi
1-
x
Ni
x
O

0,1
0,2
0,3
0,4
0,5
(b): SrTi
1-x
Co
x
O
3
20 30 40 50 60 70

♥
♥
∗
♠
♠
♠
♦
∗
♦
♥
(c): SrTi
1-x
Ni
x
O
3
0,5

0,3
0,2
0,1
0,0
Figure 3.1b present diagram of X-ray diffraction of SrTi
1-x
Co
x
O
3
samples
by sol-gel method method. The peaks shift at right low Co content (x = 0.1; 0.2)
and expand when Co content rises (x = 0.3; 0.4; 0.5). Especially, at angle of
lager 2θ, diffraction peaks expand and unbalance. Therefore, it is estimated that
when Co content is higher, structural phase can be changed. The results of
lattice constants of SrTi
1-x
Co
x
O
3
indicate the value decreases when Co content
increases. We know that ion Co can exist in many states of oxygen such as:
Co
2+
, Co
3+
, Co
4+
with different ionic radius. Maybe ion Co

ion Ni for Ti
4+
in lattice cells.
According to experimental condition, in substitution ion Ni
2+
for Ti
4+
in
SrTi
1-x
Ni
x
O
3
, if Ni
2+
has radius of 0.69 Å, size of cell and lattice constant will
increase. We know that, like Fe and Co, ion Ni can exist in many oxidation
states. In octahedral crystal, with coordination number of 6, ion Ni
3+
(HS) has
radius of 0.6 Å, Ni
3+
(LS) of 0.56 Å and ion Ni
4+
only exist in HS with radius
of 0.48 Å. It means that in doped with Ni in lattice cells, oxidation states of
Ni
3+
và Ni

O
3
samples, even when Ni content Ni reaches to x ≥ 0.1 grain
size decreases considerably to only 10 nm.
We see that size of crystal grain calculated by formula of Debye-Scherer
is bigger than estimated size from SEM images. The reason is that in
calcinations at high temperature, grains accumulate which lead to increase in
size.
3.1.3. Measurement results of energy dispersive spectra (EDS) of SrTi
1-
x
Fe
x
O
3
samples synthesized by sol-gel method method.
Figure 3.6 presents EDS of SrTi
1-x
Fe
x
O
3
samples. Figure 3.6a shows that
only peaks which correspond with Sr, Ti, O occur. When substituting Fe for a
part of Ti, we see EDS of samples as on figure 3.2 (b-g). Besides, spectrum line
of Fe also occurs at different energy level. When Fe content is of x = 0.1; 0.2,
spectrum lines which are typical of Fe occur at about 0.7 and 6.2 keV. When Fe
content is of x = 0.3; 0.4; 0.5, there is also another spectrum line at around 7.1
keV. In substitution Fe, intensity of spectrum peaks of Ti tend to decrease
gradually and spectrum peaks of Fe tend to increase. This result is suitable to

3
samples synthesized by sol-gel method,
structure of this samples are cubic of P
m3m
. On the diagram, diffraction peaks of
pure STO film have high intensity at 2θ of about 22, 32, 40, 50
o
which
correspond with Muller index (100), (110), (111), (210). When substitute
element and its content is different, intensity as well as diffraction peaks also
change. Figure 3.7 show the XRD of Fe doped STO samples. Diagram presents
x = 0.0

0.1 Fe

0.2 Fe

0.3 Fe

0.4 Fe

0.5 Fe

Figure 3.3. SEM images of SrTi
1-x
Fe
x
O
3
samples synthesized by sol-gel method

4+
in SrTi
1-x
Co
x
O
3
films, ion Ni
4+
or Ni
3+

(LS) replaced ion Ti
4+
in SrTi
1-x
Ni
x
O
3
films.
Figure 3.6. Energy dispersive spectra of SrTi
1-x
Fe
x
O
3
samples

(x = 0.0 ÷ 0.5) synthesized by sol-gel method.

4
6
8
10
Fe
Sr
Sr
Ti
Ti
Fe

Fe

Ti

O
(e): SrTi
0.6
Fe
0.4
O
3

0

2
4
6
8
10

Sr
Ti
(a): SrTiO
3

0 2 4 6 8 10
O
Fe
Sr
Sr
Ti
Ti

Ti

Fe

(b): SrTi
0.9
Fe
0.1
O
3

O

Fe

Sr
Sr

PLD method.
From AFM of SrTi
1-
x
Fe
x
O
3
films (x = 0 ÷ 0.3), we
can observe surface
morphology and estimate grain
size. Results indicate that
lattice models accumulating on
layer Si (100) have averagely
small width of 0.10 µm.
3.3. Comparison and
discussion structure of SrTi
1-
x
M
x
O
3
samples.
After investigating
structure of two SrTi
1-x
M
x
O


films, only some peaks occur.
The reason for this
phenomenon is that when we
irradiate X-ray on SrTi
1-x
M
x
O
3

samples, X-ray will diffract to
all directions, and on SrTi
1-
x
M
x
O
3
films, X-ray diffract to
1 priority direction- direction of layer.
20 30 40 50 60
(c): Films SrTi
1-x
Ni
x
O
3
x
O
3

(111)
(210)
(110)
(100)
∗
0,2
0,1
0,0
2θ (degree)
Intensity (arb. units)
Figure 3.7. Diagram of X-ray diffraction
of SrTi
1-x
M
x
O
3
films synthesized by PLD:
(a) SrTi
1-x
M
x
O
3
films, (b) SrTi
1-x

3
films, although diffraction peaks are a few, we still gain
pure samples in substitute limitation.
Chapter 4
THE EFFECTS OF TRANSITION METAL IONS M (Fe, Co, Ni) ON
ELECTROMAGNETICS PROPERTIES OF SrTi
1-x
M
x
O
3
MATERIALS

4.1. The effects of transition metal ions M on electronic properties on SrTi
1-
x
M
x
O
3
synthesized by sol-gel method
4.1.1. The effects of Fe doped on electronic properties of SrTi
1-x
Fe
x
O
3

synthesized by sol-gel method
Figure 4.1 presents impedance spectroscopy of SrTi

6
9
(g): SrTi
0.5
Fe
0.5
O
3
Data
Fit
Z' (k
Ω
)
- Z'' (k
Ω
)
50 100 150 200
0
15
30
45
Z' (k
Ω
)
Data
Fit
(d): SrTi
0.7
Fe
0.3

Data
Fit
- Z'' (M
Ω
)
Z' (
ΜΩ
)
(b): SrTi
0.9
Fe
0.1
O
3
0 2 4 6 8 10
0
1
2
3
Data
Fit
- Z'' (M
Ω
)
Z' (M
Ω
)
(a): Sample x = 0.0
Figure 4.1. Impedance spectroscopy of SrTi
1-x

Co
x
O
3
materials
synthesized by sol-gel method.
In experimental condition and limitation of frequency range of 10 Hz –
5.3 MHz, for Co doped STO, we only define impedance value of pure STO and
Co doped samples with content of x = 0.1; 0.3. From experimental data, we can
not draw semicircles with Co content of x = 0.2; 0.4; 0.5. Therefore, resistance
and capacitor value of grain local, boundary grain, electrodes also have been
defined yet. According to impedance diagram of samples SrTi
1-x
Co
x
O
3
, for Co
substituted samples, impedance spectroscopy is a semicircle without going
through origin O. It means that impedance value is contributed mainly by grain
boundary
4.1.3. The effects of ion Ni on electric properties of SrTi
1-x
Ni
x
O
3
materials
synthesized by sol-gel method
The diagram of Ni doped SrTi

experimental data and semicircle, we can define maximum frequency,
resistance value of grain local and boundary, capacitance value.
4.2.2. The effects of ion Co on electric properties of materials SrTi
1-x
Co
x
O
3

synthesized by PLD method.
Results impedance spectroscopy of SrTi
1-x
Co
x
O
3
(with x = 0.0 ÷ 0.4)
synthesized by PLD show that, impedance spectroscopy of SrTi
1-x
Co
x
O
3
is
semicircles not going through origin O, so grain boundary contribute mainly to
the impedance value.
4.2.3. The effects of ion Ni on electric properties of SrTi
1-x
Ni
x

3
samples

synthesized by sol-gel and PLD method
The basic difference of two samples is that impedance of SrTi
1-x
M
x
O
3
powder is contributed by grain, grain boundary and electrodes, while
impedance of SrTi
1-x
M
x
O
3
samples

are mostly contributed by grain boundary.

Resistance of SrTi
1-x
Fe
x
O
3
, SrTi
1-x
Co

O
3
) resistance does not depend on the
concentration of doping ions.

4.4. Effect of doping transition metals M on magnetic responses of SrTi
1-
x
M
x
O
3
samples synthesized by sol-gel and PLD
4 8 12
0
2
4
Data
Fit
Z' (k
Ω
)
- Z'' (k
Ω
)
(b): 0.1 Fe
0 5 10 15 20
0
4
8

by PLD

4.4.1. The effects of transition metal ions M on magnetic properties on
SrTi
1-x
M
x
O
3
synthesized by sol-gel method
Figure 4.9 show that pure STO
and 10% doped sample (x = 0.1)
present both diamagnetic and
ferromagnetic. When Co and Fe
content increases, magnetic
properties increase, but have not
been saturated. This means that
electromagnetic field H = 13500 Oe
is not big enough to define all
domains. For SrTi
1-x
Ni
x
O
3
, the
saturated value increases in
accordance with Ni content.
As we know, STO is
diamagnetic, but for sample with x =

n+
that cause magnetic responses.
Besides, accumulation of oxides of
Fe in SrTi
1-x
Fe
x
O
3
, existence of Ti
(Ti
3
O
5
, TiO
2
) and Ni in SrTi
1-x
Ni
x
O
3

also cause magnetic responses. For SrTi
1-x
Co
x
O
3
, the reason for magnetic

x
O
3
samples,
(b) SrTi
1-x
Co
x
O
3
samples, (c) SrTi
1-x-
Ni
x
O
3
samples ( x = 0.0 ÷ 0.5).
-10000 -5000 0 5000 10000
-0.08
-0.04
0.00
0.04
0.08
(b): SrTi
1-x
Co
x
O
3
0,0


0,0
0,1
0,2
0,3
0,4
0,5
(a): SrTi
1-x
Fe
x
O
3

M (emu/g)
H (Oe)
and diamagnetic. Magnetism curve in
figure 4.11 presents: (1) general
magnetism curve, (2) diamagnetic
line, (3) ferroelectric line. Similarly,
for SrTi
1-x
Co
x
O
3
samples

(x = 0.0 ÷
0.4) and SrTi

O
3
. When the content
reaches to 20 %, samples Sol-gel have
ferromagnetism, and samples by PLD
show both ferromagnetism and
diamagnetism.
As we know, pure STO is
dielectric, so it does not have
magnetism at normal condition. However, by doping transitional metal for Ti,
this material have complicated responses. Many results focused on researching
magnetic responses of STO doped Fe, Co. A. Sendil Kumar et. al investigated
magnetic responses of SrTi
1-x
Fe
x
O
3-δ
(x = 0,2; 0,3; 0,5; 0,7; 0,9). The diagram
M (T) indicates that when concentration of Fe was small (20%), the materials
have antiferromagnetic responses and temperature Neel T
N
increased with Fe
concentration.
S. Srinath et. al synthesized SrFe
x
Ti
1-x
O
3-δ

(c): Film x = 0.2 Fe
(3)
(2)
(1)
-10000 -5000 0 5000 10000
-5.0x10
-4
0.0
5.0x10
-4
(b): Film x= 0.1 Fe
(3)
(2)
(1)
-10000 -5000 0 5000 10000
-6.0x10
-4
-3.0x10
-4
0.0
3.0x10
-4
6.0x10
-4
(3)
(2)
(a): Film x = 0.0
(1)
M (emu/g)
H (Oe)


5.1. The effects of M doped on Raman
scattering spectroscopy of SrTi
1-x
M
x
O
3

synthesized by sol-gel method
Raman scattering spectroscopy of
samples SrTi
1-x
M
x
O
3
(M = Fe, Co, Ni) at
room temperature in figure 5.1. In pure
STO sample, optical phonons are
activate, strong peak is at 170 cm
-1
of
band TO
2
-LO
1
, weak peak at 234 cm
-1


x
M
x
O
3
have strong peak at approximately
700 cm
-1
. Change in oscillation and
occurrence of new peaks can be related to
distortion of octahedral TiO
6
. In
substitution M for Ti, radius difference
causes bonding energy and length among
ions in cells. Therefore, oscillation lines
on Raman scattering spectroscopy
change. This result is suitable to that
250 500 750
(c): SrTi
1-x
Ni
x
O
3

0.5
0.4
0.3
0.2

3
-LO
2
TO
4
LO
4
, A
2g
(b): SrTi
1-x
Co
x
O
3
200 400 600 800 1000
B
2g
0.5
TO
2
,
LO
1
TO
3
-LO
2
TO
4

Fe
x
O
3

samples, (b) SrTi
1-x
Co
x
O
3
samples,
(c)
SrTi
1
-
x
Ni
x
O
3

samples
.

gained by analysis of X-ray diffraction when lattice constant changes of SrTi
1-
x
M
x

-1
occur
because of 2
nd
Raman scattering. Raman scattering spectroscopy in Fe, Co, Ni
doped samples is different. In addition to typical spectrum of oscillation mode
TO
4
, there are other modes which are typical of 2
nd
oscillation at around 700
cm
-1
.
Temperature of phase transition of SrTi
1-x
Fe
x
O
3
samples is 110-160 K, of
SrTi
1-x
Co
x
O
3
samples at 110-130 K and of SrTi
1-x
Ni

2g
in accordance with 177, 270, 480, 544,
792 cm
-1
. When Co content increases, there are 2 peaks at 430 and 750 cm
-1
of
2 bands 300-500 cm
-1
and 650-850 cm
-1
. Besides that, peak intensity of 2
nd

scattering B
g
(230 cm
-1
) and oscillation modes 578 cm
-1
increases considerably.
It is clear that when Co, Ni content rises, on SrTi
1-x
M
x
O
3
films typical
oscillation modes of 2
nd

4
,
LO
4
-A
2g
. besides, there are 2 wide peaks in range of 200-400, 600-800 cm
-1
and
mode B
2g
at 230 cm
-1
which are assigned to 2
nd
scattering modes. This result is
relatively suitable to previous reports.
For SrTi
1-x
M
x
O
3
samples at room temperature, when substitute ion
content increases, there is only one typical mode of 2
nd
Raman in range of 700
cm
-1
.

3
films, Raman scattering spectroscopy have wide peaks in 300-500 cm
-1

and intensity of oscillation mode B
2g
increases in spite of low Co content (x =
0.1), then decrease when Co content increases. However, for SrTi
1-x
Ni
x
O
3
films,
when Ni content increases, the shapes of scattering spectrum at x = 0.1 and 0.2
are the same, typical mode of 2
nd
scattering occur in 600-800 cm
-1
. If Ni content
reaches to x = 0.3, Raman scattering spectroscopy will have other characters
from 2 these samples, with oscillation mode at 300 and 613 cm
-1
.
It can be seen that different substitute contents cause different phase
transition temperatures which are higher than that of pure STO sample.
Moreover, with different method of synthesized samples, Raman scattering
spectroscopy of SrTi
1-x
M

on Fe content of band gap energy. When
substituting a part of Fe
3+
for Ti
4+
,
samples can absorb in visible zone and a
part of infrared zone.
The reason for reduction of
forbidden band width when Fe
3+
content
increases is dopant in STO. As we know,
STO is dielectric materials with high
band gap energy lager. When replacing
ion Fe, 3d of Fe is over 2p of O on covalent band, which causes the width of
band gap energy decreases. This result was also affirmed by experimental and
X- ray photoelectron spectrum X (XPS).
Figure 5.9. Absorption spectra
of SrTi
1-x
Fe
x
O
3
(x = 0.0 ÷ 0.5).
300 450 600 750
Absorption (arb. units)
Wawelenght (nm)
0.0

Fe, Co, Ni in STO has been examined by density functional theory (DFT).
5.6. Electronic structure and Density of State (DOS) of Fe, Co doped SrTi
1-
x
M
x
O
3

In this thesis, we use LDA (Local Density Approximation) to computer
region structure, DOS of Fe, Co doped STO with CASTEP program
(Cambridge Serial Total Energy Package). Crystal structure of STO was taken
from library of Materials Studio.
Figure 5.13 presents energy region structure and DOS of pure STO,
which are similar with the previous reports. It can be seen that peak of covalent
band and base of band locate at G and Z spot on Brillouin zone ( Figure 5.13a)
with value of 1.68 eV, while experimental value is 3.2 eV because of LDA
method, which ignore interaction among electronic gas.
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
ZQF G



O 2p
DOS

Energy (eV)
(b)
Figure 5.13. Diagram of
structure of energy region (a)
and density of state (b) of pure
SrTiO
3
.
In diagram of partly density of states PDOS (Figure 5.13b), covalent
region was contributed by 2p of O. In the conducting region, 3d state was
predominant. This means that when replacing or doping electron for STO
material, impure energy levels were formed, or Fermi level sifted to conducting
region, causing width of band gap energy decrease.
Structure of energy region and DOS of 12,5 and 25% Fe doped STO are
presented on figure 5.14. From the structural diagram of energy region (figure
5.14a), impure energy bands over Fermi were formed, causing the width of
band gap energy decrease to 0,86 eV. Diagram density of state (DOS) in figure
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Z
Q

Fe 3d
Ti 3d
Sr 5s

O 2p
DOS
(b)
Energy (eV)
Figure 5.14. Fe doped SrTi
1-x-
Fe
x
O
3
with x = 0.125. (a)
structure of energy region, (b)
density of state.

Energy (eV)
-5 -4 -3 -2 -1 0 1 2 3 4 5
0
50
100
150
0
40
80
0
20
40

ZQF G
G
(a)
Energy (eV)
Figure 5.15. Fe doped SrTi
1-x-
Fe
x
O
3
with x = 0.25. (a)
structure of energy region, (b)
density of state.

5.14b indicates that at the Fermi energy level and proximity levels, electronic
concentration of 3d state was predominant.
From the diagram structural of energy region 25% doped Fe SrTi
1-x
Fe
x
O
3

materials ( figure 5.14a), it is clear that, the impurity cover on valence peak has
become impure energy region. Therefore, electrons moved from the peak of
impure energy region to base of conducting band, which caused decrease in the
width of band gap energy to around 0.75 eV. In the density of state, we

1-x
Cu
x
O
3
. Thence, electrons
moved from impure energy band to peak of conducting region, leading decrease
in the width of the band gap energy. Diagram density of states indicates that, at
the proximity of Fermi, electronic concentration of Oxygen 2p and Co 3d were
predominant.
CONCLUSION

1. SrTi
1-x
M
x
O
3
systems (M = Fe, Co, Ni; x = 0.0 ÷ 0.5) have been
prepared by Sol-gel and PLD method. The samples received by this method
give good quality, satifying requirements of the investigation. By sol-gel
method, temperature in phase formation decreased considerably from 1200 to
900
o
C. Especially, the preparation of SrTi
1-x
M
x
O
3

M
x
O
3
samples prepared by Sol-gel method, when concentration of
doped ions was low, (x = 0.1), samples shown both paramagnetic and
ferromagnetism. When the concentration was higher (x ≥ 0.2), samples shown
only ferromagnetism. In the measurement range of electromagnetic field (from
-13500 to 13500 Oe), only magnetization of SrTi
1-x
Ni
x
O
3
samples reached
saturation value.
For SrTi
1-x
M
x
O
3
samples prepared by PLD method, when the
concentration of doped ions increased, all samples had both paramagnetic and
ferromagnetism.
5. At the room temperature, Raman scattering spectroscopy of the pure
SrTiO
3
samples prepared by Sol-gel and PLD method also shown typical
oscillation modes of first order Raman scattering spectrum and two bands of the

1-x
M
x
O
3

prepared by Sol-gel at the low temperature, it was indirectly inferred that
temperature of phase transition was around 110-160 K.
Measurement result of absorption spectra on SrTi
1-x
M
x
O
3
materials
synthesized by sol-gel indicated that, absorption edge shifted to high wave-
length (low energy), there was complete light absorption in visible area and
infrared area. It can be predicted that a part of Fe, Co, Ni ions has contributed
to the structure and become acceptor contaminant, increasing conductivity of
the prepared materials. This predication has been supported by structural energy
region and density of states.
Diagram structural of energy region and density of states defined that
when Fe, Co were substituted in SrTi
1-x
M
x
O
3
,