International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2014): 5.611
Calculation Parameters of Proton Ions in Indium Tin
Oxide and Polyethylene Terephthalate
M. H. Eisa1, 2
1
Department of Physics, College of Science, Sudan University of Science and Technology, Khartoum 11113, Sudan
2
Physics Department, College of Science, Al Imam Mohammad Ibn Saud Islamic University, Riyadh, 11432, Saudi Arabia
Abstract: It is well known that, when a material bombarded with energetic ions, many processes are initiated and this gives rise to a
variety of physical and chemical phenomena. Stopping power and range of compounds was calculated by using the Stopping and Range
of Ions in Matter (SRIM) code. Calculations were done for Indium Tin Oxide (ITO) and Polyethylene terephthalate (PET) targets by
using the SRIM. Results are presented and compared with the latest published data. The details of calculations are given and discussed.
Keywords: Energy loss; Stopping power; ITO; PET; SRIM
1. Introduction
The physics of the interactions of ions with matter is
currently a subject of great interest due to its relevance both
in basic research and in numerous applications. The study of
stopping power and range theory has attracted physicists for
the several decades. For over a century, the stopping of
energetic ions in matter has been a subject of great
experimental and theoretical interests. Many measurements
of these energy loss values have been made, for many
incident beams and targets. Current theoretical models
predict stopping powers that are not always in good
agreement with each other [1]. The accuracy with which the
stopping powers are known is currently rather poor. The
main reason for this poor accuracy is that the experimental
determination of stopping powers by traditional methods is
difficult, involving preparation of pure thin targets and
accurate measurements of their thicknesses [2]. Due to
experimental difficulties in preparing and handling
compound targets for energy-loss measurements, heavy-ion
stopping data in compounds are very limited. The
knowledge of stopping power of ions in various films is
important in several fields of applications [1]. However,
stopping powers and ranges have played a crucial role in
many aspects of heavy-ion physics [2]. Stopping power can
be considered in two parts: first is the interaction of incident
particle with target electrons (called electronic stopping
power), and second is the interaction with target nuclei
(called nuclear stopping power). The first (classical)
calculation of the energy loss of energetic particles was
made by Bohr [3], while the first quantum mechanical
treatment was done by Bethe [4]. This latter theory of
stopping power is particularly accurate when the projectile’s
velocity is sufficiently high. Another important quantity is
the range of the charged particle in matter. The range is
defined as the mean path length of the particle in the target
matter before coming to rest.
Researchers have attempted to deposit transparent
conducting ITO thin films on several polymeric substrates
[5]. ITO thin films are widely used in solar cells and other
applications. Currently PET substrate is the most popular
investigated one because of its processing maturity, low cost,
and high transmission [6]. In this study, SRIM 2013 code
Paper ID: NOV161855
was applied to simulate the stopping power and the range of
protons in ITO on a plastic substrate, PET. Detailed
descriptions and discussions of the physical background of
SRIM 2013 code can be found in literature [7].
2. Materials and Methods
2.1. The ITO samples preparation
The structure of ITO target having an In2O3: SnO2
composition of 90: 10wt. %. The chemical composition (for
an indium oxide/ tin dioxide ratio of 90:10) is given as
Indium (74.52%), Oxide (17.60%) and Oxide (7.88%). ITO
is essentially formed by subsititutional doping of In2O3 with
Sn which replaces the In3+ atoms from the cubic bixbyte
structure of indium oxide [8]. ITO films have a lattice
parameter close to that of In2O3 and lie in the range 10.12 to
10.31Å [9].
2.2.
The PET samples preparation
PET has a molecular formula (C10H8O4). PET finds
application in a wide array of fields.
2.3. Methods of Calculations
The theoretical calculations of the stopping power and range
of several energetic proton beams of up to 10 MeV in targets
were carried out using the SRIM 2013 version codes. In
every investigated the proton energy, there were nearly
10,000 protons simulated in the calculations. The proton
distributions in targets can be examined from the particle’s
stopping power/energy loss and range, which can be
calculated using SRIM code [10]. In the SRIM codes,
stopping power is defined as the energy required to slowing
down the incident particle during its interaction with matter
over a certain distance, and is mathematically expressed as
[11]:
S E =−
dE
dx
=
4πk 2 z 2 e 4 n
mc 2 β2
2
[ln
2mc 2 β2
I (1−β2 )
− β2 ] (1)
2
Where, k is 8.99 ×109 N.m .C , z is atomic number, e is
charge of electron, n is number of electron per unit volume
of the target, m is mass of electron at rest, c is speed of light
in vacuum, β is a ratio of the speed of the incident particle to
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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2014): 5.611
the speed of light, I is an average excitation energy of the
target. However, after losing energy due to electronic and
nuclear interactions, the incident ion will eventually stop at a
certain distance from the target surface and leave some
vacancies in the target. The distance over which the ion
totally stops is called the projected range R (E), which
satisfies [11]
E
powers
of
0.1MeV
0.2882MeV/(mg/cm2).
protons
in
ITO
were
dE
dE (2)
R= 00 −
dx
This quantity is known as the reciprocal stopping power
range. Where, E0 is the incident ion energy at the target
surface, x is the distance measured along the ion path, dE/dx
is the energy loss (which has both nuclear and electronic
energy loss part) of the ion with energy E. Because of ITO
and PET targets importance, we have used SRIM version
2013 program for stopping power and range calculations.
The description of ions and targets are given in Tables 1-4.
Table 1: Ion description
Element
Atomic Number Mass (amu) Ion Energy Range (keV)
Lowest
Highest
Hydrogen
1
1.008
10
10000
Table 2: ITO Target description
Element
Atomic Number Weight (amu)
Oxygen, O
8
15.999
Indium, In
49
114.82
Tin, Sn
50
118.71
Oxygen, O
8
15.999
Stoich
3
2
1
3
Atom%
33.33
22.22
11.11
33.33
Figure 1: The stopping power of ITO for protons, plotted
versus ion energies
Electronic stopping powers of 0.01–10MeV protons in PET
target was calculated using SRIM to be (0.4108–
0.04311MeV/gm cm2), while nuclear stopping power was
(0.006983–0.00002248MeV/gm cm2). Figure 2 depicts the
variation of electronic and nuclear stopping power of 0.01–
10MeV protons with ion energy.
Table 3: PET Target description
Element
H
C
O
Atomic Number Weight (amu) Stoich
1
1.008
8
6
12.011
10
8
15.999
4
Atom%
36.36
45.45
18.18
Table 4: ITO/PET Target description
Element Atomic Number Weight (amu) Stoich
O
In
Sn
O
H
C
O
8
49
50
8
1
6
8
15.999
114.82
118.71
15.999
1.008
12.011
15.999
3
2
1
3
8
10
4
Atom%
9.68
6.45
3.23
9.68
25.81
32.26
12.90
3. Results and Discussion
3.1. Stopping Power of Energetic Proton Beams in ITO,
PET and ITO/PET Targets
In the present study, systematic calculations of the stopping
powers and range for 0.01–10 MeV protons in ITO, PET,
and ITO/PET targets are carried out using Ziegler's program
SRIM 2013. Electronic stopping powers of 0.01–10MeV
protons in ITO target was calculated using SRIM to be
(0.126–0.02613 MeV/gm cm2), while nuclear stopping
power was (0.002284–0.00001270 MeV/gm cm2). Figure 1
depicts the variation of electronic and nuclear stopping
power of 0.01–10MeV protons with ion energy. From this
figure, it was clear that the electronic stopping power
mechanism dominated the nuclear stopping power. The low
electronic stopping powers of 10MeV protons in ITO were
0.02613 MeV/ (mg/cm2). While the high electronic stopping
Paper ID: NOV161855
Figure 2: The stopping power of PET for protons, plotted
versus ion energies
The low electronic stopping powers of 10MeV protons in
PET were 0.04311MeV/ (mg/cm2) .While the high
electronic stopping powers of 0.08MeV protons in PET were
0.7675MeV/(mg/cm2). The low electronic stopping powers
of
10MeV
protons
in
PET
were
0.03125MeV/(mg/cm2) .While the high electronic stopping
powers
of
0.09MeV
protons
in
PET
were
0.4225MeV/(mg/cm2). Nuclear stopping increases when the
energy of the ion increases. In the figures 1, 2 and 3,
electronic stopping at low and high energy is larger than
nuclear stopping. For very light ions slowing down in heavy
materials, the nuclear stopping is weaker than the electronic
at all energies. At even higher energies, one has to consider,
in addition, irradiative stopping power which is due to the
emission of bremsstrahlung in the electric fields of the
nuclei of the material traversed. Close to the surface, both
nuclear and electronic stopping may lead to sputtering. We
find the energy loss depends on the ordering of the target
ITO and PET and is significantly different for the two cases.
Electronic stopping powers of 0.01–10MeV protons in
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International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2014): 5.611
ITO/PET target was calculated using SRIM to be (0.2084–
0.03125 MeV/gm cm2), while nuclear stopping power was
(0.003702–0.00001569 MeV/gm cm2). Figure 3 depicts the
variation of electronic and nuclear stopping power of 0.01–
10MeV protons with ion energy.
Figure 5: The range of PET for protons, plotted versus ion
energies
Figure 3: The stopping power of ITO/PET for protons,
plotted versus ion energies
3.2. Projected, longitudinal and lateral range of proton
in ITO, PET and ITO/PET target
The projected range, the longitudinal range and the lateral
range values of 0.01–10MeV protons in ITO was calculated
using SRIM to be (0.0000001567–0.00066168m),
(0.0000001008–0.00003472m)
and
(0.0000000845–
0.00005046m), respectively. Figure 4 depicts the variation
of projected range, longitudinal range and lateral range of
0.01–10MeV protons with ion energy. The Figure 4 shows
how the range of ITO for protons increases until it reaches
the maximum.
The projected range, the longitudinal range and the lateral
range values of 0.01–10MeV protons in ITO/PET was
calculated using SRIM to be (0.0000002976–0.00132m),
(0.0000001392–0.0006444m)
and
(0.0000001244–
0.00007927m), respectively. Figure 6 depicts the variation
of projected range, longitudinal range and lateral range of
0.01–10MeV protons with ion energy. The Figure 6 shows
how the range of ITO/PET for protons increases until it
reaches the maximum.
Figure 6: The range of ITO/PET for protons, plotted versus
ion energies
Figure 4: The range of ITO for protons, plotted versus ion
energies
The projected range, the longitudinal range and the lateral
range values of 0.01–10MeV protons in PET was calculated
using SRIM to be (0.0000001974–0.00093064m),
(0.0000000528–0.00004169m)
and
(0.0000000547–
0.00002602m), respectively. Figure 5 depicts the variation
of projected range, longitudinal range and lateral range of
0.01–10MeV protons with ion energy. The Figure 5 shows
how the range of PET for protons increases until it reaches
the maximum.
Paper ID: NOV161855
The projected range, the longitudinal range and the lateral
range of ITO, PET and ITO/PET increased when energy
increased. The behavior of the range and ion distribution is
relatively similar for ITO and PET targets. To determine the
accuracy of the Range results, we have compared our results
with various results in the literature. The longitudinal and
lateral distributions of a 0.01–10MeV protons beam
bombarded into a target can be seen in Figures 4-6, in which
the incident proton hit the target and stop after passing
through a distance in targets. The incident proton is scattered
off the target atoms at an angle of less than 90ᵒ, but there are
no backscattered ions observed in the simulation. The
behavior of the proton beam distributions in the energy
range between 0.01 MeV and 10 MeV is relatively similar
which can be inferred from the shape of their energy
loss/stopping power plots (Figures 1, 2 and 3). In general,
for any proton energy, the stopping power increases with
increasing distance of travel until it peaks at a certain value
(called Bragg peak) and then drops dramatically following
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ISSN (Online): 2319-7064
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the loss of the proton energy. In contrast to the general trend
of the energy loss, in which it decreases with increasing
proton energy, the range increases with increasing proton
energy as shown in the inset of Fig. 4, 5 and 6.
4. Conclusions
In the present study stopping power and range of protons in
ITO, PET and ITO/PET are calculated by SRIM code. The
calculations showed that the lateral and longitudinal
straggling are dependent on atomic number of ion particle
and the target density. Knowledge about stopping power and
range of proton in target is essential to better understand the
behaviour of the particle’s distribution in the target. As the
problems in measuring stopping powers have traditionally
been associated with difficulties in the experimental
methods, the alternative we present could become extremely
useful. The present results of the proton stopping power and
range for these materials in the energy range from 0.01 to 10
MeV might be useful for studies of various ion effects in
these materials.
5. Acknowledgement
The help of many users of SRIM and friends in various
phases of this work is gratefully acknowledged.
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