SRIM Simulation of Parameters Affecting Sputtering Yield and Chemical Structure Using Kr, Cu and Pb Ions Bombardment

Transcription

1 The Egyptian Arab Journal of Nuclear Sciences and Applications Society of Nuclear Vol 50, 4, ( ) 2017 Sciences and Applications ISSN Web site: esnsa-eg.com (ESNSA) SRIM Simulation of Parameters Affecting Sputtering Yield and hemical Structure Using Kr, u and Pb Ions Bombardment M.M. Shehata a,b*, S.I. Radwan c and A.M. Abdel Reheem c (a) Radiation hemistry Department, National enter for Radiation Research and Technology, Atomic Energy Authority, Egypt (b) entral Laboratory for Elemental and Isotopic Analysis, Nuclear Research enter, Atomic Energy Authority, Egypt (c) Accelerators & Ion Sources Department, Nuclear Research enter, Atomic Energy Authority, airo, Egypt Received: 23/1/2017 Accepted: 20/8/2017 ABSTRAT 1 Sputtering yields of various extracted kyrpton, copper and lead ions with energies from 5 50 KeV on Polycarbonate/ polybutylene terephthalate film were investigated. SRIM computer program was used to determine the sputtering yield and supsequntly the change in chemical structure. The relation between the ion beam energy and sputtering yield of hydrogen, carbon and oxygen was studied. The effect of ion beam incidence angle on Polycarbonate/ polybutylene terephthalate film was investigated. The total sputtering yield at an energy of 50 KeV was 1.986, and for copper, krypton and lead ions respectively. It is found that the sputtering yield for hydrogen is the highest. The sputtering yield increases by decreasing the atomic number of the element in the target. Key Words: TRIM Program / Polycarbonate/ Polybutylene Terephthalate Film/ Sputtering / Sputtering Yield INTRDUTIN Polymers have much importance in widespread applications in different fields of science and technology, due to their inherent versatile properties like light weight, easy process ability, high packing density, high optical clarity, high mechanical strength, resistance to collision, etc (1-4). The most important feature of their utilization in many electrical and electronic devices is only limited to the electrical insulation because of the high electrical resistance offered by their surface (5-9). Many techniques like doping, pulsed laser deposition, plasma deposition, ion implantation, surface etching by chemicals and others are used to improve the surface properties of polymers (8-16). Ion beam irradiation of polymers result in the modification of their chemical and physical properties was studied. The interaction of different charged ions with different energies on an organic matrix occurs in the electronic energy loss regime, inelastic collision S e, even when the nuclear energy losses, elastic collision S n, are not negligible at all (17-18). In electronic loss regime, phenomena of chain scissions and cross-linking and/or bond configuration with the subsequent nucleation and growth of carbon based structures are induced. This is a final result of a process starting with the release of gaseous compounds as 2, 2, 4, etc. (19). Bayfol R polymer is a blend of translucent polycarbonate/ polybutylene terephthalate based film that offers superior fatigue resistance, abrasion resistance along with added chemical resistance. It displays considerably better formability, improved dynamic load-bearing capacity and better resistance to the influence of chemicals than a pure 1 orresponding author m_shehata2100@yahoo.com

2 polycarbonate film. Its films are extremely versatile films used in a broad range of applications such as instrument panels, trade show displays, membrane switches, control panels and decals. They offer excellent light-diffusing characteristics, improved UV and chemical resistance, and other proven properties (20). SRIM is a software package concerning the Stopping and Range of Ions in Matter used to calculate various physical quantities related to ion implantation, energy deposition and other effects of interaction of ions with matter (21). It is a well-established and highly recognized code in the community of ion-beam users. owever, the standard SRIM version uses a simplified beam model for Monte arlo simulations. It is able to calculate backscattered and sputtered particle distribution functions resulting from positive atomic- ion bombardment of any amorphous surface. So that, it can be used to simulate nuclear reactions processes, e.g. neutron induced alpha-particles created throughout reactor materials. SRIM is formerly TRIM which calculates both the final 3D distribution of the ions and also all kinetic phenomena associated with the ion's energy loss as target damage, sputtering, ionization, and phonon production. Ion bombardment of solids with energetic particles causes the erosion of target material s surfaces. The erosion rate is characterized by the sputtering yield, Y, defined as the average number of atoms leaving the surface of a solid per incident particle. The theory of ion sputtering based upon the microscopic considerations of the processes taking place in the bulk of the bombarded material, was developed by Sigmund (22-24). ne of the practically important results obtained by Sigmund is the deposited energy distribution function, which was found to have the Gaussian form: Є z2 E(r, z) = exp [ X2+Y2 ] (1) (2π)3/2σμ2 2σ2 2μ2 where, Є is the kinetic energy of an incident ion, σ and μ are the widths of the deposited energy distribution along the z- (chosen parallel to the incident ion beam direction) and x (y)-axis, respectively. The parameters σ and μ are the material dependent and vary with the physical properties of the target material and the incident ion energy. Deviations of the deposited energy distribution from the Gaussian form (see eq. 1) occur mainly when M 1 M 2, where M 1 and M 2 are the masses of the projectile and the target material atom. In general, computation of the sputter yield, using equation 1 requires the knowledge of the mean path of an incoming ion, traveling inside the bulk of a target material (often referred to as penetration depth). It was shown that the penetration depth can be expressed in terms of the parameters characterizing the target material and the incoming ion energy as follows: a(є) = 1 m 2m γm-1 Є 2m (2) n m where, n is the target atom density, γ is a constant of the order of unity, m is a constant dependent on the parameters of the inter-atomic interaction potential and m=m (Є) is a factor, which varies slowly from m = 1, at high energies, to m = 0, at very low energies [15]. It must be emphasized that, in the region of intermediate energies, Є, m = 1/2 and the penetration depth behavior with the incoming ion energy can be approximated well by the linear dependence, a (Є) ~ Є. Generally, the deposited energy distribution is defined by the energy deposition depth and not the penetration depth, a. n the other hand, these quantities are of the same order of magnitude and, therefore, in the following, we assume that the estimates for a can be used to approximate the energy deposition depth. In the framework of the Sigmund s theory of ion sputtering, the local yield from a target material surface element (ds) can be computed using: Y (r) ds = Λ E (r) ds (3) Where Y(r)ds is the total number of the target atoms leaving the surface element ds, located at a distance r on the target material s surface from the point of impact of the projectile, and E (r) the energy deposited by the incoming ions at a point r, taken per unit volume.

3 In the present study, computer simulation was performed by using the Monte arlo program TRIM to confirm and discuss the effect of target density and bonding energy in sputtering yield and chemical structure changes of Polycarbonate/ polybutylene terephthalate film. This program is based on the binary collision approximation and it uses a randomized target structure, that is, amorphous. Therefore, the program TRIM is suitable to simulate the experiments performed in this work. RESULTS AND DISUSSIN 1- Effect of Various Ion Beams Figure 1 (a, b and c) shows the ion beam energy (KeV) versus sputtering yield (Atom/Ion) of krypton, copper and lead ions at angle equal to zero (perpendicular to the target) on Polycarbonate/ polybutylene terephthalate film. This polymer consists of, and and after irradiation the chemical composition was changed this may be attributed to the formation of free radicals that leads to cross linking or degradation of the polymer. The simulation studied the sputtering yield for carbon, hydrogen and oxygen using Krypton, copper and lead ions at various energies from 5 to 50 KeV. It was found that the sputtering yield for hydrogen is the highest. This implies that, as the sputtered atomic number of element from Polycarbonate/ polybutylene terephthalate film is decreased, the sputtering yield is increased. Also, the sputtering yield increases by increasing the ion beam energy from 5 to 50 KeV. The sputtering yield increased from copper, krypton and lead. Lead give the high sputtering yield as appear in Table (a) (b) (c) Fig. (1): Ion beam energy (KeV) versus sputtering yield (Atom/Ion) of (a) krypton, (b) copper and (c) lead ions at angle zero on Polycarbonate/ polybutylene terephthalate film.

4 Table (1): Sputtering yields of oxygen, carbon and hydrogen for sputtering Polycarbonate/ polybutylene terephthalate film with copper, krypton and lead ions at 50 KeV xygen arbon ydrogen sputtering opper Krypton lead Effect of krypton Ion at Various Incidence Angles (30º-75º) Figure 2 (a, b, c and d) shows the ion beam energy (KeV) versus sputtering yield (Atom/Ion) of krypton ions at angles 30º, 45º, 60º and 75º on Polycarbonate/ polybutylene terephthalate film. It is found that the sputtering yield for hydrogen is the highest. This implies that, as the sputtered atomic number of element from Polycarbonate/ polybutylene terephthalate film is decreased, the sputtering yield is increased (a) (b) (c) (d) 0 Fig. (2): Ion beam energy (KeV) versus sputtering yield (Atom/Ion) of krypton ions by angle (a) 30º, (b) 45º, (c) 60º and (d) 75ºon Polycarbonate/ polybutylene terephthalate film. Figure( 3) shows the ion beam energy (KeV) versus the total sputtering yield (Atom / Ion) of krypton ions at angles 0º, 30º, 45º, 60º and 75º on Polycarbonate/ polybutylene terephthalate film. It is clear from this Figure 3 and Table (2) that at an energy of 45 KeV, the total sputtering yield is 2.153,

5 4.323, 7.447, and at angles 0º, 30º, 45º, 60º and 75º respectively, which means that as the ion beam incidence angle increases, the total sputtering yield increases. Table (2): Sputtering yields of oxygen, carbon and hydrogen for sputtering Polycarbonate/ polybutylene terephthalate film with krypton ions respectively at 45 KeV at incidence angles 30º, 45º, 60º and 75º. xygen arbon ydrogen 30º º º º angle 30 angle 45 angle 60 angle 75 angle 0 Fig. (3): Ion beam energy (KeV) versus total sputtering yield (Atom/Ion) of krypton ions at different incident angles on Polycarbonate/ polybutylene terephthalate film. 3- Integral Sputtered (SRIM Sputtering yield) The sputtering of the surface is described by its sputtering yield, which is defined as the mean number of sputtered target atoms per incident ion. If the target is made of several elements, and there is a separate sputtering yield for each element. Sputtering yield = (number of sputtered atoms)/(number of incident ions). ere, surface atoms are removed from the target by creating recoil cascades that come back out of the target, and which give surface atoms enough energy so that they are driven away from the target. There is a binding force which holds atoms to the target, and is called surface binding energy. An atom at the target surface is not confined on one side, so the energy required to remove it from its lattice site is less than if it was inside the solid and surrounded by other atoms. A surface atom has fewer electronic bonds which must to broken. TRIM calculates the integral sputtered which shows the energy of every recoiling atom from which reaches the target surface. The ordinate has units of atoms/ion, so each ion will produce about this number of recoiling atoms which reach the surface. Figure 4 (a-e) shows a vertical bar marked 3.8 ev, which is the average surface binding energy, that was entered for hydrogen in this target. In this Figure, there is an arrow to the left of this bar with the legend" not sputtered". At 3.8 ev, the number of atoms which reached the surface with more than this energy are 1, 2, 4, 7, and 18 for angles 0 º, 30 º, 45 º, 60 º and 75 º respectively.

6 angle = 0 o (a) angle = 30 o (b) angle = 45 o (c) angle = 60 o (d) angle = 75 o (e) Fig. (4): Surface energy (ev) versus sputtering yield (Atoms/Ion) of krypton ions with 45 kev at (a) 0 o, (b) 30 o, (c) 45 o, (d) 60 o and (e) 75 o angle on Polycarbonate/ polybutylene terephthalate film.

7 NLUSIN The sputtering yield for hydrogen, carbon and oxygen using different incidence angles, various energies and different elements was deduced. It is clear that at ion energy equals 50 KeV, the sputtering yield at an angle equal to 0º for oxygen is , and for copper, krypton and lead ions respectively. At at energy of 50 KeV, the sputtering yield for carbon equals , and for copper, krypton and lead ions respectively. At an energy of 50 KeV, the sputtering yield for hydrogen equals 1.2, 1.44 and 1.76 for copper, krypton and lead ions respectively. Then the total sputtering yield 50 KeV is 1.986, and for copper, krypton and lead ions respectively. It is found that the sputtering yield for hydrogen is the highest. This means that as the atomic number of element in the target is decreased, the sputtering yield is increased. Finally, it is concluded that the sputtering yield increases by decreasing the atomic number of the element in the target. Also it increases by increasing the ion beam energy and the incidence angle. REFERENES (1) adjichristov GB, Stefanov IL, Florian BI, Blaskova GD, Ivanov VG and Faulques E, Appl Surf Sci. 256, , (2009). (2) Fink D, Fundamentals of ion-irradiated polymers, Berlin: Springer-Verlag; (2004). (3) Kondyurin A and Bilek M, Ion beam treatment of polymers, UK: Elsevier; (2008). (4) Abdul-Kader AM, El-Badry BA, Zaki MF, egazy TM and ashem M, Philos Mag. 90, , (2010). (5) Teruyoshi M and J Rubber Soc Industry 76, , (2003). (6) Axisa, F., Schmitt, P.M., Gehin,., Delhomme, G., McAdams, E., Dittmar, A., IEEE Trans. Inf. Technol. Biomed. 9, 325, (2005). (7) Someya, T., Sekitani, T., Iba, S., Kato, Y., Kawaguchi,., Sakurai, T., Proc. Natl. Acad. Sci. U.S.A. 101, 9966, (2004). (8) adjichristov GB, Gueorguiev VK, Ivanov TE, Marinov YG, Ivanov VG, Faulques E, rg Electron 9, , (2008). (9) imanshu AK, Bandyopadhayay SK, Sen P, Mondal NN, Talpatra A, Taki GS, et al, Radiat Phys hem. 80, , (2011). (10) Niklaus M and Shea R, Acta Mater. 59, , (2011). (11) Girolamo GD, Massaro M, Piscopiello E and tapfer L, Nucl Instrum Methods B 268, , (2011). (12) Wang YQ, Nucl Instrum Methods B, , , (2000). (13) Ahmed SF, Yi JW, Moon M-W, Jang Y-J, Park B-, Lee S-, et al., Plasma Process Polym; 6, , (2009). (14) Manso M, Navas R, Gilliland D, Ruiz PG and Rossi F, Acta Biomater. 35, , (2007). (15) Van Krevelen DW, In: Te Nijenhuis K, editor. Properties of polymers, 4th ed.; p , (2009). (16) Radwan RM, Abdul-Kader AM and El-ag Ali A, Nucl Instrum Methods B 266, , (2008). (17) Popok V.N., Rev. Adv. Mater. Sci. 30, 1, (2012). (18) Abdel Salam, M.., Nouh, S.A., Radwan, E.Y., Fouad, S.S., Mater. hem. Phys. 127, 305, (2011). (19) Goyal P.K., Kumar V., Gupta R., Mahendia S., Anita and Kumar S., Vacuum 86, 1087, (2012). 399

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