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Ion beam analysis of light elements in nanoporous surfaces produced by single- and multiple-energy helium ion implantation
Nuclear Instruments and Methods in Physics Research B 190 (2002) 718–722 www.elsevier.com/locate/nimb
Ion beam analysis of light elements in nanoporous surfaces produced by single- and multiple-energy helium ion implantation A. Markwitz a
a,*
, P.B. Johnson b, P.W. Gilberd b, G.A. Collins
c
Institute of Geological and Nuclear Sciences Ltd., 30 Gracefield Road, P.O. Box 31-312, Lower Hutt, New Zealand b Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand c ANSTO, Materials Division, Private Mail Bag 1, Menai, NSW 2234, Australia
Abstract Helium ion implantation into surfaces is used to form nanoporous cavity structures at high dose levels. Such cavity structures have unique features which offer potential for applications. For some applications, it is necessary to produce cavity layers that extend to the surface to enhance the ingress of selected dopant atoms. Here we investigate a method based on using a He-implantation protocol (employing a combination of He energies and doses) to produce nanoporous layers that intersect the surface. Titanium and other targets are implanted with He to several different dose levels and at several different energies. Implantations employing several different He energies in sequence are also investigated. Light atom depth profiles are determined by heavy ion elastic recoil detection analysis (HERDA). Non-resonant nuclear reaction analysis is used to verify the absolute concentrations of carbon, nitrogen and oxygen. RBS is used to depth profile the corresponding heavy target elements. Selected results, chosen to highlight the potential of HERDA and other ion beam analysis techniques in this type of study, are presented. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 61.82.Bg; 61.72.Qq; 61.16.Bg; 28.52.Fa Keywords: He-implantation; PI3 e; Ion beam analysis; HERDA; Titanium
1. Introduction Helium ion implantation into metals leads to the formation of bubble structures in the implanted layer [1–4]. At high dose levels nanoporous cavity structures can be formed. Such structures, and the compounds that can be formed *
Corresponding author. Tel.: +64-4-570-4637; fax: +64-4570-4657. E-mail address: [email protected] (A. Markwitz).
on them, have unique features of interest for applications. Previous studies [5–9] concentrated on monoenergetic implantations using He energies that produced the cavity structures in a buried layer below the surface. However, for most applications cavity layers that extend to the surface will be needed so as to enhance the ingress of desired dopant atoms. The approach investigated here is based on using a He-implantation protocol (employing a combination of He energies and doses) to produce a nanoporous layer that intersects the
0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 0 1 ) 0 1 1 9 8 - 3
A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
surface. Here, we investigate the application of light element depth profiling using heavy ion elastic recoil detection analysis (HERDA) [7,8] supplemented by other ion beam analysis (IBA) techniques [6,8]. Titanium, Co, Si and Au targets have been implanted with He using pulsed plasma-immersion ion-implantation (PI3 e) [8,10] to several different dose levels and at several different energies. Also implantations employing several He energies in sequence are investigated. Also, accelerator implantations at the higher energy of 160 keV (with the incident ion beam at 60° to the surface normal) have been used to extend the depth range covered. The high-resolution HERDA depth profiles for H, He, C, N, O and Ti were measured using an 82 MeV incident iodine beam and a recoil timeof-flight system. The angle between the beam and the recoil particles was 45°. The recoil energies were measured with a surface-barrier detector. The detection sensitivity is comparable to RBS. The high depth resolution (10 nm) makes HERDA a powerful technique for thin layer studies. 2. Previous research Information on the dependence of bubble structure on He fluence and the depth below the implanted metal surface is based principally on TEM [1–9] and XTEM [2,3,8,11] techniques. For metals implanted at temperatures 0.2Tm (where Tm is the melting temperature of the metal in degrees K) previous studies suggest that there is a universal response of metals to He-implantation. The theoretical depth profile of implanted He calculated for a monoenergetic incident beam using Monte-Carlo programmes, such as TRIM [12], is a broad bell-shaped curve centred (approximately) on the mean projected range, Rp . There is now strong support for the following model for the evolution of bubble structure at depths near Rp . 3. Model of bubble development Bubbles nucleate randomly at low He concentrations. The average bubble size increases monotonically with dose and patches of ordered bubbles
719
develop in localized regions of the array. For local He concentrations 10–15 at.% the bubbles are ordered on a space lattice – a gas bubble superlattice. Typical bubble sizes are 2 nm and bubble lattice parameters are 6 nm. For local He concentrations 20 at.% the bubble array is cellular in structure with most bubble cavities still separated from their neighbours. Further implantation results in a coarsening of the bubble array until the size of the most commonly occurring bubbles reaches 6–8 nm where the cavity structure becomes nanoporous [1,3,5,9]. Increasing He fluence leads to radiation blistering of the target surface [3]. At the critical dose the He concentration at depths near Rp is 30 at.%. In this model the volume fraction of bubble cavities at any given depth depends solely on the concentration of He at that depth. This suggests the degree of cavitation as a function of depth can be deduced simply from experimentally determined He depth profiles. The present work was undertaken to evaluate this approach for testing He-implantation protocols aimed at producing nanoporous layers extending to the implanted surface.
4. Results and discussion To focus on evaluating the application of IBA techniques in this type of study only the results for Ti are presented, although four representative materials: Ti, Co, Si and Au, were investigated. The qualitative He depth profiles determined by HERDA are shown in Fig. 1 for implantations at four different He energies. An approximate depth scale can be derived by comparing the deeper edges of the profiles with TRIM predictions. It is estimated that channel 475 corresponds to a depth 350 nm and that the response is approximately linear over the depth range from the surface (channel 568) to this depth. The response at greater depths is increasingly uncertain owing to factors such as surface roughness and multiple scattering. For the PI3 implantations, the front (near-surface) part of each profile contains a greater amount of He than expected from TRIM. This
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A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
Fig. 1. He depth profiles (using HERDA) in Ti targets following monoenergetic PI3 He-implantations at normal incidence for three energies 6, 20 and 40 keV, and an accelerator implantation at 160 keV with the ion beam at 60° to the surface normal. The nominal fluences for the four implantations are, in units of 1017 Heþ cm2 : 4, 6, 8 and 10, respectively.
may be caused by enhanced diffusion of He into the damage profile at the high He fluences involved although factors associated with PI3 implantations cannot be ruled out. The ratio of He counts in the profile to implanted fluence is constant for these three implants. This indicates that a high proportion of the implanted He is being retained in the target. Qualitative oxygen depth profiles, determined following the 6 and 40 keV He implantations of Fig. 1, are shown in Fig. 2. For the 6 keV implantation, there is a surface peak and considerable oxygen below the surface. In contrast, for the 40 keV implantation, there is negligible oxygen below the surface. This suggests that the increased cavitation near the surface in the 6 keV He implantation has enhanced the ingress of oxygen into the target. For a He-implant energy of 40 keV, the results of Fig. 1 imply that all the implanted He is retained in the target and the profile shape is maintained up to a fluence of 8 1017 Heþ cm2 . Fig. 3 shows the profiles for four fluences. The ratio of He counts to He fluence is constant up to 8 1017 Heþ cm2 . However, for a fluence of 12 1017 Heþ cm2 , the ratio drops to about 70% of its previous value. It seems that at the higher
Fig. 2. Qualitative oxygen depth profiles in Ti determined by HERDA for two of the He-implanted targets of Fig. 1. The first profile ( ) is from the target implanted at 6 keV, whereas the second profile ( ) is from the target implanted at 40 keV. In the first case there is a considerable level of oxygen held below the surface. Both targets exhibit a surface peak.
Fig. 3. He depth profiles (using HERDA) in Ti targets following monoenergetic He-implantations at normal incidence for an energy of 40 keV to several different fluences. The fluences are respectively (in units of 1017 Heþ cm2 ): 1, 3, 8 and 12.
fluence an appreciable fraction of the implanted He has been lost. The double-peaked structure shows that the He has been lost mainly from the middle of the profile – a depth region centred around Rp . The loss is attributed [3,9] to the onset of nanoporosity in the implanted layer coupled with radiation blistering providing escape routes to the surface.
A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
To investigate the effects of multiple-energy implantations, a single Ti target was implanted in sequence with He at 6, 20 and 40 keV to the same individual fluences as the single-energy PI3 implantations of Fig. 1. The He profile for the multiple-energy implantation is shown together with the single-energy profiles in Fig. 4. It is clear that the profile for the multiple-energy implantation is much less than the sum of the three individual single-energy profiles. The difference is most pronounced near the surface, showing that a high proportion of the He from the 6 and 20 keV implants has been lost from the multiple-energy implant. This is attributed to the local He concentration in the near-surface regions rising to the level required to produce nanoporosity and the escape of He from the front of the profile. SEM examination of this target shows radiation blistering of the surface has occurred. Other IBA techniques were applied, as in previous work [7]. Non-resonant nuclear reaction analysis (NRA) was used to verify the absolute concentrations of C, N and O. RBS was employed to depth profile the corresponding heavy target element. Of particular interest was the oxygen content of the two He-implanted targets of Fig. 2.
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NRA shows that in the first micrometer of the specimens the oxygen content of the 6 keV target is more than a factor of 2 greater than that for the 40 keV target. This agrees with the profiles of Fig. 2. More generally, for the different target materials studied, the NRA and RBS results were consistent with the HERDA profiles. In conclusion, HERDA can provide valuable information for assessing He-implantation protocols aimed at tailoring nanoporous surfaces for particular applications. The He profiles allow the onset and extent of nanoporosity in the implanted layer to be deduced. The degree of penetration of light atoms such as O, N and C into the surface can be found from the corresponding profiles collected concurrently. Absolute amounts of these elements, at the levels found in He-implanted targets, can be determined using NRA and RBS. IBA techniques provide a powerful complement to electron microscopy in the study of He-implanted surfaces.
Acknowledgements This work was done under research contracts to the New Zealand Foundation for Research, Science and Technology and grants from the Australian Institute of Nuclear Science and Engineering. We thank Dr. D. Cohen and Dr. N. Dytleswki of ANSTO, C.R. Varoy from Victoria University of Wellington and W.J. Trompetter and C. Purcell from the Institute of Geological and Nuclear Sciences.
References
Fig. 4. He depth profiles (using HERDA) in Ti targets following single-energy implantations for three energies 6, 20 and 40 keV and the profile for a Ti target implanted in sequence with He to the same individual energies and fluences as used in the single-energy implantations. The sum curve of the singleenergy implantations is shown for comparison.
[1] P.B. Johnson, in: J.H. Evans, S.E. Donnelly (Eds.), Fundamental Aspects of Inert Gases in Solids, Plenum Press, New York, 1991, p. 167. [2] P.B. Johnson, K.L. Reader, R.W. Thomson, J. Nucl. Mater. 23 (1996) 92. [3] P.B. Johnson, R.W. Thomson, K. Reader, J. Nucl. Mater. 273 (1999) 117. [4] P.B. Johnson, P.W. Gilberd, Y. Morrison, C.R. Varoy, Mod. Phys. Lett. B 15 (2001) 1391. [5] P.W. Gilberd, P.B. Johnson, I.C. Vickridge, Nucl. Instr. and Meth. B 127/128 (1997) 738.
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A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
[6] I.C. Vickridge, P.B. Johnson, P.W. Gilberd, Y. Morrison, Nucl. Instr. and Meth. B 136/138 (1998) 1068. [7] A. Markwitz, P.B. Johnson, P.W. Gilberd, G.A. Collins, D.D. Cohen, N. Dytlewski, Nucl. Instr. and Meth. B 161/ 163 (2000) 1048. [8] P.B. Johnson, P.W. Gilberd, A. Markwitz, W.J. Trompetter, G.A. Collins, K.T. Short, D.D. Cohen, N. Dytlewski, Surf. Coat. Technol. 136 (2001) 217.
[9] P.B. Johnson, A. Markwitz, P.W. Gilberd, Adv. Mater. 13 (2001) 997. [10] G.A. Collins, R. Hutchings, K.T. Short, J. Tendys, Surf. Coat. Technol. 104 (1998) 212. [11] P.B. Johnson, D.J. Mazey, J. Nucl. Mater. 111/112 (1982) 681. [12] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Matter, Pergamon Press, New York, 1985.
Ion beam analysis of light elements in nanoporous surfaces produced by single- and multiple-energy helium ion implantation A. Markwitz a
a,*
, P.B. Johnson b, P.W. Gilberd b, G.A. Collins
c
Institute of Geological and Nuclear Sciences Ltd., 30 Gracefield Road, P.O. Box 31-312, Lower Hutt, New Zealand b Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand c ANSTO, Materials Division, Private Mail Bag 1, Menai, NSW 2234, Australia
Abstract Helium ion implantation into surfaces is used to form nanoporous cavity structures at high dose levels. Such cavity structures have unique features which offer potential for applications. For some applications, it is necessary to produce cavity layers that extend to the surface to enhance the ingress of selected dopant atoms. Here we investigate a method based on using a He-implantation protocol (employing a combination of He energies and doses) to produce nanoporous layers that intersect the surface. Titanium and other targets are implanted with He to several different dose levels and at several different energies. Implantations employing several different He energies in sequence are also investigated. Light atom depth profiles are determined by heavy ion elastic recoil detection analysis (HERDA). Non-resonant nuclear reaction analysis is used to verify the absolute concentrations of carbon, nitrogen and oxygen. RBS is used to depth profile the corresponding heavy target elements. Selected results, chosen to highlight the potential of HERDA and other ion beam analysis techniques in this type of study, are presented. Ó 2002 Elsevier Science B.V. All rights reserved. PACS: 61.82.Bg; 61.72.Qq; 61.16.Bg; 28.52.Fa Keywords: He-implantation; PI3 e; Ion beam analysis; HERDA; Titanium
1. Introduction Helium ion implantation into metals leads to the formation of bubble structures in the implanted layer [1–4]. At high dose levels nanoporous cavity structures can be formed. Such structures, and the compounds that can be formed *
Corresponding author. Tel.: +64-4-570-4637; fax: +64-4570-4657. E-mail address: [email protected] (A. Markwitz).
on them, have unique features of interest for applications. Previous studies [5–9] concentrated on monoenergetic implantations using He energies that produced the cavity structures in a buried layer below the surface. However, for most applications cavity layers that extend to the surface will be needed so as to enhance the ingress of desired dopant atoms. The approach investigated here is based on using a He-implantation protocol (employing a combination of He energies and doses) to produce a nanoporous layer that intersects the
0168-583X/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 0 1 ) 0 1 1 9 8 - 3
A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
surface. Here, we investigate the application of light element depth profiling using heavy ion elastic recoil detection analysis (HERDA) [7,8] supplemented by other ion beam analysis (IBA) techniques [6,8]. Titanium, Co, Si and Au targets have been implanted with He using pulsed plasma-immersion ion-implantation (PI3 e) [8,10] to several different dose levels and at several different energies. Also implantations employing several He energies in sequence are investigated. Also, accelerator implantations at the higher energy of 160 keV (with the incident ion beam at 60° to the surface normal) have been used to extend the depth range covered. The high-resolution HERDA depth profiles for H, He, C, N, O and Ti were measured using an 82 MeV incident iodine beam and a recoil timeof-flight system. The angle between the beam and the recoil particles was 45°. The recoil energies were measured with a surface-barrier detector. The detection sensitivity is comparable to RBS. The high depth resolution (10 nm) makes HERDA a powerful technique for thin layer studies. 2. Previous research Information on the dependence of bubble structure on He fluence and the depth below the implanted metal surface is based principally on TEM [1–9] and XTEM [2,3,8,11] techniques. For metals implanted at temperatures 0.2Tm (where Tm is the melting temperature of the metal in degrees K) previous studies suggest that there is a universal response of metals to He-implantation. The theoretical depth profile of implanted He calculated for a monoenergetic incident beam using Monte-Carlo programmes, such as TRIM [12], is a broad bell-shaped curve centred (approximately) on the mean projected range, Rp . There is now strong support for the following model for the evolution of bubble structure at depths near Rp . 3. Model of bubble development Bubbles nucleate randomly at low He concentrations. The average bubble size increases monotonically with dose and patches of ordered bubbles
719
develop in localized regions of the array. For local He concentrations 10–15 at.% the bubbles are ordered on a space lattice – a gas bubble superlattice. Typical bubble sizes are 2 nm and bubble lattice parameters are 6 nm. For local He concentrations 20 at.% the bubble array is cellular in structure with most bubble cavities still separated from their neighbours. Further implantation results in a coarsening of the bubble array until the size of the most commonly occurring bubbles reaches 6–8 nm where the cavity structure becomes nanoporous [1,3,5,9]. Increasing He fluence leads to radiation blistering of the target surface [3]. At the critical dose the He concentration at depths near Rp is 30 at.%. In this model the volume fraction of bubble cavities at any given depth depends solely on the concentration of He at that depth. This suggests the degree of cavitation as a function of depth can be deduced simply from experimentally determined He depth profiles. The present work was undertaken to evaluate this approach for testing He-implantation protocols aimed at producing nanoporous layers extending to the implanted surface.
4. Results and discussion To focus on evaluating the application of IBA techniques in this type of study only the results for Ti are presented, although four representative materials: Ti, Co, Si and Au, were investigated. The qualitative He depth profiles determined by HERDA are shown in Fig. 1 for implantations at four different He energies. An approximate depth scale can be derived by comparing the deeper edges of the profiles with TRIM predictions. It is estimated that channel 475 corresponds to a depth 350 nm and that the response is approximately linear over the depth range from the surface (channel 568) to this depth. The response at greater depths is increasingly uncertain owing to factors such as surface roughness and multiple scattering. For the PI3 implantations, the front (near-surface) part of each profile contains a greater amount of He than expected from TRIM. This
720
A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
Fig. 1. He depth profiles (using HERDA) in Ti targets following monoenergetic PI3 He-implantations at normal incidence for three energies 6, 20 and 40 keV, and an accelerator implantation at 160 keV with the ion beam at 60° to the surface normal. The nominal fluences for the four implantations are, in units of 1017 Heþ cm2 : 4, 6, 8 and 10, respectively.
may be caused by enhanced diffusion of He into the damage profile at the high He fluences involved although factors associated with PI3 implantations cannot be ruled out. The ratio of He counts in the profile to implanted fluence is constant for these three implants. This indicates that a high proportion of the implanted He is being retained in the target. Qualitative oxygen depth profiles, determined following the 6 and 40 keV He implantations of Fig. 1, are shown in Fig. 2. For the 6 keV implantation, there is a surface peak and considerable oxygen below the surface. In contrast, for the 40 keV implantation, there is negligible oxygen below the surface. This suggests that the increased cavitation near the surface in the 6 keV He implantation has enhanced the ingress of oxygen into the target. For a He-implant energy of 40 keV, the results of Fig. 1 imply that all the implanted He is retained in the target and the profile shape is maintained up to a fluence of 8 1017 Heþ cm2 . Fig. 3 shows the profiles for four fluences. The ratio of He counts to He fluence is constant up to 8 1017 Heþ cm2 . However, for a fluence of 12 1017 Heþ cm2 , the ratio drops to about 70% of its previous value. It seems that at the higher
Fig. 2. Qualitative oxygen depth profiles in Ti determined by HERDA for two of the He-implanted targets of Fig. 1. The first profile ( ) is from the target implanted at 6 keV, whereas the second profile ( ) is from the target implanted at 40 keV. In the first case there is a considerable level of oxygen held below the surface. Both targets exhibit a surface peak.
Fig. 3. He depth profiles (using HERDA) in Ti targets following monoenergetic He-implantations at normal incidence for an energy of 40 keV to several different fluences. The fluences are respectively (in units of 1017 Heþ cm2 ): 1, 3, 8 and 12.
fluence an appreciable fraction of the implanted He has been lost. The double-peaked structure shows that the He has been lost mainly from the middle of the profile – a depth region centred around Rp . The loss is attributed [3,9] to the onset of nanoporosity in the implanted layer coupled with radiation blistering providing escape routes to the surface.
A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
To investigate the effects of multiple-energy implantations, a single Ti target was implanted in sequence with He at 6, 20 and 40 keV to the same individual fluences as the single-energy PI3 implantations of Fig. 1. The He profile for the multiple-energy implantation is shown together with the single-energy profiles in Fig. 4. It is clear that the profile for the multiple-energy implantation is much less than the sum of the three individual single-energy profiles. The difference is most pronounced near the surface, showing that a high proportion of the He from the 6 and 20 keV implants has been lost from the multiple-energy implant. This is attributed to the local He concentration in the near-surface regions rising to the level required to produce nanoporosity and the escape of He from the front of the profile. SEM examination of this target shows radiation blistering of the surface has occurred. Other IBA techniques were applied, as in previous work [7]. Non-resonant nuclear reaction analysis (NRA) was used to verify the absolute concentrations of C, N and O. RBS was employed to depth profile the corresponding heavy target element. Of particular interest was the oxygen content of the two He-implanted targets of Fig. 2.
721
NRA shows that in the first micrometer of the specimens the oxygen content of the 6 keV target is more than a factor of 2 greater than that for the 40 keV target. This agrees with the profiles of Fig. 2. More generally, for the different target materials studied, the NRA and RBS results were consistent with the HERDA profiles. In conclusion, HERDA can provide valuable information for assessing He-implantation protocols aimed at tailoring nanoporous surfaces for particular applications. The He profiles allow the onset and extent of nanoporosity in the implanted layer to be deduced. The degree of penetration of light atoms such as O, N and C into the surface can be found from the corresponding profiles collected concurrently. Absolute amounts of these elements, at the levels found in He-implanted targets, can be determined using NRA and RBS. IBA techniques provide a powerful complement to electron microscopy in the study of He-implanted surfaces.
Acknowledgements This work was done under research contracts to the New Zealand Foundation for Research, Science and Technology and grants from the Australian Institute of Nuclear Science and Engineering. We thank Dr. D. Cohen and Dr. N. Dytleswki of ANSTO, C.R. Varoy from Victoria University of Wellington and W.J. Trompetter and C. Purcell from the Institute of Geological and Nuclear Sciences.
References
Fig. 4. He depth profiles (using HERDA) in Ti targets following single-energy implantations for three energies 6, 20 and 40 keV and the profile for a Ti target implanted in sequence with He to the same individual energies and fluences as used in the single-energy implantations. The sum curve of the singleenergy implantations is shown for comparison.
[1] P.B. Johnson, in: J.H. Evans, S.E. Donnelly (Eds.), Fundamental Aspects of Inert Gases in Solids, Plenum Press, New York, 1991, p. 167. [2] P.B. Johnson, K.L. Reader, R.W. Thomson, J. Nucl. Mater. 23 (1996) 92. [3] P.B. Johnson, R.W. Thomson, K. Reader, J. Nucl. Mater. 273 (1999) 117. [4] P.B. Johnson, P.W. Gilberd, Y. Morrison, C.R. Varoy, Mod. Phys. Lett. B 15 (2001) 1391. [5] P.W. Gilberd, P.B. Johnson, I.C. Vickridge, Nucl. Instr. and Meth. B 127/128 (1997) 738.
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A. Markwitz et al. / Nucl. Instr. and Meth. in Phys. Res. B 190 (2002) 718–722
[6] I.C. Vickridge, P.B. Johnson, P.W. Gilberd, Y. Morrison, Nucl. Instr. and Meth. B 136/138 (1998) 1068. [7] A. Markwitz, P.B. Johnson, P.W. Gilberd, G.A. Collins, D.D. Cohen, N. Dytlewski, Nucl. Instr. and Meth. B 161/ 163 (2000) 1048. [8] P.B. Johnson, P.W. Gilberd, A. Markwitz, W.J. Trompetter, G.A. Collins, K.T. Short, D.D. Cohen, N. Dytlewski, Surf. Coat. Technol. 136 (2001) 217.
[9] P.B. Johnson, A. Markwitz, P.W. Gilberd, Adv. Mater. 13 (2001) 997. [10] G.A. Collins, R. Hutchings, K.T. Short, J. Tendys, Surf. Coat. Technol. 104 (1998) 212. [11] P.B. Johnson, D.J. Mazey, J. Nucl. Mater. 111/112 (1982) 681. [12] J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Matter, Pergamon Press, New York, 1985.