- Email: [email protected]
Study of the damage produced in silicon carbide by high energy heavy ions
Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Study of the damage produced in silicon carbide by high energy heavy ions A. Benyagoub *, A. Audren CIMAP (ex-CIRIL-GANIL), CEA-CNRS-ENSICAEN-Université de Caen Basse Normandie, Bd Henri Becquerel, BP 5133, F-14070 Caen cedex 5, France
a r t i c l e
i n f o
Article history: Available online 21 February 2009 PACS: 61.80.x 61.80.Jh Keywords: Silicon carbide Ion radiation effects Radiation damage Optical defects Optical absorption
a b s t r a c t Silicon carbide (SiC) single crystals were irradiated at room temperature with different ion species of several hundreds MeV in order to explore a wide range of the deposited electronic and nuclear energy losses. The samples were characterized by optical absorption spectroscopy. The comparison of the transmittance data obtained after irradiation with different ion species in combination with the use of energy degraders of different thicknesses allowed to demonstrate that the optical defects created by swift heavy ions are essentially produced by elastic collisions and occur mainly at the end of the ion range region. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Silicon carbide (SiC) has drawn large interest in the last decades for its various potential technological applications. Due to its wide band gap and its outstanding thermal, electrical and optical properties, SiC is a promising material for high-temperature electronic and optoelectronic devices [1–4]. Moreover, due to its low neutron absorption cross-section and its good mechanical properties and chemical inertness, SiC is also potentially useful for the nuclear industry, either as a cladding material for the nuclear fuel in the future fission reactors or as a protective coating for the first wall in fusion technology [5,6]. Several papers reported on radiation effects induced in SiC by various kinds of energetic particles [7–11]. However, very few studies were devoted to the effects induced by swift heavy ions in this material. The aim of this contribution is to present recent results describing the damage produced in 6H-SiC single crystals by different heavy ions accelerated at several hundreds MeV. Since with such particles the thickness of the bombarded layer extends over a few tens of micrometers, optical absorption spectroscopy in the UV–visible range was chosen for the characterization of the induced damage. This technique is, in fact, well suited for probing thick samples and is also very sensitive for the detection of low defect concentrations. However, it cannot provide the depth distribution of the detected defects. In this study, this drawback
* Corresponding author. Tel.: +33 2 31 45 45 73; fax: +33 2 31 45 47 14. E-mail address: [email protected] (A. Benyagoub). 0168-583X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2009.01.026
was partly overcome by using energy degraders of different thicknesses. 2. Experimental The samples with dimensions of 10 10 mm2 were cut from a single crystalline (0 0 0 1)-oriented 6H-SiC wafer optically polished on both sides and having a thickness of 250 lm. All the samples were partly capped by a 250-lm thick Cu foil in order to preserve virgin areas for calibration. They were irradiated at room temperature with 300-MeV Ni, 910-MeV Xe or 860-MeV Pb ions delivered by the ‘‘Medium Energy Exit” of the GANIL accelerator in Caen (France). The ion range Rp of these ion species is, respectively, 30.9, 48.4 and 33.5 lm. During irradiation, the ion flux was deliberately set below 3 108 ion cm2 s1 in order to prevent target heating. For the irradiations with Xe and Pb ions, some samples were covered by aluminium foils of different thicknesses. The purpose of these aluminium foils (‘energy degraders’) is to decrease the ion energy at the entrance of the SiC specimens and thus to reduce the depth of the bombarded layers. All the samples were characterized after ion irradiation by UV–visible absorption spectroscopy. 3. Results and discussion The transmittance spectra recorded after irradiation with different fluences of Ni, Xe and Pb ions are presented in Fig. 1 together with some spectra registered on the unirradiated part of some samples. The transmittance of the virgin areas is practically zero
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A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
the sample irradiated at the fluence U. Eq. (1) provides for each irradiated sample the increase in absorbance caused by the damage produced by the ion irradiation. The transmittance data shown in Fig. 1 were analyzed with Eq. (1), and the obtained values of the increase in absorbance are presented in Fig. 2 with the ion fluence as a parameter. In fact, the different curves of the figure are normalized to the fluence of 1011 ion cm2 in order to facilitate their comparison. This normalization was accomplished by dividing Eq. (1) by the fluence U given in the units of 1011 ion cm2. It appears that for each type of ion irradiation the corresponding curves can almost be merged in a single one. This result indicates that the increase in absorbance is directly proportional to the ion fluence. It also points out that there is no noticeable saturation in the concentration of optically absorbing centers created by ion irradiation, at least in the fluence range explored in this study. One can also notice that the increase in absorbance is all the more pronounced the higher the mass of the irradiating ion indicating that Pb ions induce much more damage than Xe and Ni ions.
Fig. 1. Transmittance spectra recorded on SiC single crystals irradiated at room temperature with different fluences of 300-MeV Ni (a), 910-MeV Xe (b) and 860MeV Pb (c) ions. Some spectra recorded on the unirradiated part of some samples are also shown for comparison.
below the wavelength of 400 nm and then increases abruptly above that wavelength to attain a value around 0.6. This behavior is consistent with similar measurements reported in the literature [12,13]. The small dip appearing around 630 nm very likely originates from the initial nitrogen doping of the as-received SiC wafer [12]. After irradiation, the transmittance decreases all over the wavelength range with increasing ion fluence, whatever the ion species. Also, the absorption edge becomes broader and is shifted towards higher wavelengths due to the generation by the ion irradiation of defect levels located within the band gap. If one neglects the modification brought to the reflectivity by ion bombardment, the change of absorbance in the irradiated material with respect to that of the virgin one is given by:
DAðUÞ ¼ AðUÞ Av irgin ¼ ln
T v irgin ; TðUÞ
ð1Þ
where Avirgin, Tvirgin, A(U) and T(U) are, respectively, the absorbance and the transmittance in the virgin and in the bombarded part of
Fig. 2. Change in absorbance in the SiC samples irradiated at room temperature with different fluences of 300-MeV Ni (a), 910-MeV Xe (b) and 860-MeV Pb (c) ions. The curves are normalized to the fluence of 1011 ion cm2 for the purpose of comparison. This was obtained by dividing their original height (as deduced from Eq. (1)) by the fluence given in the units of 1011 ion cm2 (the normalization factor is indicated between brackets for each curve).
A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
Fig. 3. Similarity of the transmittance curves obtained on SiC samples irradiated with 1013 Ni cm2, 2 1012 Xe cm2 or 1012 Pb cm2.
This effect of the ion mass can also be observed directly by comparing the transmittance curves obtained after irradiation with 1013 Ni cm2, 2 1012 Xe cm2 and 1012 Pb cm2 (see Fig. 3). It is remarkable that these three samples, while irradiated with different ion species at different fluences, exhibit almost the same transmittance indicating that the total amount of optically absorbing centers is the same in these samples. The comparison of the ion fluence necessary to attain this amount of disorder points out that Pb ions are almost two times more efficient than Xe ions and nearly ten times more efficient than Ni ions for creating damage in SiC. It is then interesting to address the origin of this difference. According to the TRIM code [14], the total amount of energy lost in electronic excitations for 300-MeV Ni, 910-MeV Xe and 860-MeV Pb ions is, respectively, 298 MeV, 903 MeV and 846 MeV. Obviously, Xe ions induce much more electronic excitations than Pb ions while they are two times less efficient in creating damage. Therefore, the latter cannot be accounted for by electronic excitations. On the other hand, the total amount of energy lost by nuclear
1257
collisions is about 1.6 MeV for 300-MeV Ni, 7 MeV for 910-MeV Xe and 14 MeV for 860-MeV Pb. These values of the nuclear energy loss scale remarkably well with the efficiency of the corresponding ion species. This result is clear evidence that the optically absorbing centers are essentially created by nuclear collisions. Therefore, their distribution inside the irradiated samples is expected to follow the nuclear energy loss profile. Since the irradiating particles are swift heavy ions, nuclear collisions and thus optically absorbing centers are for the major part distributed deeply inside the samples, in the vicinity of the end of range (i.e. Rp) of the incident ions. In order to check definitely if the optical defects are created near the end of range of the irradiating ions, some SiC samples were covered with aluminium foils acting as energy degraders. In the case of Xe irradiation, two thicknesses were selected: 28 and 42 lm. The first one decreased the incident ion energy down to an average value of 470 MeV at the entrance of the irradiated SiC specimen, reducing then the thickness of the bombarded layer by 21 lm. The second one reduced the ion energy down to 235 MeV and thus decreased the effective thickness of the bombarded layer by 32 lm. Fig. 4 illustrates the evolution with depth of the electronic and nuclear energy losses released by the irradiating Xe ion in these different configurations. In the case of the irradiation without energy degrader, the Xe ion moves across region 1 (21 lm) and region 2 (11 lm) and then stops near the end of region 3 (16 lm). With the use of the 28-lm Al degrader, the ion traverses region 2 and comes at rest near the end of region 3; whereas in the case of the 42-lm Al degrader, the ion travels only in region 3. The transmittance spectra recorded on these samples are presented in Fig. 5 in the case of the irradiation with the fluence of 1012 Xe cm2. The transmittance of a virgin sample is also shown for the purpose of comparison. It clearly appears that the spectra obtained on the irradiated specimens are nearly the same. This result indicates that the change in transmittance is mainly due to the radiation damage occurring in region 3 (i.e. within the end of the ion range region) and that the contribution of region 1 and region 2, where the electronic energy loss is as high as 22 keV nm1, is insignificant. These are evidence that electronic excitations released by swift heavy ions do not create detectable amount of optical defects in SiC. The latter are located predominantly at the end of the ion range region and are thus ascribed essentially to nuclear collisions. Similar results (not shown) were
Fig. 4. Schematic view illustrating the evolution with depth of the electronic and nuclear energy losses released by a 910-MeV Xe ion in SiC with and without the use of energy degraders. The latter are Al foils of 28 and 42 lm.
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A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
defects cannot be accounted for by the huge amount of electronic excitations and ionizations released in the wake of the irradiating ions. Instead, it appears that this disorder is essentially created by nuclear collisions. Both results were confirmed by specific experiments involving energy degraders, which allowed to probe different depths. It is shown that the created optical defects are, for the major part, distributed deeply inside the irradiated samples, i.e. in the vicinity of the end of range region of the incident ions. This result could be of interest for some applications necessitating the modification of the optical properties of SiC deeply below the surface, at any desired depth limited only by the accessible ion energy, with the advantage of not altering shallower regions. Acknowledgements This work was partly supported by the following french research organizations: CPR ISMIR, GdR GEDEPEON and GdR MATINEX. References Fig. 5. Transmittance spectra recorded after irradiation with 910-MeV Xe ions at the same fluence of 1012 Xe cm2 with and without the use of energy degraders. A spectrum registered on a virgin sample is also shown for comparison.
also obtained using energy degraders in the case of the irradiation with 860-MeV Pb ions.
[1] [2] [3] [4] [5] [6] [7]
4. Conclusion The transmittance data obtained on SiC single crystals irradiated with different swift heavy ions indicate that the produced disorder is proportional to the ion fluence for each ion species, suggesting that there is no defect saturation at least in the fluence range explored in this study (i.e. up to 1013 ion cm2). The comparison of these transmittance data points out that the created optical
[8] [9] [10] [11] [12] [13] [14]
J.W. Palmorn, H.S. Kong, R.F. Davies, Appl. Phys. Lett. 51 (1987) 2028. J.A. Edward, K. Das, R.F. Davies, J. Appl. Phys. 63 (1988) 922. K. Shnai, R.S. Scott, B.J. Baliga, IEEE Trans. Electron Dev. ED-36 (1989) 1811. H. Morkoç, S. Strite, G.B. Gao, M.E. Lin, B. Sverdlov, M. Burns, J. Appl. Phys. 76 (1994) 1363. L.H. Ford, N.S. Hibbert, D.G. Martin, J. Nucl. Mater. 45 (1972) 139. P. Fenici, A.J. Rebelo, R.H. Jones, A. Kobyama, L.L. Snead, J. Nucl. Mater. 258 (1998) 215. K. Yasuda, M. Takeda, H. Masuda, A. Yoshida, Phys. Status Solidi (a) 71 (1982) 549. C.J. McHargue, J.M. Williams, Nucl. Instr. and Meth. B 80–81 (1993) 889. E. Wendler, A. Heft, W. Wesch, Nucl. Instr. and Meth. B 141 (1998) 105. W.J. Weber, L.M. Wang, N. Yu, N.J. Hess, Mater. Sci. Eng. A 253 (1998) 62. L.L. Snead, S.J. Zinkle, Nucl. Instr. and Meth. B 191 (2002) 497. E. Wendler, A. Heft, U. Zammit, E. Glaser, M. Marinelli, W. Wesch, Nucl. Instr. and Meth. B 116 (1996) 398. L. Calcagno, M.G. Grimaldi, P. Musumeci, J. Mater. Res. 12 (1997) 1727. J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon, New York, 1985.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
Study of the damage produced in silicon carbide by high energy heavy ions A. Benyagoub *, A. Audren CIMAP (ex-CIRIL-GANIL), CEA-CNRS-ENSICAEN-Université de Caen Basse Normandie, Bd Henri Becquerel, BP 5133, F-14070 Caen cedex 5, France
a r t i c l e
i n f o
Article history: Available online 21 February 2009 PACS: 61.80.x 61.80.Jh Keywords: Silicon carbide Ion radiation effects Radiation damage Optical defects Optical absorption
a b s t r a c t Silicon carbide (SiC) single crystals were irradiated at room temperature with different ion species of several hundreds MeV in order to explore a wide range of the deposited electronic and nuclear energy losses. The samples were characterized by optical absorption spectroscopy. The comparison of the transmittance data obtained after irradiation with different ion species in combination with the use of energy degraders of different thicknesses allowed to demonstrate that the optical defects created by swift heavy ions are essentially produced by elastic collisions and occur mainly at the end of the ion range region. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction Silicon carbide (SiC) has drawn large interest in the last decades for its various potential technological applications. Due to its wide band gap and its outstanding thermal, electrical and optical properties, SiC is a promising material for high-temperature electronic and optoelectronic devices [1–4]. Moreover, due to its low neutron absorption cross-section and its good mechanical properties and chemical inertness, SiC is also potentially useful for the nuclear industry, either as a cladding material for the nuclear fuel in the future fission reactors or as a protective coating for the first wall in fusion technology [5,6]. Several papers reported on radiation effects induced in SiC by various kinds of energetic particles [7–11]. However, very few studies were devoted to the effects induced by swift heavy ions in this material. The aim of this contribution is to present recent results describing the damage produced in 6H-SiC single crystals by different heavy ions accelerated at several hundreds MeV. Since with such particles the thickness of the bombarded layer extends over a few tens of micrometers, optical absorption spectroscopy in the UV–visible range was chosen for the characterization of the induced damage. This technique is, in fact, well suited for probing thick samples and is also very sensitive for the detection of low defect concentrations. However, it cannot provide the depth distribution of the detected defects. In this study, this drawback
* Corresponding author. Tel.: +33 2 31 45 45 73; fax: +33 2 31 45 47 14. E-mail address: [email protected] (A. Benyagoub). 0168-583X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2009.01.026
was partly overcome by using energy degraders of different thicknesses. 2. Experimental The samples with dimensions of 10 10 mm2 were cut from a single crystalline (0 0 0 1)-oriented 6H-SiC wafer optically polished on both sides and having a thickness of 250 lm. All the samples were partly capped by a 250-lm thick Cu foil in order to preserve virgin areas for calibration. They were irradiated at room temperature with 300-MeV Ni, 910-MeV Xe or 860-MeV Pb ions delivered by the ‘‘Medium Energy Exit” of the GANIL accelerator in Caen (France). The ion range Rp of these ion species is, respectively, 30.9, 48.4 and 33.5 lm. During irradiation, the ion flux was deliberately set below 3 108 ion cm2 s1 in order to prevent target heating. For the irradiations with Xe and Pb ions, some samples were covered by aluminium foils of different thicknesses. The purpose of these aluminium foils (‘energy degraders’) is to decrease the ion energy at the entrance of the SiC specimens and thus to reduce the depth of the bombarded layers. All the samples were characterized after ion irradiation by UV–visible absorption spectroscopy. 3. Results and discussion The transmittance spectra recorded after irradiation with different fluences of Ni, Xe and Pb ions are presented in Fig. 1 together with some spectra registered on the unirradiated part of some samples. The transmittance of the virgin areas is practically zero
1256
A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
the sample irradiated at the fluence U. Eq. (1) provides for each irradiated sample the increase in absorbance caused by the damage produced by the ion irradiation. The transmittance data shown in Fig. 1 were analyzed with Eq. (1), and the obtained values of the increase in absorbance are presented in Fig. 2 with the ion fluence as a parameter. In fact, the different curves of the figure are normalized to the fluence of 1011 ion cm2 in order to facilitate their comparison. This normalization was accomplished by dividing Eq. (1) by the fluence U given in the units of 1011 ion cm2. It appears that for each type of ion irradiation the corresponding curves can almost be merged in a single one. This result indicates that the increase in absorbance is directly proportional to the ion fluence. It also points out that there is no noticeable saturation in the concentration of optically absorbing centers created by ion irradiation, at least in the fluence range explored in this study. One can also notice that the increase in absorbance is all the more pronounced the higher the mass of the irradiating ion indicating that Pb ions induce much more damage than Xe and Ni ions.
Fig. 1. Transmittance spectra recorded on SiC single crystals irradiated at room temperature with different fluences of 300-MeV Ni (a), 910-MeV Xe (b) and 860MeV Pb (c) ions. Some spectra recorded on the unirradiated part of some samples are also shown for comparison.
below the wavelength of 400 nm and then increases abruptly above that wavelength to attain a value around 0.6. This behavior is consistent with similar measurements reported in the literature [12,13]. The small dip appearing around 630 nm very likely originates from the initial nitrogen doping of the as-received SiC wafer [12]. After irradiation, the transmittance decreases all over the wavelength range with increasing ion fluence, whatever the ion species. Also, the absorption edge becomes broader and is shifted towards higher wavelengths due to the generation by the ion irradiation of defect levels located within the band gap. If one neglects the modification brought to the reflectivity by ion bombardment, the change of absorbance in the irradiated material with respect to that of the virgin one is given by:
DAðUÞ ¼ AðUÞ Av irgin ¼ ln
T v irgin ; TðUÞ
ð1Þ
where Avirgin, Tvirgin, A(U) and T(U) are, respectively, the absorbance and the transmittance in the virgin and in the bombarded part of
Fig. 2. Change in absorbance in the SiC samples irradiated at room temperature with different fluences of 300-MeV Ni (a), 910-MeV Xe (b) and 860-MeV Pb (c) ions. The curves are normalized to the fluence of 1011 ion cm2 for the purpose of comparison. This was obtained by dividing their original height (as deduced from Eq. (1)) by the fluence given in the units of 1011 ion cm2 (the normalization factor is indicated between brackets for each curve).
A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
Fig. 3. Similarity of the transmittance curves obtained on SiC samples irradiated with 1013 Ni cm2, 2 1012 Xe cm2 or 1012 Pb cm2.
This effect of the ion mass can also be observed directly by comparing the transmittance curves obtained after irradiation with 1013 Ni cm2, 2 1012 Xe cm2 and 1012 Pb cm2 (see Fig. 3). It is remarkable that these three samples, while irradiated with different ion species at different fluences, exhibit almost the same transmittance indicating that the total amount of optically absorbing centers is the same in these samples. The comparison of the ion fluence necessary to attain this amount of disorder points out that Pb ions are almost two times more efficient than Xe ions and nearly ten times more efficient than Ni ions for creating damage in SiC. It is then interesting to address the origin of this difference. According to the TRIM code [14], the total amount of energy lost in electronic excitations for 300-MeV Ni, 910-MeV Xe and 860-MeV Pb ions is, respectively, 298 MeV, 903 MeV and 846 MeV. Obviously, Xe ions induce much more electronic excitations than Pb ions while they are two times less efficient in creating damage. Therefore, the latter cannot be accounted for by electronic excitations. On the other hand, the total amount of energy lost by nuclear
1257
collisions is about 1.6 MeV for 300-MeV Ni, 7 MeV for 910-MeV Xe and 14 MeV for 860-MeV Pb. These values of the nuclear energy loss scale remarkably well with the efficiency of the corresponding ion species. This result is clear evidence that the optically absorbing centers are essentially created by nuclear collisions. Therefore, their distribution inside the irradiated samples is expected to follow the nuclear energy loss profile. Since the irradiating particles are swift heavy ions, nuclear collisions and thus optically absorbing centers are for the major part distributed deeply inside the samples, in the vicinity of the end of range (i.e. Rp) of the incident ions. In order to check definitely if the optical defects are created near the end of range of the irradiating ions, some SiC samples were covered with aluminium foils acting as energy degraders. In the case of Xe irradiation, two thicknesses were selected: 28 and 42 lm. The first one decreased the incident ion energy down to an average value of 470 MeV at the entrance of the irradiated SiC specimen, reducing then the thickness of the bombarded layer by 21 lm. The second one reduced the ion energy down to 235 MeV and thus decreased the effective thickness of the bombarded layer by 32 lm. Fig. 4 illustrates the evolution with depth of the electronic and nuclear energy losses released by the irradiating Xe ion in these different configurations. In the case of the irradiation without energy degrader, the Xe ion moves across region 1 (21 lm) and region 2 (11 lm) and then stops near the end of region 3 (16 lm). With the use of the 28-lm Al degrader, the ion traverses region 2 and comes at rest near the end of region 3; whereas in the case of the 42-lm Al degrader, the ion travels only in region 3. The transmittance spectra recorded on these samples are presented in Fig. 5 in the case of the irradiation with the fluence of 1012 Xe cm2. The transmittance of a virgin sample is also shown for the purpose of comparison. It clearly appears that the spectra obtained on the irradiated specimens are nearly the same. This result indicates that the change in transmittance is mainly due to the radiation damage occurring in region 3 (i.e. within the end of the ion range region) and that the contribution of region 1 and region 2, where the electronic energy loss is as high as 22 keV nm1, is insignificant. These are evidence that electronic excitations released by swift heavy ions do not create detectable amount of optical defects in SiC. The latter are located predominantly at the end of the ion range region and are thus ascribed essentially to nuclear collisions. Similar results (not shown) were
Fig. 4. Schematic view illustrating the evolution with depth of the electronic and nuclear energy losses released by a 910-MeV Xe ion in SiC with and without the use of energy degraders. The latter are Al foils of 28 and 42 lm.
1258
A. Benyagoub, A. Audren / Nuclear Instruments and Methods in Physics Research B 267 (2009) 1255–1258
defects cannot be accounted for by the huge amount of electronic excitations and ionizations released in the wake of the irradiating ions. Instead, it appears that this disorder is essentially created by nuclear collisions. Both results were confirmed by specific experiments involving energy degraders, which allowed to probe different depths. It is shown that the created optical defects are, for the major part, distributed deeply inside the irradiated samples, i.e. in the vicinity of the end of range region of the incident ions. This result could be of interest for some applications necessitating the modification of the optical properties of SiC deeply below the surface, at any desired depth limited only by the accessible ion energy, with the advantage of not altering shallower regions. Acknowledgements This work was partly supported by the following french research organizations: CPR ISMIR, GdR GEDEPEON and GdR MATINEX. References Fig. 5. Transmittance spectra recorded after irradiation with 910-MeV Xe ions at the same fluence of 1012 Xe cm2 with and without the use of energy degraders. A spectrum registered on a virgin sample is also shown for comparison.
also obtained using energy degraders in the case of the irradiation with 860-MeV Pb ions.
[1] [2] [3] [4] [5] [6] [7]
4. Conclusion The transmittance data obtained on SiC single crystals irradiated with different swift heavy ions indicate that the produced disorder is proportional to the ion fluence for each ion species, suggesting that there is no defect saturation at least in the fluence range explored in this study (i.e. up to 1013 ion cm2). The comparison of these transmittance data points out that the created optical
[8] [9] [10] [11] [12] [13] [14]
J.W. Palmorn, H.S. Kong, R.F. Davies, Appl. Phys. Lett. 51 (1987) 2028. J.A. Edward, K. Das, R.F. Davies, J. Appl. Phys. 63 (1988) 922. K. Shnai, R.S. Scott, B.J. Baliga, IEEE Trans. Electron Dev. ED-36 (1989) 1811. H. Morkoç, S. Strite, G.B. Gao, M.E. Lin, B. Sverdlov, M. Burns, J. Appl. Phys. 76 (1994) 1363. L.H. Ford, N.S. Hibbert, D.G. Martin, J. Nucl. Mater. 45 (1972) 139. P. Fenici, A.J. Rebelo, R.H. Jones, A. Kobyama, L.L. Snead, J. Nucl. Mater. 258 (1998) 215. K. Yasuda, M. Takeda, H. Masuda, A. Yoshida, Phys. Status Solidi (a) 71 (1982) 549. C.J. McHargue, J.M. Williams, Nucl. Instr. and Meth. B 80–81 (1993) 889. E. Wendler, A. Heft, W. Wesch, Nucl. Instr. and Meth. B 141 (1998) 105. W.J. Weber, L.M. Wang, N. Yu, N.J. Hess, Mater. Sci. Eng. A 253 (1998) 62. L.L. Snead, S.J. Zinkle, Nucl. Instr. and Meth. B 191 (2002) 497. E. Wendler, A. Heft, U. Zammit, E. Glaser, M. Marinelli, W. Wesch, Nucl. Instr. and Meth. B 116 (1996) 398. L. Calcagno, M.G. Grimaldi, P. Musumeci, J. Mater. Res. 12 (1997) 1727. J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon, New York, 1985.