- Email: [email protected]
Photoluminescence character of Xe ion irradiated sapphire
Available online at www.sciencedirect.com
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 266 (2008) 2998–3001 www.elsevier.com/locate/nimb
Photoluminescence character of Xe ion irradiated sapphire q Song Yin a,b,*, Xie Er-qing b, Zhang Chong-hong a, Wang Zhi-guang a, Zhou Li-hong a, Ma Yi-Zhong a, Yao Cun-feng a, Zang Hang a, Liu Chun-bao a, Sheng Yan-bin a, Gou Jie a a
Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Road, Lanzhou 730000, China b School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China Available online 31 March 2008
Abstract In the present work the photoluminescence (PL) character of sapphire implanted with 180 keV Xe and irradiated with 308 MeV Xe ions was studied. The virgin, implanted and irradiated samples were investigated by PL and Fourier transform infrared (FTIR) spectra measurements. The obtained PL spectra showed the maximum emission bands at 2.75, 3.0 and 3.26 eV for the implanted fluence of 1.0 1015 ions/cm2 and at 2.4 and 3.47 eV for the irradiated fluence of 1.0 1013 ions/cm2. The FTIR spectra showed a broaden absorption band between 460 and 630 cm1, indicating that strong damaged region formed in Al2O3. Ó 2008 Elsevier B.V. All rights reserved. Keywords: Ion implantation; Ion irradiation; Al2O3; PL spectra
1. Introduction Sapphire is a wide band gap optical material with its broad transmission spectrum from ultraviolet to visible and near-infrared (0.2–2 lm). It can be applied in the field of optics and fusion reactors as an insulator, and as the optical window [1]. The ability of Al2O3 for application in optical systems of radiation facilities depends strongly on the occurrence of radiation induced optical absorption or color centers. The defect centers induced by electron, neutron and ion irradiation in sapphire are mainly F centers (oxygen vacancy with two electrons), F+ center (oxygen vacancy with one electron), F2 centers (two oxygen vacancies with four electrons), Fþ 2 centers (two oxygen vacancies with three electrons) and F2þ 2 centers (two oxygen vacancies with two electrons) [2–4]. Ion irradiation can in a
controlled induce changes in microstructure of materials and this can helps to illuminate structure evolution induced by irradiation. Alumina exhibits many exciting physicochemical properties for industrial applications. High energy heavy ion interacting with material loses its energy through electronic processes and nuclear processes. Point defects, defects clusters and/or ion tracks can be created in the irradiated materials along the range and the defect structure depends on the energy loss values and irradiated fluences. In the process of using them as optical and electrical materials, in some cases, the material response to radiation is much concerned. Color centers can also be produced by electron, neutron and ion irradiations [5]. In the present work the photoluminescence character of single crystal sapphire (Al2O3) irradiated by 180 keV Xe ions to the fluences ranging from 1 1014 to 1 1016 ions/cm2 or by 308 MeV Xe ions to the fluences ranging from 1 1012 to 1 1013 ions/cm2 was studied.
q
Foundation items: National Natural Science Foundation of China (10705037, 10575124), Natural Science foundation of Gansu (3ZS051A25-053) and director foundation of Institute of Modern Physics. * Corresponding author. Address: Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Road, Lanzhou 730000, China. Tel.: +86 931 4969633; fax: +86 931 4969201. E-mail address: [email protected] (S. Yin). 0168-583X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2008.03.210
2. Experimental details High purity Al2O3 single crystals with polished surfaces were implanted with 180 keV and irradiated with 308 MeV Xe ions. According to the Monte Carlo code SRIM 2006
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001 2
10
1
Energy loss [keV/nm]
calculation, the projected range of 308 MeV Xe beam in Al2O3 is about 16.26 lm. For 180 keV Xe ions the corresponding values are around 45.7 nm depending on incident ions energy. The ion implantation experiments were performed at the 320 kV high voltage platform (IMP, Lanzhou) and Xe ion irradiation was carried out at the HIRFL-SFC facility in Lanzhou. Details of the implantation or irradiation parameters are given in Table 1. Flux was controlled below 5 108 ions/s/cm2 to avoid heating of samples and the fluence was continuously monitored during irradiation. The energy loss values and the range of the irradiated ions in the material were calculated by SRIM 2006 code. The samples were investigated by Fourier transform infrared (FTIR) and fluorescence spectroscopes (Spectrum GX of Perkin–Elmer and RF-5301PC of SHIMADZU). The PL spectra were obtained using 3.64 eV and 4.0 eV excitation light.
2999
10
0
10
-1
10
-2
10
0
2
4 6 8 10 12 14 Distance from sample surface [micron]
16
18
Fig. 1. Electron energy loss (dot lines) and nuclear energy loss (solid lines) values along the projected ranges of 308 MeV Xe ions. SRIM 2006 calculation.
3. Results 800
Table 1 Implantation and irradiation parameters No. 0# 1# 2# 3# 4# 5# 6#
Ion
E (MeV)
2
Fluence (ions/cm )
T (K)
700
Intensity (a.u.)
600 500
3#
400 300 200
1#
100
2 0
0 2.0
#
#
2.5
3.0
3.5
Energy (eV)
Fig. 2. PL spectra of Xe ion irradiatied sapphire.
350
3# 300 250 Intensity (a.u.)
The threshold value of electronic stopping power (Se) from 42.7 keV/nm to 63 keV/nm for producing latent ion tracks in sapphire has been reported [6] to be very high, it related with the ion or cluster velocity. Extended defects can be induced by electronic stopping processes at Se values above 20 keV/nm [7]. As shown in Fig. 1 for 308 MeV Xe ion irradiations, the maximum values of the electronic stopping power can achieve 28.3 keV/nm. Therefore point defects and small defect clusters in irradiated samples are mainly induced by electronic stopping processes. In Fig. 2, PL peaks located at 2.4 eV and 3.47 eV were appeared in 308 MeV Xe ions irradiated samples, the intensity of emission band become more and more strong with increasing Xe ion irradiation fluence, and it achieves a maximum value at 1 1013 ions/cm2 irradiated samples. In Fig. 4, the PL peaks were appeared at 2.75 eV and 3.0 eV in samples implanted with 180 keV Xe ions. Fig. 3 is the excitation spectra of samples irradiated with 308 MeV Xe ions and implanted with 180 keV Xe ions. It was found that the most efficient excitation light is that with a wavelength at about 4.0 eV and 3.64 eV, respectively. Fig. 5 shows the FTIR spectra of sapphire irradiated with 308-MeV Xe ions. Two absorption bands at 485– 515 and 630 cm1 were observed. After Xe ion irradiating,
200 150
5# 2#
100
1#
6#
Xe Xe Xe Xe Xe Xe
308 308 308 0.180 0.180 0.180
0# is a virgin sapphire sample.
12
1.0 10 5.0 1012 1.0 1013 1.0 1014 1.0 1015 1.0 1016
320 320 320 320 320 320
50
0
#
4# 0 3.2
3.4
3.6
3.8 4.0 Energy (eV)
4.2
4.4
4.6
Fig. 3. Excitation spectra of different Al2O3 samples. The sample conditions are given in Table 1.
3000
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001 120
5
100
#
80
2.0
40
Absorbance(a.u.)
# 0
60 Intensity (a.u.)
630
2.5
a
# 6 # 4
20 120 100
#
5
b c
80
1.5
3
#
1.0
# 2 # 1
0.5
60
b 40
d
20 0 2.0
0
0.0 400
a
600
#
800
1000
1200
1400
Wavenumber (cm-1 ) 2.5
3.0
3.5
Fig. 5. FTIR spectra of different Al2O3 samples. The sample conditions are given in Table 1.
Energy (eV)
Fig. 4. PL spectra of virgin and Xe ion implanted sapphire (a) and the deconvolution of the PL spectra of Xe ions implanted (5#) Al2O3 sample (b).
the flat-band diagram of Al2O3 summarizing the relative energy positions of single (F-type) and paired (F2-type) anion vacancies of different charge states. The p-like excited state split by the crystal field into three states labeled 1B, 2A and 2B. According to fig. 6, the PL band at 2.75 eV and 3.47 eV should be from latent excitation þ luminescences (F2þ 2 colour center transition c and (F2 colour center transition e), whereas the PL peaks at 2.4 eV, 3.0 eV and 3.26 eV are due to recombination luminescences (Fig. 6 transitions f, b and a). From the literatures [10–13] it was known that nano-sized gas bubbles could form in Al2O3 after implantation with inert gas ions in the temperature range between 600 K and 1250 K. The formation of nano-sized gas bubbles may enhance the PL intensity [14,16]. Concerning to the defects production mechanisms, up to now, there are still discrepancies on which processes
the absorption band was broadened with increasing Xe ion irradiation fluence, indicated that Al2O3 matrix was destroyed. It implies that point defects, defects clusters may occur in the Xe doped region. 4. Discussion Gourary and Adrian [8] proposed different F-type colour centers in Al2O3, and La, Bartram and Cox [9] calculated pseudo wavefunctions including contributions from s-, p- and d-electronic functions based on the anisotropic crystal field potentials. The trapped charge was well localized within a shell of radius equal to the average distance of the nearest neighboring cations about 1.92A. Fig. 6 shows
Conduction band 1P*
2B
1P
2A
2P*
1B
3P 6.05eV
Ec
2.4eV
3.0eV
2P
f
44.09eV
3.47eV
a 2.2eV
e 3.26eV
b 3.8eV
3S*
2.75eV
c Eg
1S*
F2
1S
F2
9eV
F2 2
1A F
F+
Ev
Valence band Fig. 6. Flat-band diagram of Al2O3 summarizing the relative energy positions of single (F-type) and paired (F2-type) anion vacancies of different charge states.
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001
are the dominating one in producing color centers. Canut believe that the major part of color centers are created by elastic collisions, i.e. the nuclear processes are the dominant factors for producing defects in single crystal aAl2O3 [7]. However, Mohanty have concluded that the electron energy loss processes are the dominant factors for producing color centers in a-Al2O3 [15]. The FTIR absorption band at 981–1148 cm1 is due to the flex vibrations of Al– O–Al. The variation patterns of FTIR absorption band at 485–515 cm1 and 630 cm1 are from the matrix vibration of Al2O3 indicating that Al2O3 matrix was destroyed, it implies that point defects, defects clusters may occur in the Xe atom doped region. Therefore, ion irradiation is expected to enhance the recombination efficiency of deep defect center in the energy gap and thus luminescence shifting towards to blue light. Damage creation and composition segregation could also result in the enhancement of the PL intensity of Xe ion irradiated Al2O3. 5. Conclusions Single crystalline Al2O3 samples were irradiated with 180 keV and 308 MeV Xe ions to various fluences and the radiation induced color centers were investigated by PL spectra measurements. The obtained results suggest that an intense blue-violet PL band centred at about 2.75–3.26 eV was formed in all samples implanted with 180 keV Xe ions. In all cases the intensity arrived at maximum at the fluence of 1 1015 ions/cm2. After 308 MeV Xe ions irradiation, PL centers appeared at about 2.4 eV and 3.47 eV, and getting increases with increasing Xe irradiation fluences.
3001
Acknowledgement We are grateful to Dr. Jinyu Li (IMP, Lanzhou) for ions implantations and to the operation staff of HIRFL for help during the irradiation experiments. References [1] J. Garcia-Guinea, J. Rubio, V. Correcher, F.J. Valle-Fuentes, Radiat. Meas. 33 (2001) 653. [2] K.S. Jheeta, D.C. Jain, Ravi Kumar, et al., Nucl. Instr. and Meth. B 353 (2006) 190. [3] K.P.D. Lagerlo¨f, R.W. Grimes, Acta Mater. 46 (16) (1998) 5689. [4] Y. Chen, M.M. Abraham, D.F. Pedraza, Nucl. Instr. and Meth. B 59/ 60 (1991) 1163. [5] B.D. Evans, J. Nucl. Mater. 219 (1995) 202. [6] V.A. Skuratov, S.J. Zinkle, A.E. Efimov, et al., Nucl. Instr. and Meth. B 203 (2003) 136. [7] B. Canut, A. Benyagoub, G. Marest, et al., Phys. Rev. B 51 (1995) 12194. [8] B.S. Gourary, F.J. Adrian, Solid State Phys. 10 (1960) 127. [9] S.Y. La, R.H. Bartram, R.T. Cox, J. Phys. Chem. Solids 34 (1973) 1079. [10] Bruce D. Evans, J. Nucl. Mater. 219 (1995) 202. [11] Yin Song, Yunfan Jin, Zhiguang Wang, et al., High Energ. Phys. Nucl. Phys. 28 (2004) 626. [12] M.A. van Huis, A. van Veen, F. Labohm, et al., Nucl. Instr. and Meth. B 216 (2004) 149. [13] Chonghong Zhang, Keqin Chen, Yinshu Wang, Acta Phys. Sin. 46 (1997) 1774. [14] Yin Song, Chonghong Zhang, Zhiguang Wang, et al., Nucl. Instr. and Meth. B 245 (2006) 210. [15] T. Mohanty, N.C. Mishra, F. Singh, et al., Radiat. Meas. 36 (2003) 723. [16] Yin Song, Zhiguang Wang, Kongfang Wei, et al., Acta Phys. Sin. 56 (1) (2007) 551.
NIM B Beam Interactions with Materials & Atoms
Nuclear Instruments and Methods in Physics Research B 266 (2008) 2998–3001 www.elsevier.com/locate/nimb
Photoluminescence character of Xe ion irradiated sapphire q Song Yin a,b,*, Xie Er-qing b, Zhang Chong-hong a, Wang Zhi-guang a, Zhou Li-hong a, Ma Yi-Zhong a, Yao Cun-feng a, Zang Hang a, Liu Chun-bao a, Sheng Yan-bin a, Gou Jie a a
Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Road, Lanzhou 730000, China b School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China Available online 31 March 2008
Abstract In the present work the photoluminescence (PL) character of sapphire implanted with 180 keV Xe and irradiated with 308 MeV Xe ions was studied. The virgin, implanted and irradiated samples were investigated by PL and Fourier transform infrared (FTIR) spectra measurements. The obtained PL spectra showed the maximum emission bands at 2.75, 3.0 and 3.26 eV for the implanted fluence of 1.0 1015 ions/cm2 and at 2.4 and 3.47 eV for the irradiated fluence of 1.0 1013 ions/cm2. The FTIR spectra showed a broaden absorption band between 460 and 630 cm1, indicating that strong damaged region formed in Al2O3. Ó 2008 Elsevier B.V. All rights reserved. Keywords: Ion implantation; Ion irradiation; Al2O3; PL spectra
1. Introduction Sapphire is a wide band gap optical material with its broad transmission spectrum from ultraviolet to visible and near-infrared (0.2–2 lm). It can be applied in the field of optics and fusion reactors as an insulator, and as the optical window [1]. The ability of Al2O3 for application in optical systems of radiation facilities depends strongly on the occurrence of radiation induced optical absorption or color centers. The defect centers induced by electron, neutron and ion irradiation in sapphire are mainly F centers (oxygen vacancy with two electrons), F+ center (oxygen vacancy with one electron), F2 centers (two oxygen vacancies with four electrons), Fþ 2 centers (two oxygen vacancies with three electrons) and F2þ 2 centers (two oxygen vacancies with two electrons) [2–4]. Ion irradiation can in a
controlled induce changes in microstructure of materials and this can helps to illuminate structure evolution induced by irradiation. Alumina exhibits many exciting physicochemical properties for industrial applications. High energy heavy ion interacting with material loses its energy through electronic processes and nuclear processes. Point defects, defects clusters and/or ion tracks can be created in the irradiated materials along the range and the defect structure depends on the energy loss values and irradiated fluences. In the process of using them as optical and electrical materials, in some cases, the material response to radiation is much concerned. Color centers can also be produced by electron, neutron and ion irradiations [5]. In the present work the photoluminescence character of single crystal sapphire (Al2O3) irradiated by 180 keV Xe ions to the fluences ranging from 1 1014 to 1 1016 ions/cm2 or by 308 MeV Xe ions to the fluences ranging from 1 1012 to 1 1013 ions/cm2 was studied.
q
Foundation items: National Natural Science Foundation of China (10705037, 10575124), Natural Science foundation of Gansu (3ZS051A25-053) and director foundation of Institute of Modern Physics. * Corresponding author. Address: Institute of Modern Physics, Chinese Academy of Sciences, No. 509 Nanchang Road, Lanzhou 730000, China. Tel.: +86 931 4969633; fax: +86 931 4969201. E-mail address: [email protected] (S. Yin). 0168-583X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2008.03.210
2. Experimental details High purity Al2O3 single crystals with polished surfaces were implanted with 180 keV and irradiated with 308 MeV Xe ions. According to the Monte Carlo code SRIM 2006
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001 2
10
1
Energy loss [keV/nm]
calculation, the projected range of 308 MeV Xe beam in Al2O3 is about 16.26 lm. For 180 keV Xe ions the corresponding values are around 45.7 nm depending on incident ions energy. The ion implantation experiments were performed at the 320 kV high voltage platform (IMP, Lanzhou) and Xe ion irradiation was carried out at the HIRFL-SFC facility in Lanzhou. Details of the implantation or irradiation parameters are given in Table 1. Flux was controlled below 5 108 ions/s/cm2 to avoid heating of samples and the fluence was continuously monitored during irradiation. The energy loss values and the range of the irradiated ions in the material were calculated by SRIM 2006 code. The samples were investigated by Fourier transform infrared (FTIR) and fluorescence spectroscopes (Spectrum GX of Perkin–Elmer and RF-5301PC of SHIMADZU). The PL spectra were obtained using 3.64 eV and 4.0 eV excitation light.
2999
10
0
10
-1
10
-2
10
0
2
4 6 8 10 12 14 Distance from sample surface [micron]
16
18
Fig. 1. Electron energy loss (dot lines) and nuclear energy loss (solid lines) values along the projected ranges of 308 MeV Xe ions. SRIM 2006 calculation.
3. Results 800
Table 1 Implantation and irradiation parameters No. 0# 1# 2# 3# 4# 5# 6#
Ion
E (MeV)
2
Fluence (ions/cm )
T (K)
700
Intensity (a.u.)
600 500
3#
400 300 200
1#
100
2 0
0 2.0
#
#
2.5
3.0
3.5
Energy (eV)
Fig. 2. PL spectra of Xe ion irradiatied sapphire.
350
3# 300 250 Intensity (a.u.)
The threshold value of electronic stopping power (Se) from 42.7 keV/nm to 63 keV/nm for producing latent ion tracks in sapphire has been reported [6] to be very high, it related with the ion or cluster velocity. Extended defects can be induced by electronic stopping processes at Se values above 20 keV/nm [7]. As shown in Fig. 1 for 308 MeV Xe ion irradiations, the maximum values of the electronic stopping power can achieve 28.3 keV/nm. Therefore point defects and small defect clusters in irradiated samples are mainly induced by electronic stopping processes. In Fig. 2, PL peaks located at 2.4 eV and 3.47 eV were appeared in 308 MeV Xe ions irradiated samples, the intensity of emission band become more and more strong with increasing Xe ion irradiation fluence, and it achieves a maximum value at 1 1013 ions/cm2 irradiated samples. In Fig. 4, the PL peaks were appeared at 2.75 eV and 3.0 eV in samples implanted with 180 keV Xe ions. Fig. 3 is the excitation spectra of samples irradiated with 308 MeV Xe ions and implanted with 180 keV Xe ions. It was found that the most efficient excitation light is that with a wavelength at about 4.0 eV and 3.64 eV, respectively. Fig. 5 shows the FTIR spectra of sapphire irradiated with 308-MeV Xe ions. Two absorption bands at 485– 515 and 630 cm1 were observed. After Xe ion irradiating,
200 150
5# 2#
100
1#
6#
Xe Xe Xe Xe Xe Xe
308 308 308 0.180 0.180 0.180
0# is a virgin sapphire sample.
12
1.0 10 5.0 1012 1.0 1013 1.0 1014 1.0 1015 1.0 1016
320 320 320 320 320 320
50
0
#
4# 0 3.2
3.4
3.6
3.8 4.0 Energy (eV)
4.2
4.4
4.6
Fig. 3. Excitation spectra of different Al2O3 samples. The sample conditions are given in Table 1.
3000
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001 120
5
100
#
80
2.0
40
Absorbance(a.u.)
# 0
60 Intensity (a.u.)
630
2.5
a
# 6 # 4
20 120 100
#
5
b c
80
1.5
3
#
1.0
# 2 # 1
0.5
60
b 40
d
20 0 2.0
0
0.0 400
a
600
#
800
1000
1200
1400
Wavenumber (cm-1 ) 2.5
3.0
3.5
Fig. 5. FTIR spectra of different Al2O3 samples. The sample conditions are given in Table 1.
Energy (eV)
Fig. 4. PL spectra of virgin and Xe ion implanted sapphire (a) and the deconvolution of the PL spectra of Xe ions implanted (5#) Al2O3 sample (b).
the flat-band diagram of Al2O3 summarizing the relative energy positions of single (F-type) and paired (F2-type) anion vacancies of different charge states. The p-like excited state split by the crystal field into three states labeled 1B, 2A and 2B. According to fig. 6, the PL band at 2.75 eV and 3.47 eV should be from latent excitation þ luminescences (F2þ 2 colour center transition c and (F2 colour center transition e), whereas the PL peaks at 2.4 eV, 3.0 eV and 3.26 eV are due to recombination luminescences (Fig. 6 transitions f, b and a). From the literatures [10–13] it was known that nano-sized gas bubbles could form in Al2O3 after implantation with inert gas ions in the temperature range between 600 K and 1250 K. The formation of nano-sized gas bubbles may enhance the PL intensity [14,16]. Concerning to the defects production mechanisms, up to now, there are still discrepancies on which processes
the absorption band was broadened with increasing Xe ion irradiation fluence, indicated that Al2O3 matrix was destroyed. It implies that point defects, defects clusters may occur in the Xe doped region. 4. Discussion Gourary and Adrian [8] proposed different F-type colour centers in Al2O3, and La, Bartram and Cox [9] calculated pseudo wavefunctions including contributions from s-, p- and d-electronic functions based on the anisotropic crystal field potentials. The trapped charge was well localized within a shell of radius equal to the average distance of the nearest neighboring cations about 1.92A. Fig. 6 shows
Conduction band 1P*
2B
1P
2A
2P*
1B
3P 6.05eV
Ec
2.4eV
3.0eV
2P
f
44.09eV
3.47eV
a 2.2eV
e 3.26eV
b 3.8eV
3S*
2.75eV
c Eg
1S*
F2
1S
F2
9eV
F2 2
1A F
F+
Ev
Valence band Fig. 6. Flat-band diagram of Al2O3 summarizing the relative energy positions of single (F-type) and paired (F2-type) anion vacancies of different charge states.
S. Yin et al. / Nucl. Instr. and Meth. in Phys. Res. B 266 (2008) 2998–3001
are the dominating one in producing color centers. Canut believe that the major part of color centers are created by elastic collisions, i.e. the nuclear processes are the dominant factors for producing defects in single crystal aAl2O3 [7]. However, Mohanty have concluded that the electron energy loss processes are the dominant factors for producing color centers in a-Al2O3 [15]. The FTIR absorption band at 981–1148 cm1 is due to the flex vibrations of Al– O–Al. The variation patterns of FTIR absorption band at 485–515 cm1 and 630 cm1 are from the matrix vibration of Al2O3 indicating that Al2O3 matrix was destroyed, it implies that point defects, defects clusters may occur in the Xe atom doped region. Therefore, ion irradiation is expected to enhance the recombination efficiency of deep defect center in the energy gap and thus luminescence shifting towards to blue light. Damage creation and composition segregation could also result in the enhancement of the PL intensity of Xe ion irradiated Al2O3. 5. Conclusions Single crystalline Al2O3 samples were irradiated with 180 keV and 308 MeV Xe ions to various fluences and the radiation induced color centers were investigated by PL spectra measurements. The obtained results suggest that an intense blue-violet PL band centred at about 2.75–3.26 eV was formed in all samples implanted with 180 keV Xe ions. In all cases the intensity arrived at maximum at the fluence of 1 1015 ions/cm2. After 308 MeV Xe ions irradiation, PL centers appeared at about 2.4 eV and 3.47 eV, and getting increases with increasing Xe irradiation fluences.
3001
Acknowledgement We are grateful to Dr. Jinyu Li (IMP, Lanzhou) for ions implantations and to the operation staff of HIRFL for help during the irradiation experiments. References [1] J. Garcia-Guinea, J. Rubio, V. Correcher, F.J. Valle-Fuentes, Radiat. Meas. 33 (2001) 653. [2] K.S. Jheeta, D.C. Jain, Ravi Kumar, et al., Nucl. Instr. and Meth. B 353 (2006) 190. [3] K.P.D. Lagerlo¨f, R.W. Grimes, Acta Mater. 46 (16) (1998) 5689. [4] Y. Chen, M.M. Abraham, D.F. Pedraza, Nucl. Instr. and Meth. B 59/ 60 (1991) 1163. [5] B.D. Evans, J. Nucl. Mater. 219 (1995) 202. [6] V.A. Skuratov, S.J. Zinkle, A.E. Efimov, et al., Nucl. Instr. and Meth. B 203 (2003) 136. [7] B. Canut, A. Benyagoub, G. Marest, et al., Phys. Rev. B 51 (1995) 12194. [8] B.S. Gourary, F.J. Adrian, Solid State Phys. 10 (1960) 127. [9] S.Y. La, R.H. Bartram, R.T. Cox, J. Phys. Chem. Solids 34 (1973) 1079. [10] Bruce D. Evans, J. Nucl. Mater. 219 (1995) 202. [11] Yin Song, Yunfan Jin, Zhiguang Wang, et al., High Energ. Phys. Nucl. Phys. 28 (2004) 626. [12] M.A. van Huis, A. van Veen, F. Labohm, et al., Nucl. Instr. and Meth. B 216 (2004) 149. [13] Chonghong Zhang, Keqin Chen, Yinshu Wang, Acta Phys. Sin. 46 (1997) 1774. [14] Yin Song, Chonghong Zhang, Zhiguang Wang, et al., Nucl. Instr. and Meth. B 245 (2006) 210. [15] T. Mohanty, N.C. Mishra, F. Singh, et al., Radiat. Meas. 36 (2003) 723. [16] Yin Song, Zhiguang Wang, Kongfang Wei, et al., Acta Phys. Sin. 56 (1) (2007) 551.