- Email: [email protected]
Spectral hole burning study of a neutron-irradiated type IaB natural diamond
Diamond and Related Materials, 3 (1994) 725-727
725
Spectral hole burning study of a neutron-irradiated type IaB natural diamond I. Sildos and A. Osvet Institute of Physics, Estonian Academy of Science, Riia 142, EE2400 Tartu (Estonia)
Abstract Persistent spectral hole burning (SHB) was carried out in several lines in the spectra of the defects created by neutron irradiation of type IaB diamond. The spectral holes in the lines at 655 and 681 n m revealed thermostability up to 200 K. A particular case was a line at 774 nm, where a shift between the positions of the boles, detected in the excitation or the luminescence spectrum, was observed. In this line, SHB can be performed even at room temperature.
1. Introduction
2. Experimental details
Spectral hole burning (SHB) as a kind of high resolution spectroscopy has turned out to be very successful for the investigation of defects and impurities in solids, This method gives not only precise spectroscopic characteristics of defects (by eliminating or reducing the inhomogeneous broadening of spectral lines) but also gives information about the dynamic processes taking place during and after optical excitation of the defects (spectral diffusion, energy relaxation, charge transfer, interaction of the defect with the surrounding matrix) [1]. Many spectroscopic investigations of defects have been carried out in types Ib and Ia diamond, where
In this work, a piece of type IaB natural diamond (linear dimensions of about 3 mm) was prepared by irradiating it with a fast neutron flux of 1019 n cm 2 and subsequent annealing at 950 °C for 30 min. In the experiments, an Ar + -ion laser-pumped linear dye laser or an XeCl-excimer laser-pumped pulse dye laser was used. In our investigations at low temperatures, the absorption and luminescence spectra of the sample were found to contain a number of lines at 594, 644, 649.5, 651.5, 655, 681, 724 and 732 nm (in absorption), and at 649.5, 681, 724, 731, 734, 774 and 813 nm (in luminescence). All the absorption lines were situated on top of quite a strong background, which increased towards the blue end of the spectrum and did not depend on the temperature [11]. The lines at 649.5, 655, 681, 724, 734 and 774 nm could be subjected to selective laser-induced phototransformation, resulting in the appearance of persistent spectral holes in the lines. The most remarkable results were obtained by burning holes in the lines at 649.5 nm, 655 nm and 681 nm, where
defects are created using electron irradiation (see, for example, refs. 2 and 3). In diamond crystals treated in this way, the SHB method has been applied to investigate H4, N-V and GR1 defects [4-7]. A neutron-irradiation treatment has been used to create N-V defects for the SHB measurements [7]; to investigate the optical properties v s . the irradiation dose [8]; to investigate the migration and thermal annealing processes [-9]; to determine the disorder and graphitization from the data of phonon propagation [10]. The purpose of this research was to carry out an SHB study of the photochromic properties of the defects created by neutron-irradiation of type IaB diamond, and to find material for high temperature HB. For this second aspect, the diamond has the advantage that it has an extremely high Debye temperature (1900 K), which enables the detection of informative spectra of defects with well-pronounced zero phonon lines, even at room temperature.
0925-9635/94/$7.00
the holes burnt at 5 K were partially restored by temperature cycling up to 200 K [ 12, 13 ]. In this study, we focused on the line at 774 nm. We performed SHB in spectra at different temperatures. Figure 1 shows the holes burnt in at liquid nitrogen temperature. A shift between the positions of the holes detected in the excitation or the luminescence spectrum was observed (Fig. 2). The width of the hole (0.6 cm-1) in the excitation spectrum is laser-limited but, in the luminescence spectrum, it is much broader (about 2 cm-1). The value of this shift depends on the wavelength of the laser used for burning in the 774 nm line. The measured values are 2.7, 3.8 and 0.6 cm -1 in the
© 1994 - - Elsevier Sequoia. All rights reserved
SSDI 0 9 2 5 - 9 6 3 5 ( 9 3 ) 0 5 0 6 1 - G
I. Sildos, A. Osvet / SHB of neutron-irradiated diamond
726
Z
z .... 765
f .... I .... 770 775 WAVELENGTH, nm
780
Fig. 1. SHB in a neutron-irradiated type IaB diamond, performed at 77 K. Conditions: burning with a linear continuous wave dye laser; spectral half-width of the laser line, 1.1 cm-1; density for burning, 2 W cm 2; duration, 10 rain: (a) luminescence spectrum; excitation at 704 nm; spectral resolution of spectrometer, 0.2 nm; (b) excitation
spectrum;detectionat 840 nm.
A
,%
]
~
,~
B
i
%
i
!'i /~ •
~"
a °J~ ,
773.0
,
,
,
~
773.5
,
,
I
774.0
WAVELENGTH, r t m
.,
A ° ................ 774.0 775.0 WAVELENGTH, m
Fig. 2. Shift between the spectral holes, detected in excitation and luminescence spectra at different temperatures: (a) at 77 K; (b) at 5 K: (a) hole in excitation spectrum; (b) hole in luminescence spectrum (taken with spectral resolution 1 c m - ' ) ; (e) laser line for burning,
case of burning positions at 772.0, 774.0 and 775.5 nm respectively. We also succeeded in burning and detecting spectral holes in the line at 774 nm at room temperature, where the hole width was 1.3 nm (~22 cm-1). 3. Discussion First, we have to admit that the character of the sample prepared by us is rather complicated. In the type IaB diamond, single, pairs and aggregate forms of nitrogen defects are present. It is difficult to estimate, without special investigations, which processes are essential during irradiation and annealing of the crystal, where quite a heavy dose of irradiation was applied, However, disordered carbon regions about 20 A in diameter were found using phonon scattering investigations [10].
For vacancies in electron-irradiated type Ia diamond, the following was concluded. The activation energy for
movement is 2.3 eV, where migration occurs preferentially in the neutral state of the charge. Also, nitrogen aggregates are responsible for the trapping of vacancies in type Ia crystals [2]. Interstitials have been estimated to be mobile at room temperature [14]. Migration of nitrogen atoms and the decomposition of pairs of nitrogen atoms have been estimated to start at 800 K [9]. None of the lines subjected to SHB in our investigation belongs to well-identified defects [15, 16], except the 681 and 724 nm lines mentioned before [8, 9, 17]. It maybe suggested that photochromic defects in our type IaB samples contain nitrogen aggregates in combination with vacancies. A shift in the positions of the holes in our spectra detected in different ways indicates some relaxation of the defect after its optical excitation. If the excited electronic state of the defect appears to be degenerate, then the effect could be explained by the Jahn-Teller distortion of the defect. The dependence of the value of the shift vs. the burning position inside b the e n o nspectral . t r a d i t iline o n a at l ofthe 774nm could explained by a origin inhomogeneous broadening of the line. Indeed, in a sense, the 774 nm line is exceptional in our sample: its spectral width (about 80 cm-1) is about three times larger than that of other lines. One of the possible explanations for this could be the existence of two sources (parameters) for inhomogeneous broadening: one of them is induced by a variety of local strains around the defect [18]; the other source is related to the varying sizes of the disordered regions next to the optical defect. The origin of the disordered regions could be connected with nitrog e n aggregates or carbon bubbles in heavily irradiated diamond.
Acknowledgment This work was supported in part by a Soros Foundation Grant awarded by the American Physical Society.
References
1 W. E. Moerner (ed.), Persistent Spectral Hole Burning: Science and Applications, Springer, Berlin, 1988, p. 60. 2 G. Davies, S. C. Lawson, A. T. Collins, A. Mainwood and s.J. Sharp, Phys. Rev. B, 46 (1992)13157. 3 D. A. Redman, S. Brown, R. H. Sands and S. C. Rand, Phys. Rev. Lett., 67 (1991)3420. 4 R. T. Harley, M. J. Henderson and R. M. Macfarlane, J. Phys. C, 17 (1984) L233. 5 N. R. S. Reddy, N. B. Manson and E. R. Krausz, J. Lumin., 38
(1987) 46.
I. Sildos, A. Osvet / SHB of neutron-irradiated diamond 6 K. Holliday, N. B. Manson, M. Glasbeek and E. van Oort, 3. Phys. Condens. Matter, 1 (1989) 7093. 7 Y. Nishida, Y. Mita, S. Okuda, T. Mihara, R. Kato, M. Ashida, S. Sato, and S. Yazu, in Saito, O. Fukunaga and M. Yoshikawa (eds.), Science and Technology of New Diamond, KTK Scientific, Tokyo, 1990, p. 36. 8 V. G. Vins, A. P. Yelyseev and V. G. Malogobovets, Sverkh. Mater., 4(1988) 18 (in Russian). 9 Y. Nishida, Y. Mita, K. Mori, S. Okuda, S. Sato, S. Yazu, M. Nakagawa and M. Okada, Mater. Sci. Forum, 38-41 (1989) 561. 10 D. T. Morelli and T. A. Perry, in M. Meissner and R. O. Pohl (eds.}, Phonon Scattering in Condensed Matter VII, Springer, Berlin, 1993, p. 37. 11 A. Osvet, A. Suisalu and I. Sildos, Proc. Eston. Acad. Sci. Phys. Math., 41 (1992) 222. 12 I. Sildos, U. Bogner and A. Osvet, in M. Meissner and R. O. Pohl
13
14
15 16 17 18
727
(eds.), Phonon Scattering in Condensed Matter VII, Springer, Berlin, 1993, p. 515. A. Osvet and I. Sildos, in O. Kanert and J.-M. Spaeth (eds.), Proc. X I I Int. Conf. on Defects in Insulating Materials, Schloss Nordkirchen, August, 1992. World Scientific, Singapore, 1993, pp. 373 375. V. S. Vavilov, A. A. Gippius and E. A. Konorova, Electronic and Optical Processes in Diamond. Nauka, Moscow, 1985 (in Russian). F. Bridges, G. Davies, J. Robertson and A. M. Stoneham, J. Phys. Condens. Matter, 2 (1990) 2875. J. E. Field (ed.), The Properties ~f Natural and Synthetic Diamond, Academic Press, London, 1992. M. H. Nazare, M. F. Thomaz, M. Isabel and B. Jorge, Solid State Commun., 55 (1985) 511. A. M. Stoneham, Rev. Mod. Phys., 41 (1969) 82.
725
Spectral hole burning study of a neutron-irradiated type IaB natural diamond I. Sildos and A. Osvet Institute of Physics, Estonian Academy of Science, Riia 142, EE2400 Tartu (Estonia)
Abstract Persistent spectral hole burning (SHB) was carried out in several lines in the spectra of the defects created by neutron irradiation of type IaB diamond. The spectral holes in the lines at 655 and 681 n m revealed thermostability up to 200 K. A particular case was a line at 774 nm, where a shift between the positions of the boles, detected in the excitation or the luminescence spectrum, was observed. In this line, SHB can be performed even at room temperature.
1. Introduction
2. Experimental details
Spectral hole burning (SHB) as a kind of high resolution spectroscopy has turned out to be very successful for the investigation of defects and impurities in solids, This method gives not only precise spectroscopic characteristics of defects (by eliminating or reducing the inhomogeneous broadening of spectral lines) but also gives information about the dynamic processes taking place during and after optical excitation of the defects (spectral diffusion, energy relaxation, charge transfer, interaction of the defect with the surrounding matrix) [1]. Many spectroscopic investigations of defects have been carried out in types Ib and Ia diamond, where
In this work, a piece of type IaB natural diamond (linear dimensions of about 3 mm) was prepared by irradiating it with a fast neutron flux of 1019 n cm 2 and subsequent annealing at 950 °C for 30 min. In the experiments, an Ar + -ion laser-pumped linear dye laser or an XeCl-excimer laser-pumped pulse dye laser was used. In our investigations at low temperatures, the absorption and luminescence spectra of the sample were found to contain a number of lines at 594, 644, 649.5, 651.5, 655, 681, 724 and 732 nm (in absorption), and at 649.5, 681, 724, 731, 734, 774 and 813 nm (in luminescence). All the absorption lines were situated on top of quite a strong background, which increased towards the blue end of the spectrum and did not depend on the temperature [11]. The lines at 649.5, 655, 681, 724, 734 and 774 nm could be subjected to selective laser-induced phototransformation, resulting in the appearance of persistent spectral holes in the lines. The most remarkable results were obtained by burning holes in the lines at 649.5 nm, 655 nm and 681 nm, where
defects are created using electron irradiation (see, for example, refs. 2 and 3). In diamond crystals treated in this way, the SHB method has been applied to investigate H4, N-V and GR1 defects [4-7]. A neutron-irradiation treatment has been used to create N-V defects for the SHB measurements [7]; to investigate the optical properties v s . the irradiation dose [8]; to investigate the migration and thermal annealing processes [-9]; to determine the disorder and graphitization from the data of phonon propagation [10]. The purpose of this research was to carry out an SHB study of the photochromic properties of the defects created by neutron-irradiation of type IaB diamond, and to find material for high temperature HB. For this second aspect, the diamond has the advantage that it has an extremely high Debye temperature (1900 K), which enables the detection of informative spectra of defects with well-pronounced zero phonon lines, even at room temperature.
0925-9635/94/$7.00
the holes burnt at 5 K were partially restored by temperature cycling up to 200 K [ 12, 13 ]. In this study, we focused on the line at 774 nm. We performed SHB in spectra at different temperatures. Figure 1 shows the holes burnt in at liquid nitrogen temperature. A shift between the positions of the holes detected in the excitation or the luminescence spectrum was observed (Fig. 2). The width of the hole (0.6 cm-1) in the excitation spectrum is laser-limited but, in the luminescence spectrum, it is much broader (about 2 cm-1). The value of this shift depends on the wavelength of the laser used for burning in the 774 nm line. The measured values are 2.7, 3.8 and 0.6 cm -1 in the
© 1994 - - Elsevier Sequoia. All rights reserved
SSDI 0 9 2 5 - 9 6 3 5 ( 9 3 ) 0 5 0 6 1 - G
I. Sildos, A. Osvet / SHB of neutron-irradiated diamond
726
Z
z .... 765
f .... I .... 770 775 WAVELENGTH, nm
780
Fig. 1. SHB in a neutron-irradiated type IaB diamond, performed at 77 K. Conditions: burning with a linear continuous wave dye laser; spectral half-width of the laser line, 1.1 cm-1; density for burning, 2 W cm 2; duration, 10 rain: (a) luminescence spectrum; excitation at 704 nm; spectral resolution of spectrometer, 0.2 nm; (b) excitation
spectrum;detectionat 840 nm.
A
,%
]
~
,~
B
i
%
i
!'i /~ •
~"
a °J~ ,
773.0
,
,
,
~
773.5
,
,
I
774.0
WAVELENGTH, r t m
.,
A ° ................ 774.0 775.0 WAVELENGTH, m
Fig. 2. Shift between the spectral holes, detected in excitation and luminescence spectra at different temperatures: (a) at 77 K; (b) at 5 K: (a) hole in excitation spectrum; (b) hole in luminescence spectrum (taken with spectral resolution 1 c m - ' ) ; (e) laser line for burning,
case of burning positions at 772.0, 774.0 and 775.5 nm respectively. We also succeeded in burning and detecting spectral holes in the line at 774 nm at room temperature, where the hole width was 1.3 nm (~22 cm-1). 3. Discussion First, we have to admit that the character of the sample prepared by us is rather complicated. In the type IaB diamond, single, pairs and aggregate forms of nitrogen defects are present. It is difficult to estimate, without special investigations, which processes are essential during irradiation and annealing of the crystal, where quite a heavy dose of irradiation was applied, However, disordered carbon regions about 20 A in diameter were found using phonon scattering investigations [10].
For vacancies in electron-irradiated type Ia diamond, the following was concluded. The activation energy for
movement is 2.3 eV, where migration occurs preferentially in the neutral state of the charge. Also, nitrogen aggregates are responsible for the trapping of vacancies in type Ia crystals [2]. Interstitials have been estimated to be mobile at room temperature [14]. Migration of nitrogen atoms and the decomposition of pairs of nitrogen atoms have been estimated to start at 800 K [9]. None of the lines subjected to SHB in our investigation belongs to well-identified defects [15, 16], except the 681 and 724 nm lines mentioned before [8, 9, 17]. It maybe suggested that photochromic defects in our type IaB samples contain nitrogen aggregates in combination with vacancies. A shift in the positions of the holes in our spectra detected in different ways indicates some relaxation of the defect after its optical excitation. If the excited electronic state of the defect appears to be degenerate, then the effect could be explained by the Jahn-Teller distortion of the defect. The dependence of the value of the shift vs. the burning position inside b the e n o nspectral . t r a d i t iline o n a at l ofthe 774nm could explained by a origin inhomogeneous broadening of the line. Indeed, in a sense, the 774 nm line is exceptional in our sample: its spectral width (about 80 cm-1) is about three times larger than that of other lines. One of the possible explanations for this could be the existence of two sources (parameters) for inhomogeneous broadening: one of them is induced by a variety of local strains around the defect [18]; the other source is related to the varying sizes of the disordered regions next to the optical defect. The origin of the disordered regions could be connected with nitrog e n aggregates or carbon bubbles in heavily irradiated diamond.
Acknowledgment This work was supported in part by a Soros Foundation Grant awarded by the American Physical Society.
References
1 W. E. Moerner (ed.), Persistent Spectral Hole Burning: Science and Applications, Springer, Berlin, 1988, p. 60. 2 G. Davies, S. C. Lawson, A. T. Collins, A. Mainwood and s.J. Sharp, Phys. Rev. B, 46 (1992)13157. 3 D. A. Redman, S. Brown, R. H. Sands and S. C. Rand, Phys. Rev. Lett., 67 (1991)3420. 4 R. T. Harley, M. J. Henderson and R. M. Macfarlane, J. Phys. C, 17 (1984) L233. 5 N. R. S. Reddy, N. B. Manson and E. R. Krausz, J. Lumin., 38
(1987) 46.
I. Sildos, A. Osvet / SHB of neutron-irradiated diamond 6 K. Holliday, N. B. Manson, M. Glasbeek and E. van Oort, 3. Phys. Condens. Matter, 1 (1989) 7093. 7 Y. Nishida, Y. Mita, S. Okuda, T. Mihara, R. Kato, M. Ashida, S. Sato, and S. Yazu, in Saito, O. Fukunaga and M. Yoshikawa (eds.), Science and Technology of New Diamond, KTK Scientific, Tokyo, 1990, p. 36. 8 V. G. Vins, A. P. Yelyseev and V. G. Malogobovets, Sverkh. Mater., 4(1988) 18 (in Russian). 9 Y. Nishida, Y. Mita, K. Mori, S. Okuda, S. Sato, S. Yazu, M. Nakagawa and M. Okada, Mater. Sci. Forum, 38-41 (1989) 561. 10 D. T. Morelli and T. A. Perry, in M. Meissner and R. O. Pohl (eds.}, Phonon Scattering in Condensed Matter VII, Springer, Berlin, 1993, p. 37. 11 A. Osvet, A. Suisalu and I. Sildos, Proc. Eston. Acad. Sci. Phys. Math., 41 (1992) 222. 12 I. Sildos, U. Bogner and A. Osvet, in M. Meissner and R. O. Pohl
13
14
15 16 17 18
727
(eds.), Phonon Scattering in Condensed Matter VII, Springer, Berlin, 1993, p. 515. A. Osvet and I. Sildos, in O. Kanert and J.-M. Spaeth (eds.), Proc. X I I Int. Conf. on Defects in Insulating Materials, Schloss Nordkirchen, August, 1992. World Scientific, Singapore, 1993, pp. 373 375. V. S. Vavilov, A. A. Gippius and E. A. Konorova, Electronic and Optical Processes in Diamond. Nauka, Moscow, 1985 (in Russian). F. Bridges, G. Davies, J. Robertson and A. M. Stoneham, J. Phys. Condens. Matter, 2 (1990) 2875. J. E. Field (ed.), The Properties ~f Natural and Synthetic Diamond, Academic Press, London, 1992. M. H. Nazare, M. F. Thomaz, M. Isabel and B. Jorge, Solid State Commun., 55 (1985) 511. A. M. Stoneham, Rev. Mod. Phys., 41 (1969) 82.