- Email: [email protected]
Effect of rapid thermal treatment on photoluminescence of surface passivated porous silicon
ARTICLE IN PRESS
Journal of Luminescence 128 (2008) 317–320 www.elsevier.com/locate/jlumin
Effect of rapid thermal treatment on photoluminescence of surface passivated porous silicon Yue Zhaoa,b,, Dongsheng Lib, Shuoxiang Xingc, Wenbin Sanga, Deren Yangb, Minhua Jiangb,d a
Department of Electronic Information Materials, Shanghai University, Shanghai 200072, China b State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China c Clean Energy and Environment Engineering Key Laboratory of Ministry of Education, Zhejiang University, Hangzhou 310027, China d State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, PR China Received 4 June 2005; received in revised form 9 April 2007; accepted 9 April 2007 Available online 6 August 2007
Abstract The photoluminescence of porous silicon with and without carbon deposition fabricated by plasma-enhanced chemical vapor deposition technique has been investigated. After the deposition, the rapid thermal processes in the temperature ranging from 500 to 1100 1C have been carried out. It was found that after the carbon deposition a new intense blue emission appeared. The rapid thermal processes at 800and 900 1C could enhance the blue emission, while the other rapid thermal processes quenched it. Finally, the mechanism for the effect of carbon deposition and rapid thermal processes on photoluminescence properties of porous silicon was discussed. r 2007 Elsevier B.V. All rights reserved. Keywords: Porous silicon; Blue emission; Rapid thermal processes
1. Introduction After the photoluminescence (PL) of electrochemically etched porous silicon (Por-Si) was reported in 1990 [1], it has become an attractive material in the field of electronics and opto-electronics. However, the large amounts of highly reactive internal surface of Por-Si compared with bulk Si increase drastically its sensitivity to air. To overcome the degradation of PL intensity with time, post-treatment processes, such as rapid thermal oxidation [2–6], rapid thermal processes (RTPs) under NH3 or N2 atmosphere [7–9], high-and low-temperature processes under different atmospheres [10–13], are used to passivate Por-Si. These post-treatment processes greatly enhance and stabilize the PL of Por-Si. In addition, silicon–carbon bonds can be also used to passivate the surface of Por-Si, Corresponding author. State Key Laboratory of Silicon Materials, Zhejiang University, Zheda Road 38, Hangzhou 310027, China, Tel.: +86 571 87951667; fax: +86 571 87952322. E-mail address: [email protected] (Y. Zhao).
0022-2313/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2007.04.015
because the bonds protect from the oxidation of the Por-Si surface. Several groups have investigated the formation of silicon–carbon bonds on Por-Si by means of different techniques including the two-step wet chemical technique [14,15], magnetron controlled sputtering [16], capacitive RF discharge plasma deposition [17], ionized cluster beam deposition [18], chemical vapor deposition [19], hot filament chemical vapor deposition [20] and thermally carbonized process [21,22]. The carbonized Por-Si has been observed to be stable in various chemical environments. These results also showed that the structure of carbonized Por-Si has the stable and efficient luminescence in visible spectral range. In this paper, we investigated the luminescence of Por-Si carbonized by plasma enhancement chemical vapor deposition (PECVD) method. In PECVD process, the deposited film can be produced in a very large area and at low temperature, which is beneficial for device fabrication. After the deposited processes, rapid thermal processes (RTPs) that are now widely employed in the microelectronic industry were used as the post-treatments.
ARTICLE IN PRESS 318
Y. Zhao et al. / Journal of Luminescence 128 (2008) 317–320
2. Experiments 2
3. Results and discussions Fig. 1 (a) depicts the PL spectra of the as prepared and the carbonized Por-Si. The corresponding FTIR spectra of the two types of samples are shown in Fig. 1(b). A PL peak centered at 570 nm is observed in the as-prepared Por-Si samples (Fig. 1. a (1)). After the deposition of C film on the Por-Si surface, a new blue band centered at about 450 nm (Fig. 1. a (2)) and the peak at 570 nm increases slightly. Compared with the as-prepared PS, the Si–O–Si related FTIR vibration bands at 1084 cm 1 and 463 cm 1 are largely strengthened in the carbonized Por-Si (Fig. 1b). This means that during the C deposition, the PS was oxidized. The SEM images of the surface structure of the asprepared and carbonized Por-Si samples are shown in Fig. 2. The two samples have the same columnar structure. It can be seen from Fig. 2 that after the C deposition the fine structure of the as-prepared sample was lost, and a thick film was formed on the surface, resulting in the generation of C–Si bonds. In Fig. 2(b), the inset image is the energy dispersive spectral of the carbonized sample. The weak C peak is shown in this picture, which indicated that the C atoms were attached on the surface of the carbonized samples and may affect the PL property of this sample.
Intensity(a.u.)
60 40 20 1
0 400
500 600 Wavelength(nm)
700
1084
4
920
2
463
3
610
Absorptance(a.u.)
(1 0 0)-oriented and boron-doped polished single crystal Si wafers with a resistivity of 10-20 O cm were used to prepare Por-Si samples. The anodization was conducted in a solution of HF:C2H5OH=1:2 at room temperature. The constant current density was 50 mA/cm2 and the etched time was 60 min. Before being etched, the back of the wafers was deposited with Al by thermal evaporation to provide an ohmic contact. After the fabrication of Por-Si, the samples were rinsed with de-ionized water and dried in air. Then, the backside Al film was removed with aqueous HF. The C films were deposited by the PECVD method. The source gas was C2H2 and the substrate temperature was 1601C. The C2H2 flow rate was 20 sccm. The deposition pressure was kept at 6 Pa and the power was at 30 W. After the deposition, the RTPs were carried out for 30 s in the temperature ranging from 500 to 1100 1C in Ar atmosphere. The Ar flux was about 1.5 L/min. The heating rate and the cooling rate were about 50 1C/s. The samples were characterized by PL spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The PL spectra excited by a Xe lamp at 360 nm wavelength were measured with a HITACHI F-4500 fluorescence spectrophotometer. The infrared absorption spectra were taken by using a Bruker IFS 66v/S FTIR spectroscope. The appearance observations were carried out by JSM-5610LV SEM. All the measurements were carried out at room temperature.
2 1
1
500
1000
1500
2000
Wavenumber(cm-1)
Fig. 1. PL spectra (a) and FTIR spectra (b) of the samples. (1) asprepared Por-Si samples; (2) the samples deposited with carbon.
The PL of Por-Si has been considered due to the quantum confinement effect or surface oxidation [23–25]. In our experiment, the poles in the Por-Si were macroscale (Fig. 2), that is the PL has nothing to do with quantum size effects. This conclusion can also be proved by the Raman spectra of the samples in Fig. 3. The green mission at about 570 nm in the as-prepared Por-Si may come from sub-oxide silicon complex species, which is confirmed by the FTIR spectra (Fig. 1(b)). After the deposition, a thick C film was covered on the surface (Fig. 2(b)). Therefore, a larger number of carbon atoms could penetrate into the pores and then modify or passivate the surface states, resulting in the PL change of Por-Si (Fig. 1(a)). Furthermore, after the deposition, the intensity of the Si–O–Si vibration bands strongly increased (Fig. 1(b)), which may also explain why the light emission became more efficient, though the deposition damage occurring in the deposited process may affect the efficiency of the PL emission, which can be found in the SEM images, as shown in Fig. 2. In some papers [21,22], the authors assume that the C–Si bonds can produce the blue emission, so the blue emission in our samples may partially come from the C–Si bonds in the surface of the samples. After the RTPs, it was found that the PL intensity of the carbonized Por-Si has changed. The RTP temperature dependence of the PL intensities is shown in Fig. 4. The PL intensity in the samples treated at 800 and 900 1C increased,
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Fig. 2. SEM images of the surface structure of Por-Si. (a) as-prepared Por-Si sample; (b) carbonized Por-Si sample. Inset image is the EDS of the carbonized sample.
Intensity(a.u.)
3000
520
2000 1000
carbon coating Por-S origin Por-S
0 400
800
1200 -1
Raman shift(cm )
Fig. 3. The Raman spectrum of different Por-Si.
while that in the samples treated at the other temperatures is completely quenched. There are several reasons that are responsible for the change in the PL intensity during RTPs, such as desorption of the hydrogen, the Si–C bonds evolution, the thermal stress and the deposited damage, and so on. During the RTP at the low temperatures, the desorption of hydrogen on the surface of Por-Si samples may take place, which may be used to form the dangling bonds and the physical adsorption of the carbon atoms on the surface of Por-Si leads to poorly passivate the irradiative centers or to weakly repair the damage of the plasma plantation, so the PL is quenched. In addition, the physical adsorption of the carbon atoms on the surface
ARTICLE IN PRESS Y. Zhao et al. / Journal of Luminescence 128 (2008) 317–320
320 700
result in a stronger emission at 450 nm, which may be due to the formation of C–Si bonds on the surfaces or the enhanced oxidation. During RTPs, the PL could be increased if the temperatures were 800 and 900 1C. The reason might be the changing of the surface states of the Por-Si samples.
Intensity(a.u.)
600 500 400 300 200 100
References
0 500 600 700 800 900 1000 1100 Temperature(°C)
Fig. 4. Maximum intensities and the peak positions of the PL of the carbonized Por-Si treated by RTP as a function of the temperature.
of Por-Si cannot evolute into the abundant and efficient Si–C emitter at this low temperature, which may be related to the blue emission. Under high temperature, the formation of chemical silicon–carbon bonds is more probable when the carbon atoms penetrated into the pores of Por-Si and interacted with fine structure on the Por-Si skeleton. The carbon–silicon chemical bonds can passivate the dangling bonds due to desorption of the hydrogen atoms from the surface and consequently create new centers (Si–C bonds) for luminescence recombination. Moreover the elimination of implantation damage is more efficient under high temperature, so the appearance of the intense PL in high temperature is reasonable. When the sample was treated in 1000 and 1100 1C under Ar atmosphere, the carbon atoms are dispersed into the Por-Si matrix, which leads to the disappearance of the Si–C bonds on the surface of Por-Si samples. In this situation, a lot of dangling bonds were created, which acted as irradiative center to quench the efficient PL. Furthermore, the contributions of the Si–C bonds on the blue emission also disappear in this condition. In addition, the large heating rate and the cooling down rate during high-temperature rapid thermal treatment result in a strong stress in Por-Si, which induces modification in the energy levels and wave functions of electronic states of the luminescence centers. So the strong stress at the surface of the Por-Si may be the other reason to quench the PL spectrum under hightemperature condition. 4. Conclusions The PL of the carbonized Por-Si before and after RTPs was investigated. It was pointed out that the carbon could
[1] L.T. Canham, Appl. Phys. Lett. 57 (1990) 1046. [2] L. Debarge, J.P. Stoquert, A. Slaoui, L. Stalmans, J. Poortmans, Mater. Sci. Semicond.Process. 1 (1998) 281. [3] W. Lang, P. Steiner, F. Kozlowski, P. Ramm, Thin Solid Films 255 (1995) 224. [4] K.-H. Li, C. Tsai, J.C. Campbell, B.K. Hance, J.M. White, Appl. Phys. Lett. 62 (26) (1993) 3501. [5] H. Chen, X. Hou, G. Li, F. Zhang, M. Yu, X. Wang, J. Appl. Phys. 79 (6) (1996) 3282. [6] G.-B. Li, L.-S. Liao, X.-B. Liu, X.-Y. Hou, X. Wang, Appl. Phys. Lett. 70 (10) (1997) 1284. [7] G. Li, X. Hou, S. Yuan, H. Chen, F. Zhang, H. Fan, X. Wang, J. Appl. Phys. 80 (10) (1996) 5967. [8] K. Kimoto, T. Arai, Phys.StatusSolidi (a) 182 (2000) 133. [9] A.J. Kontkiewicz, A.M. Kontkiewicz, J. Siejka, S. Sen, G. Nowak, A.M. Hoff, P. Sakthivel, K. Ahmed, P. Mukherjee, S. Witanachchi, J. Lagowski, Appl. Phys. Lett. 65 (11) (1994) 1436. [10] H. Tamura, M. Rtickschloss, T. Wirschem, S. Vepiek, Appl. Phys. Lett. 65 (12) (1994) 1537. [11] J. Yan, S. Shih, K.H. Jung, D.L. Kwong, M. Kovar, J.M. White, B.E. Gnade, L. Magel, Appl. Phys. Lett. 64 (11) (1994) 1374. [12] N. Ott, M. Nerding, G. Muller, R. Brendel, H.P. Strunk, J. Appl. Phys. 95 (2) (2004) 497. [13] B.M. Kostishko, I.P. Puzov, Y.S. Nagornov, Tech. Phys. Lett. 26 (1) (2000) 26. [14] O.M. Sreseli, D.N. Goryachev, V.Y. Osipov, L.V. Belyakov, S.P. Vul, I.T. Serenkov, V.I. Sakharov, A.Y. Vul, Semiconductors 36 (5) (2002) 574. [15] X.L. Wu, G.G. Siu, M.J. Stokes, D.L. Fan, Y. Gu, X.M. Bao, Appl. Phys. Lett. 77 (9) (2000) 1292. [16] G. Beshkov, V. Krastev, N. Velchev, T. Marinova, Mater. Sci. Eng. B 56 (1998) 1. [17] Y.P. Piryatinski, V.A. Semenovich, N.I. Klyu, A.G. Rozhin, Tech. Phys. 43 (4) (1998) 423. [18] S.-Y. Wang, W.-Z. Shen, X.-C. Shen, L. Zhu, Z.-M. Ren, Y.-F. Li, K.-F. Liu, Appl. Phys. Lett. 67 (6) (1995) 783. [19] V.A. Makara, N.I. Klyui, A.G. Rozhin, V.G. Litovchenko, Y.P. Piryatinskii, O.B. Korneta, Phys. Status Solidi (a) 197 (2) (2003) 355. [20] V. Baranauskas, B.B. Li, A.C. Peterlevitz, M.C. Tosin, S.F. Durrant, Thin Solid Films 355–356 (1999) 233. [21] J. Salonen, E. Laine, L. Niinisto, J. Appl. Phys. 91 (1) (2002) 456. [22] B.M. Kostishko, S.R. Atazhanov, S.N. Mikov, Tech. Phys. Lett. 24 (8) (1998) 633. [23] J.L. Gole, F.P. Dudel, D. Grantier, Phys. Rev. B 56 (4) (1997) 2137. [24] F.P. Dudel, M.M. Rieger, J.P. Pickering, J.L. Gole, P.A. Kohl, L.A. Bottomley, J. Electrochem. Soc. 143 (8) (1996) L164. [25] F.P. Dudel, J.L. Gole, J. Appl. Phys. 82 (1) (1997) 402.
Journal of Luminescence 128 (2008) 317–320 www.elsevier.com/locate/jlumin
Effect of rapid thermal treatment on photoluminescence of surface passivated porous silicon Yue Zhaoa,b,, Dongsheng Lib, Shuoxiang Xingc, Wenbin Sanga, Deren Yangb, Minhua Jiangb,d a
Department of Electronic Information Materials, Shanghai University, Shanghai 200072, China b State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310027, China c Clean Energy and Environment Engineering Key Laboratory of Ministry of Education, Zhejiang University, Hangzhou 310027, China d State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, PR China Received 4 June 2005; received in revised form 9 April 2007; accepted 9 April 2007 Available online 6 August 2007
Abstract The photoluminescence of porous silicon with and without carbon deposition fabricated by plasma-enhanced chemical vapor deposition technique has been investigated. After the deposition, the rapid thermal processes in the temperature ranging from 500 to 1100 1C have been carried out. It was found that after the carbon deposition a new intense blue emission appeared. The rapid thermal processes at 800and 900 1C could enhance the blue emission, while the other rapid thermal processes quenched it. Finally, the mechanism for the effect of carbon deposition and rapid thermal processes on photoluminescence properties of porous silicon was discussed. r 2007 Elsevier B.V. All rights reserved. Keywords: Porous silicon; Blue emission; Rapid thermal processes
1. Introduction After the photoluminescence (PL) of electrochemically etched porous silicon (Por-Si) was reported in 1990 [1], it has become an attractive material in the field of electronics and opto-electronics. However, the large amounts of highly reactive internal surface of Por-Si compared with bulk Si increase drastically its sensitivity to air. To overcome the degradation of PL intensity with time, post-treatment processes, such as rapid thermal oxidation [2–6], rapid thermal processes (RTPs) under NH3 or N2 atmosphere [7–9], high-and low-temperature processes under different atmospheres [10–13], are used to passivate Por-Si. These post-treatment processes greatly enhance and stabilize the PL of Por-Si. In addition, silicon–carbon bonds can be also used to passivate the surface of Por-Si, Corresponding author. State Key Laboratory of Silicon Materials, Zhejiang University, Zheda Road 38, Hangzhou 310027, China, Tel.: +86 571 87951667; fax: +86 571 87952322. E-mail address: [email protected] (Y. Zhao).
0022-2313/$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2007.04.015
because the bonds protect from the oxidation of the Por-Si surface. Several groups have investigated the formation of silicon–carbon bonds on Por-Si by means of different techniques including the two-step wet chemical technique [14,15], magnetron controlled sputtering [16], capacitive RF discharge plasma deposition [17], ionized cluster beam deposition [18], chemical vapor deposition [19], hot filament chemical vapor deposition [20] and thermally carbonized process [21,22]. The carbonized Por-Si has been observed to be stable in various chemical environments. These results also showed that the structure of carbonized Por-Si has the stable and efficient luminescence in visible spectral range. In this paper, we investigated the luminescence of Por-Si carbonized by plasma enhancement chemical vapor deposition (PECVD) method. In PECVD process, the deposited film can be produced in a very large area and at low temperature, which is beneficial for device fabrication. After the deposited processes, rapid thermal processes (RTPs) that are now widely employed in the microelectronic industry were used as the post-treatments.
ARTICLE IN PRESS 318
Y. Zhao et al. / Journal of Luminescence 128 (2008) 317–320
2. Experiments 2
3. Results and discussions Fig. 1 (a) depicts the PL spectra of the as prepared and the carbonized Por-Si. The corresponding FTIR spectra of the two types of samples are shown in Fig. 1(b). A PL peak centered at 570 nm is observed in the as-prepared Por-Si samples (Fig. 1. a (1)). After the deposition of C film on the Por-Si surface, a new blue band centered at about 450 nm (Fig. 1. a (2)) and the peak at 570 nm increases slightly. Compared with the as-prepared PS, the Si–O–Si related FTIR vibration bands at 1084 cm 1 and 463 cm 1 are largely strengthened in the carbonized Por-Si (Fig. 1b). This means that during the C deposition, the PS was oxidized. The SEM images of the surface structure of the asprepared and carbonized Por-Si samples are shown in Fig. 2. The two samples have the same columnar structure. It can be seen from Fig. 2 that after the C deposition the fine structure of the as-prepared sample was lost, and a thick film was formed on the surface, resulting in the generation of C–Si bonds. In Fig. 2(b), the inset image is the energy dispersive spectral of the carbonized sample. The weak C peak is shown in this picture, which indicated that the C atoms were attached on the surface of the carbonized samples and may affect the PL property of this sample.
Intensity(a.u.)
60 40 20 1
0 400
500 600 Wavelength(nm)
700
1084
4
920
2
463
3
610
Absorptance(a.u.)
(1 0 0)-oriented and boron-doped polished single crystal Si wafers with a resistivity of 10-20 O cm were used to prepare Por-Si samples. The anodization was conducted in a solution of HF:C2H5OH=1:2 at room temperature. The constant current density was 50 mA/cm2 and the etched time was 60 min. Before being etched, the back of the wafers was deposited with Al by thermal evaporation to provide an ohmic contact. After the fabrication of Por-Si, the samples were rinsed with de-ionized water and dried in air. Then, the backside Al film was removed with aqueous HF. The C films were deposited by the PECVD method. The source gas was C2H2 and the substrate temperature was 1601C. The C2H2 flow rate was 20 sccm. The deposition pressure was kept at 6 Pa and the power was at 30 W. After the deposition, the RTPs were carried out for 30 s in the temperature ranging from 500 to 1100 1C in Ar atmosphere. The Ar flux was about 1.5 L/min. The heating rate and the cooling rate were about 50 1C/s. The samples were characterized by PL spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The PL spectra excited by a Xe lamp at 360 nm wavelength were measured with a HITACHI F-4500 fluorescence spectrophotometer. The infrared absorption spectra were taken by using a Bruker IFS 66v/S FTIR spectroscope. The appearance observations were carried out by JSM-5610LV SEM. All the measurements were carried out at room temperature.
2 1
1
500
1000
1500
2000
Wavenumber(cm-1)
Fig. 1. PL spectra (a) and FTIR spectra (b) of the samples. (1) asprepared Por-Si samples; (2) the samples deposited with carbon.
The PL of Por-Si has been considered due to the quantum confinement effect or surface oxidation [23–25]. In our experiment, the poles in the Por-Si were macroscale (Fig. 2), that is the PL has nothing to do with quantum size effects. This conclusion can also be proved by the Raman spectra of the samples in Fig. 3. The green mission at about 570 nm in the as-prepared Por-Si may come from sub-oxide silicon complex species, which is confirmed by the FTIR spectra (Fig. 1(b)). After the deposition, a thick C film was covered on the surface (Fig. 2(b)). Therefore, a larger number of carbon atoms could penetrate into the pores and then modify or passivate the surface states, resulting in the PL change of Por-Si (Fig. 1(a)). Furthermore, after the deposition, the intensity of the Si–O–Si vibration bands strongly increased (Fig. 1(b)), which may also explain why the light emission became more efficient, though the deposition damage occurring in the deposited process may affect the efficiency of the PL emission, which can be found in the SEM images, as shown in Fig. 2. In some papers [21,22], the authors assume that the C–Si bonds can produce the blue emission, so the blue emission in our samples may partially come from the C–Si bonds in the surface of the samples. After the RTPs, it was found that the PL intensity of the carbonized Por-Si has changed. The RTP temperature dependence of the PL intensities is shown in Fig. 4. The PL intensity in the samples treated at 800 and 900 1C increased,
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319
Fig. 2. SEM images of the surface structure of Por-Si. (a) as-prepared Por-Si sample; (b) carbonized Por-Si sample. Inset image is the EDS of the carbonized sample.
Intensity(a.u.)
3000
520
2000 1000
carbon coating Por-S origin Por-S
0 400
800
1200 -1
Raman shift(cm )
Fig. 3. The Raman spectrum of different Por-Si.
while that in the samples treated at the other temperatures is completely quenched. There are several reasons that are responsible for the change in the PL intensity during RTPs, such as desorption of the hydrogen, the Si–C bonds evolution, the thermal stress and the deposited damage, and so on. During the RTP at the low temperatures, the desorption of hydrogen on the surface of Por-Si samples may take place, which may be used to form the dangling bonds and the physical adsorption of the carbon atoms on the surface of Por-Si leads to poorly passivate the irradiative centers or to weakly repair the damage of the plasma plantation, so the PL is quenched. In addition, the physical adsorption of the carbon atoms on the surface
ARTICLE IN PRESS Y. Zhao et al. / Journal of Luminescence 128 (2008) 317–320
320 700
result in a stronger emission at 450 nm, which may be due to the formation of C–Si bonds on the surfaces or the enhanced oxidation. During RTPs, the PL could be increased if the temperatures were 800 and 900 1C. The reason might be the changing of the surface states of the Por-Si samples.
Intensity(a.u.)
600 500 400 300 200 100
References
0 500 600 700 800 900 1000 1100 Temperature(°C)
Fig. 4. Maximum intensities and the peak positions of the PL of the carbonized Por-Si treated by RTP as a function of the temperature.
of Por-Si cannot evolute into the abundant and efficient Si–C emitter at this low temperature, which may be related to the blue emission. Under high temperature, the formation of chemical silicon–carbon bonds is more probable when the carbon atoms penetrated into the pores of Por-Si and interacted with fine structure on the Por-Si skeleton. The carbon–silicon chemical bonds can passivate the dangling bonds due to desorption of the hydrogen atoms from the surface and consequently create new centers (Si–C bonds) for luminescence recombination. Moreover the elimination of implantation damage is more efficient under high temperature, so the appearance of the intense PL in high temperature is reasonable. When the sample was treated in 1000 and 1100 1C under Ar atmosphere, the carbon atoms are dispersed into the Por-Si matrix, which leads to the disappearance of the Si–C bonds on the surface of Por-Si samples. In this situation, a lot of dangling bonds were created, which acted as irradiative center to quench the efficient PL. Furthermore, the contributions of the Si–C bonds on the blue emission also disappear in this condition. In addition, the large heating rate and the cooling down rate during high-temperature rapid thermal treatment result in a strong stress in Por-Si, which induces modification in the energy levels and wave functions of electronic states of the luminescence centers. So the strong stress at the surface of the Por-Si may be the other reason to quench the PL spectrum under hightemperature condition. 4. Conclusions The PL of the carbonized Por-Si before and after RTPs was investigated. It was pointed out that the carbon could
[1] L.T. Canham, Appl. Phys. Lett. 57 (1990) 1046. [2] L. Debarge, J.P. Stoquert, A. Slaoui, L. Stalmans, J. Poortmans, Mater. Sci. Semicond.Process. 1 (1998) 281. [3] W. Lang, P. Steiner, F. Kozlowski, P. Ramm, Thin Solid Films 255 (1995) 224. [4] K.-H. Li, C. Tsai, J.C. Campbell, B.K. Hance, J.M. White, Appl. Phys. Lett. 62 (26) (1993) 3501. [5] H. Chen, X. Hou, G. Li, F. Zhang, M. Yu, X. Wang, J. Appl. Phys. 79 (6) (1996) 3282. [6] G.-B. Li, L.-S. Liao, X.-B. Liu, X.-Y. Hou, X. Wang, Appl. Phys. Lett. 70 (10) (1997) 1284. [7] G. Li, X. Hou, S. Yuan, H. Chen, F. Zhang, H. Fan, X. Wang, J. Appl. Phys. 80 (10) (1996) 5967. [8] K. Kimoto, T. Arai, Phys.StatusSolidi (a) 182 (2000) 133. [9] A.J. Kontkiewicz, A.M. Kontkiewicz, J. Siejka, S. Sen, G. Nowak, A.M. Hoff, P. Sakthivel, K. Ahmed, P. Mukherjee, S. Witanachchi, J. Lagowski, Appl. Phys. Lett. 65 (11) (1994) 1436. [10] H. Tamura, M. Rtickschloss, T. Wirschem, S. Vepiek, Appl. Phys. Lett. 65 (12) (1994) 1537. [11] J. Yan, S. Shih, K.H. Jung, D.L. Kwong, M. Kovar, J.M. White, B.E. Gnade, L. Magel, Appl. Phys. Lett. 64 (11) (1994) 1374. [12] N. Ott, M. Nerding, G. Muller, R. Brendel, H.P. Strunk, J. Appl. Phys. 95 (2) (2004) 497. [13] B.M. Kostishko, I.P. Puzov, Y.S. Nagornov, Tech. Phys. Lett. 26 (1) (2000) 26. [14] O.M. Sreseli, D.N. Goryachev, V.Y. Osipov, L.V. Belyakov, S.P. Vul, I.T. Serenkov, V.I. Sakharov, A.Y. Vul, Semiconductors 36 (5) (2002) 574. [15] X.L. Wu, G.G. Siu, M.J. Stokes, D.L. Fan, Y. Gu, X.M. Bao, Appl. Phys. Lett. 77 (9) (2000) 1292. [16] G. Beshkov, V. Krastev, N. Velchev, T. Marinova, Mater. Sci. Eng. B 56 (1998) 1. [17] Y.P. Piryatinski, V.A. Semenovich, N.I. Klyu, A.G. Rozhin, Tech. Phys. 43 (4) (1998) 423. [18] S.-Y. Wang, W.-Z. Shen, X.-C. Shen, L. Zhu, Z.-M. Ren, Y.-F. Li, K.-F. Liu, Appl. Phys. Lett. 67 (6) (1995) 783. [19] V.A. Makara, N.I. Klyui, A.G. Rozhin, V.G. Litovchenko, Y.P. Piryatinskii, O.B. Korneta, Phys. Status Solidi (a) 197 (2) (2003) 355. [20] V. Baranauskas, B.B. Li, A.C. Peterlevitz, M.C. Tosin, S.F. Durrant, Thin Solid Films 355–356 (1999) 233. [21] J. Salonen, E. Laine, L. Niinisto, J. Appl. Phys. 91 (1) (2002) 456. [22] B.M. Kostishko, S.R. Atazhanov, S.N. Mikov, Tech. Phys. Lett. 24 (8) (1998) 633. [23] J.L. Gole, F.P. Dudel, D. Grantier, Phys. Rev. B 56 (4) (1997) 2137. [24] F.P. Dudel, M.M. Rieger, J.P. Pickering, J.L. Gole, P.A. Kohl, L.A. Bottomley, J. Electrochem. Soc. 143 (8) (1996) L164. [25] F.P. Dudel, J.L. Gole, J. Appl. Phys. 82 (1) (1997) 402.