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Cathodoluminescence study on the tilt and twist boundaries in bonded silicon wafers
Materials Science and Engineering B91– 92 (2002) 244– 247 www.elsevier.com/locate/mseb
Cathodoluminescence study on the tilt and twist boundaries in bonded silicon wafers T. Sekiguchi a,*, S. Ito b, A. Kanai c a
Nanomaterials Laboratory, National Institute for Materials Science, Tsukuba 305 -0047, Japan b Institute for Materials Research, Tohoku Uni6ersity, Sendai 980 -8577, Japan c Naoetsu Electronics Co. Ltd., Kubiki-mura 942 -0193, Japan
Abstract We have fabricated artificial tilt and twist boundaries of Si by direct bonding technique. Transmission electron microscopy (TEM) showed that the arrays of edge dislocations were formed at the tilt boundaries, while the square networks of screw dislocations were formed at the twist boundaries according to the misorientation angles. Several peaks were observed in cathodoluminescence (CL) spectra, which may be attributed to the D-lines of dislocation luminescence. Although it is rather difficult to correlate these spectra with certain structures of boundaries, a plausible explanation was given in terms of straightness of dislocation line and dislocation density. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Silicon; Hydrogen; Grain boundaries; Dislocation; Cathodoluminescence; D-line
1. Introduction Direct bonding is a promising technique to fabricate artificial structures such as abrupt p – n junctions, multilayered structures that are difficult to produce by usual processes etc. Even in the bonding of flat surface wafers, the misorientation of two wafers inevitably introduces a distinct grain boundary at the interface [1 –4]. Such a grain boundary may be represented as the ideal dislocation network. It is well known that plastically deformed silicon crystals have characteristic luminescence, called D-lines [5]. It is a set of four lines located at 0.81, 0.87, 0.93, and 1.00 eV. They are denoted by D1, D2, D3 and D4, respectively. Many researchers have investigated the origin of D-lines [6 – 12]. Cathodoluminescence (CL) has the advantage that it can give us the information of spatial distribution of luminescence centers. Sekiguchi and Sumino [12] prepared deformed specimens with various types of dislocation configuration and observed CL images. They concluded that D3 and D4 arise from
* Corresponding author. Tel.: + 81-298-59-2750; fax: +81-298-592701. E-mail address: [email protected] (T. Sekiguchi).
the glide dislocations while D1 and D2 arise from the reaction products of dislocations. In this paper, we have prepared various types of tilt and twist boundaries by the direct bonding technique and obtained their CL spectra to correlate the luminescence lines with the structures of grain boundaries.
2. Experimental Artificial grain boundaries were fabricated by direct bonding technique. The (001) oriented Cz-grown Si wafers and vicinal wafers of 4-in. size were prepared. They were n-type and their resistivity was 4–6 Vcm. The wafers were immersed in a HF solution (1.5%) to remove surface oxide layers. For tilt boundaries, two identical vicinal wafers were put together by overlapping their orientation-flats. For twist boundaries, two (001) wafers were put together with certain twist angles. After the bonding at room temperature, the wafers were annealed at 1100 °C for 2 h in dry O2 atmosphere to promote rearrangement of atoms at the boundaries. The tilt and twist angles of the boundaries were measured by X-ray diffractometry. Table 1 shows the condition of specimens used in this study. At present, the precise control of twist angle is difficult, so that we
0921-5107/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 5 1 0 7 ( 0 1 ) 0 1 0 2 0 - 0
T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
regard the boundaries of specimen I and V as the 1(001). Pieces of the bonded wafers including the (110) intersection were cut from the wafer and were mechanically and chemically polished by Carborundum and CP4, respectively. One set of specimens was prepared for transmission electron microscopy (TEM) to observe the structure of the grain boundary. Some of the specimens were immersed in hydrogen plasma at 400 °C for 6 min to passivate nonradiative recombination centers [11]. CL observation was done using an electron beam tester [13] at 21 K with an electron beam of 20 kV and 50 nA. InGaAs multi-channelplate (Jobin Yvon, IGA512x1-1) was adapted for spectrum acquisition, while a Ge-detector (North Coast, EO817L) with band pass filters [11] was used for CL imaging. 3. Results and discussion TEM images of the 1(001) and tilt boundaries are shown in Fig. 1. The tilt angles are 0, 0.4, and 1.0° for the upper, middle and lower columns, respectively. The left rows are edge-on images of grain boundary (110 zone axis), while right rows are tilted images (111 zone axis). No defects except oxygen precipitates of hexagonal platelet were seen in the edge-on images. The density of oxygen precipitates in all the specimens was 5–7× 109 cm − 2 irrespective of the misorientation angles. In the tilted image, on the other hand, the dislocation networks of grain boundaries are clearly observed. The 1 (001) boundary consists of a regularly arranged square network of screw dislocations due to the small twist angle. In contrast, 0.4 and 1.0° tilt boundaries are composed of regularly arrayed edge dislocations. The dislocations in 0.4° tilt boundary are, however, not straight probably due to the compensation of twist component (0.2°). The TEM images of twist boundaries were similar to those presented by Ikeda et al. [14], which were composed of a square mesh of screw dislocations. The spacing of dislocation corresponded to the value estimated from the misorientation angle. Table 1 Condition of bonding wafers Number
Type of boundary
Tilt angle (°)
Twist angle (°)
I
1(001) or twist/0.3° Tilt/0.4° Tilt/1.0° Tilt/6° 1(001) or twist/0.4° Twist/1.5° Twist/3°
0.037
0.289
0.385 0.968 5.890 0.013
0.204 0.138 0.059 0.403
0.020 0.016
1.553 2.929
II III IV V VI VII
245
We first observed CL spectra and images of various interfaces in as-bonded state. In some specimens, however, the interface was imaged as a dark line in all the D-line CL images. This means that nonradiative recombination centers were introduced at the interface. To avoid such an additional effect, the specimens were immersed in hydrogen plasma to passivate nonradiative centers [11]. After hydrogenation, the interface became bright in D-line CL images. Fig. 2 shows the CL spectra of tilt boundaries as well as the 1(001). Since oxygen precipitates may have little contribution to the CL spectra or give similar backgrounds on the CL spectra, we may ignore the effect of oxygen precipitation. Thus, we may analyze the CL spectra in terms of dislocation related luminescence, namely D-lines. The 1(001) boundary, whose twist angle was 0.4°, has five peaks at 0.82, 0.93, 1.00, 1.04 and 1.10 eV. The latter two peaks are attributed to the transverse optical phonon replica of excitonic luminescence (1.10 eV) and its OG phonon replica (1.04 eV), which are inherent in the Si crystal. Contrary to these, the former three are related to the boundary, which was confirmed with the fact that these emission intensities became maximum at the boundary. They may correspond to D1 (0.82 eV), D3 (0.93 eV) and D4 (1.00 eV). On the other hand, 0.4° tilt boundary shows no characteristic emission in the range between 0.8 and 1.0 eV. The 1.0° tilt boundary again shows four characteristic peaks at 0.84, 0.90, 0.95 and 0.99 eV in addition to the intrinsic luminescence. We may correlate them to D1, D2, D3 and D4, respectively. Since rather straight edge dislocations are regularly arrayed at this interface, all the D-lines can be observed. The 6° tilt boundary shows the indistinct spectrum. Only one broad peak centered at 0.92 eV was identified. Fig. 3 shows the CL spectra of twist boundaries. In this case, specimen I and V were regarded as 0.3 and 0.4° twist boundaries, respectively. The 0.3° twist boundary has five peaks at 0.82, 0.93, 0.99, 1.04 and 1.10 eV. These peaks are attributed D1, D3, D4 and two phonon replicas of excitonic luminescence. This spectrum is almost the same as that of 0.4° twist boundary, except the peak position and feature of D1 line. The 1.5° twist boundary also shows similar spectrum although the peak was rather blurred. On the other hand, the 3° twist boundary has only one intense broad peak at 0.85–0.87 eV. One shoulder was observed at 0.79 eV. To explain these spectra systematically, we calculated the spacing of dislocation networks and dislocation density of each specimen. Table 2 shows these values as well as the appearance of D-lines. D1, D3 and D4 are observed in specimens I, III, V and VI. D2 is observed only in specimen III. These specimens are small tilt or twist boundaries. This suggests that the dislocations in such boundaries may have similar defect state to the
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T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
Fig. 1. TEM images of (a, d) 1(001) [specimen I], (b, e) 0.4° [specimen II] and (c, f) 1.0° [specimen III] tilt boundaries. (a, b, c) edge-on images (110 zone axis), (d, e, f) tilted images (111 zone axis).
glide dislocations, irrespective of edge or screw. The absence of D-lines in the 0.4° tilt boundary might be attributed to the winding shape of edge dislocations. Such irregular structure has brought about by the compensation of unnegligible twist component. Both 6 tilt and 3° twist boundaries have broad peaks, which cannot be categorized in D-lines. In these boundaries the spacing of dislocation was less than 10 nm. The overlap of energy state or deformation potential of dislocation might be the cause of these unknown emissions. The intensities of D-lines were similar in the specimens I, V and VI. In these boundaries, however, the dislocation density varies from 26 to 142 mm − 1. Thus, the D-line intensity does not depend on the dislocation density. This result suggests that the carrier recombination at the grain boundary is not dominated
by the number of recombination centers but by the carrier diffusion process. It infers the existence of band bending at the grain boundary. According to Sekiguchi and Sumino [12], D1 and D2 originate from the product of dislocation interaction, namely Lomer–Cottrell dislocations or jogs. In this study, there exists little evidence about it. We have to wait this answer before we can fabricate ideal grain boundaries.
4. Summary We have succeeded to fabricate artificial tilt and twist boundaries in Si by direct bonding technique. Square networks of screw dislocations were observed in tilt
T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
247
Table 2 Estimated spacing of dislocation network and dislocation density Density (1 per mm)
Number
Type of boundary
a
D2
D3
D4
Spacing (nm)
b
I II III IV V VI VII
1(001) or twist/0.3° Tilt/0.4° Tilt/1.0° Tilt/6° 1(001) or twist/0.4° Twist/1.5° Twist/3°
á – á I á á I
– – á I – – á
– á –
– I –
55 57 23 3.7 76 14 7.5
26 18 43 270 36 142 266
a b
D1
The D-line intensity is expressed as, á, strong; , fair; , weak; –, not detected; I, emission but no peak. Dislocation density is expressed with the number of dislocation include in the cross section of 1 mm.
Fig. 2. CL spectra of tilt boundaries as well as the 1(001). 0°-specimen V, 0.4°-specimen II, 1.0°-specimen III, 6°-specimen IV. Taken at 21 K with an electron beam of 20 kV, 50 nA.
Fig. 3. CL spectra of twist boundaries. 0.3°-specimen I, 0.4°-specimen V, 1.5°-specimen VI, 3°-specimen VII. Taken at 21 K with an electron beam of 20 kV, 50 nA.
boundaries, while arrays of edge dislocations were observed in twist boundaries. In CL spectra, D-lines are observed in small angle tilt or twist boundaries. No luminescence related to grain boundaries was observed from the winding dislocation arrays in the 0.4° tilt boundaries. Broad luminescence was observed from the 6 tilt and 3° twist boundaries.
[4] K. Ikeda, T. Sekiguchi, S. Ito, M. Suezawa, Solid State Phenom. 63 – 64 (1998) 481. [5] N.A. Drozdov, A.A. Patrin, V.D. Tkachev, Pis’ma Zh. Eksp. Teor. Fiz. 23 (1976) 651 [JETP Lett. 23 597 (1976)]. [6] M. Suezawa, Y. Sasaki, K. Sumino, Phys. Status Solidi A 79 (1983) 173. [7] R. Sauer, J. Weber, J. Stolz, E.R. Weber, K.-H. Kusters, H. Alexander, Appl. Phys. A 36 (1985) 1. [8] Y.u. Lerikov, Y.u. Rebane, S. Ruvimov, D. Tarhin, A. Sitnikova, Y.u. Shreter, Mater. Sci. Forum 83 – 87 (1992) 1321. [9] K. Weronek, J. Weber, A. Hopner, F. Ernst, R. Buchner, M. Stefaniak, H. Alexander, Mater. Sci. Forum 83 – 87 (1992) 1315. [10] V. Higgs, E.C. Lightowlers, C.E. Norman, P.C. Kightley, Proc. 16th International Conference on Defects in Semiconductors, Materials Science Forum, 1992, 83 – 87, pp. 1309. [11] T. Sekiguchi, V.V. Kveder, K. Sumino, J. Appl. Phys. 76 (1995) 7882. [12] T. Sekiguchi, K. Sumino, J. Appl. Phys. 76 (1996) 3253. [13] T. Sekiguchi, K. Sumino, Rev. Sci. Instrum. 66 (1995) 4277. [14] K. Ikeda, T. Sekiguchi, S. Ito, M. Takebe, M. Suezawa, J. Crystal Growth 210 (2000) 90.
References [1] A.P. Sutton, R.W. Balluffi, Interfaces in Crystalline Materials, Oxford University Press, 1996. [2] U. Gosele, H. Stenzel, M. Reiche, T. Martini, H. Steinkirchner, Q.-Y. Tong, Solid State Phenom. 47 –48 (1996) 33. [3] M. Benamara, A. Rocher, P. Sopena, A. Claverie, A. Laporte, G. Sarrabayrouse, L. Lescouzeres, A. Peyre-Lavigne, Mat. Sci. Eng. B42 (1996) 164.
Cathodoluminescence study on the tilt and twist boundaries in bonded silicon wafers T. Sekiguchi a,*, S. Ito b, A. Kanai c a
Nanomaterials Laboratory, National Institute for Materials Science, Tsukuba 305 -0047, Japan b Institute for Materials Research, Tohoku Uni6ersity, Sendai 980 -8577, Japan c Naoetsu Electronics Co. Ltd., Kubiki-mura 942 -0193, Japan
Abstract We have fabricated artificial tilt and twist boundaries of Si by direct bonding technique. Transmission electron microscopy (TEM) showed that the arrays of edge dislocations were formed at the tilt boundaries, while the square networks of screw dislocations were formed at the twist boundaries according to the misorientation angles. Several peaks were observed in cathodoluminescence (CL) spectra, which may be attributed to the D-lines of dislocation luminescence. Although it is rather difficult to correlate these spectra with certain structures of boundaries, a plausible explanation was given in terms of straightness of dislocation line and dislocation density. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Silicon; Hydrogen; Grain boundaries; Dislocation; Cathodoluminescence; D-line
1. Introduction Direct bonding is a promising technique to fabricate artificial structures such as abrupt p – n junctions, multilayered structures that are difficult to produce by usual processes etc. Even in the bonding of flat surface wafers, the misorientation of two wafers inevitably introduces a distinct grain boundary at the interface [1 –4]. Such a grain boundary may be represented as the ideal dislocation network. It is well known that plastically deformed silicon crystals have characteristic luminescence, called D-lines [5]. It is a set of four lines located at 0.81, 0.87, 0.93, and 1.00 eV. They are denoted by D1, D2, D3 and D4, respectively. Many researchers have investigated the origin of D-lines [6 – 12]. Cathodoluminescence (CL) has the advantage that it can give us the information of spatial distribution of luminescence centers. Sekiguchi and Sumino [12] prepared deformed specimens with various types of dislocation configuration and observed CL images. They concluded that D3 and D4 arise from
* Corresponding author. Tel.: + 81-298-59-2750; fax: +81-298-592701. E-mail address: [email protected] (T. Sekiguchi).
the glide dislocations while D1 and D2 arise from the reaction products of dislocations. In this paper, we have prepared various types of tilt and twist boundaries by the direct bonding technique and obtained their CL spectra to correlate the luminescence lines with the structures of grain boundaries.
2. Experimental Artificial grain boundaries were fabricated by direct bonding technique. The (001) oriented Cz-grown Si wafers and vicinal wafers of 4-in. size were prepared. They were n-type and their resistivity was 4–6 Vcm. The wafers were immersed in a HF solution (1.5%) to remove surface oxide layers. For tilt boundaries, two identical vicinal wafers were put together by overlapping their orientation-flats. For twist boundaries, two (001) wafers were put together with certain twist angles. After the bonding at room temperature, the wafers were annealed at 1100 °C for 2 h in dry O2 atmosphere to promote rearrangement of atoms at the boundaries. The tilt and twist angles of the boundaries were measured by X-ray diffractometry. Table 1 shows the condition of specimens used in this study. At present, the precise control of twist angle is difficult, so that we
0921-5107/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 5 1 0 7 ( 0 1 ) 0 1 0 2 0 - 0
T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
regard the boundaries of specimen I and V as the 1(001). Pieces of the bonded wafers including the (110) intersection were cut from the wafer and were mechanically and chemically polished by Carborundum and CP4, respectively. One set of specimens was prepared for transmission electron microscopy (TEM) to observe the structure of the grain boundary. Some of the specimens were immersed in hydrogen plasma at 400 °C for 6 min to passivate nonradiative recombination centers [11]. CL observation was done using an electron beam tester [13] at 21 K with an electron beam of 20 kV and 50 nA. InGaAs multi-channelplate (Jobin Yvon, IGA512x1-1) was adapted for spectrum acquisition, while a Ge-detector (North Coast, EO817L) with band pass filters [11] was used for CL imaging. 3. Results and discussion TEM images of the 1(001) and tilt boundaries are shown in Fig. 1. The tilt angles are 0, 0.4, and 1.0° for the upper, middle and lower columns, respectively. The left rows are edge-on images of grain boundary (110 zone axis), while right rows are tilted images (111 zone axis). No defects except oxygen precipitates of hexagonal platelet were seen in the edge-on images. The density of oxygen precipitates in all the specimens was 5–7× 109 cm − 2 irrespective of the misorientation angles. In the tilted image, on the other hand, the dislocation networks of grain boundaries are clearly observed. The 1 (001) boundary consists of a regularly arranged square network of screw dislocations due to the small twist angle. In contrast, 0.4 and 1.0° tilt boundaries are composed of regularly arrayed edge dislocations. The dislocations in 0.4° tilt boundary are, however, not straight probably due to the compensation of twist component (0.2°). The TEM images of twist boundaries were similar to those presented by Ikeda et al. [14], which were composed of a square mesh of screw dislocations. The spacing of dislocation corresponded to the value estimated from the misorientation angle. Table 1 Condition of bonding wafers Number
Type of boundary
Tilt angle (°)
Twist angle (°)
I
1(001) or twist/0.3° Tilt/0.4° Tilt/1.0° Tilt/6° 1(001) or twist/0.4° Twist/1.5° Twist/3°
0.037
0.289
0.385 0.968 5.890 0.013
0.204 0.138 0.059 0.403
0.020 0.016
1.553 2.929
II III IV V VI VII
245
We first observed CL spectra and images of various interfaces in as-bonded state. In some specimens, however, the interface was imaged as a dark line in all the D-line CL images. This means that nonradiative recombination centers were introduced at the interface. To avoid such an additional effect, the specimens were immersed in hydrogen plasma to passivate nonradiative centers [11]. After hydrogenation, the interface became bright in D-line CL images. Fig. 2 shows the CL spectra of tilt boundaries as well as the 1(001). Since oxygen precipitates may have little contribution to the CL spectra or give similar backgrounds on the CL spectra, we may ignore the effect of oxygen precipitation. Thus, we may analyze the CL spectra in terms of dislocation related luminescence, namely D-lines. The 1(001) boundary, whose twist angle was 0.4°, has five peaks at 0.82, 0.93, 1.00, 1.04 and 1.10 eV. The latter two peaks are attributed to the transverse optical phonon replica of excitonic luminescence (1.10 eV) and its OG phonon replica (1.04 eV), which are inherent in the Si crystal. Contrary to these, the former three are related to the boundary, which was confirmed with the fact that these emission intensities became maximum at the boundary. They may correspond to D1 (0.82 eV), D3 (0.93 eV) and D4 (1.00 eV). On the other hand, 0.4° tilt boundary shows no characteristic emission in the range between 0.8 and 1.0 eV. The 1.0° tilt boundary again shows four characteristic peaks at 0.84, 0.90, 0.95 and 0.99 eV in addition to the intrinsic luminescence. We may correlate them to D1, D2, D3 and D4, respectively. Since rather straight edge dislocations are regularly arrayed at this interface, all the D-lines can be observed. The 6° tilt boundary shows the indistinct spectrum. Only one broad peak centered at 0.92 eV was identified. Fig. 3 shows the CL spectra of twist boundaries. In this case, specimen I and V were regarded as 0.3 and 0.4° twist boundaries, respectively. The 0.3° twist boundary has five peaks at 0.82, 0.93, 0.99, 1.04 and 1.10 eV. These peaks are attributed D1, D3, D4 and two phonon replicas of excitonic luminescence. This spectrum is almost the same as that of 0.4° twist boundary, except the peak position and feature of D1 line. The 1.5° twist boundary also shows similar spectrum although the peak was rather blurred. On the other hand, the 3° twist boundary has only one intense broad peak at 0.85–0.87 eV. One shoulder was observed at 0.79 eV. To explain these spectra systematically, we calculated the spacing of dislocation networks and dislocation density of each specimen. Table 2 shows these values as well as the appearance of D-lines. D1, D3 and D4 are observed in specimens I, III, V and VI. D2 is observed only in specimen III. These specimens are small tilt or twist boundaries. This suggests that the dislocations in such boundaries may have similar defect state to the
246
T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
Fig. 1. TEM images of (a, d) 1(001) [specimen I], (b, e) 0.4° [specimen II] and (c, f) 1.0° [specimen III] tilt boundaries. (a, b, c) edge-on images (110 zone axis), (d, e, f) tilted images (111 zone axis).
glide dislocations, irrespective of edge or screw. The absence of D-lines in the 0.4° tilt boundary might be attributed to the winding shape of edge dislocations. Such irregular structure has brought about by the compensation of unnegligible twist component. Both 6 tilt and 3° twist boundaries have broad peaks, which cannot be categorized in D-lines. In these boundaries the spacing of dislocation was less than 10 nm. The overlap of energy state or deformation potential of dislocation might be the cause of these unknown emissions. The intensities of D-lines were similar in the specimens I, V and VI. In these boundaries, however, the dislocation density varies from 26 to 142 mm − 1. Thus, the D-line intensity does not depend on the dislocation density. This result suggests that the carrier recombination at the grain boundary is not dominated
by the number of recombination centers but by the carrier diffusion process. It infers the existence of band bending at the grain boundary. According to Sekiguchi and Sumino [12], D1 and D2 originate from the product of dislocation interaction, namely Lomer–Cottrell dislocations or jogs. In this study, there exists little evidence about it. We have to wait this answer before we can fabricate ideal grain boundaries.
4. Summary We have succeeded to fabricate artificial tilt and twist boundaries in Si by direct bonding technique. Square networks of screw dislocations were observed in tilt
T. Sekiguchi et al. / Materials Science and Engineering B91–92 (2002) 244–247
247
Table 2 Estimated spacing of dislocation network and dislocation density Density (1 per mm)
Number
Type of boundary
a
D2
D3
D4
Spacing (nm)
b
I II III IV V VI VII
1(001) or twist/0.3° Tilt/0.4° Tilt/1.0° Tilt/6° 1(001) or twist/0.4° Twist/1.5° Twist/3°
á – á I á á I
– – á I – – á
– á –
– I –
55 57 23 3.7 76 14 7.5
26 18 43 270 36 142 266
a b
D1
The D-line intensity is expressed as, á, strong; , fair; , weak; –, not detected; I, emission but no peak. Dislocation density is expressed with the number of dislocation include in the cross section of 1 mm.
Fig. 2. CL spectra of tilt boundaries as well as the 1(001). 0°-specimen V, 0.4°-specimen II, 1.0°-specimen III, 6°-specimen IV. Taken at 21 K with an electron beam of 20 kV, 50 nA.
Fig. 3. CL spectra of twist boundaries. 0.3°-specimen I, 0.4°-specimen V, 1.5°-specimen VI, 3°-specimen VII. Taken at 21 K with an electron beam of 20 kV, 50 nA.
boundaries, while arrays of edge dislocations were observed in twist boundaries. In CL spectra, D-lines are observed in small angle tilt or twist boundaries. No luminescence related to grain boundaries was observed from the winding dislocation arrays in the 0.4° tilt boundaries. Broad luminescence was observed from the 6 tilt and 3° twist boundaries.
[4] K. Ikeda, T. Sekiguchi, S. Ito, M. Suezawa, Solid State Phenom. 63 – 64 (1998) 481. [5] N.A. Drozdov, A.A. Patrin, V.D. Tkachev, Pis’ma Zh. Eksp. Teor. Fiz. 23 (1976) 651 [JETP Lett. 23 597 (1976)]. [6] M. Suezawa, Y. Sasaki, K. Sumino, Phys. Status Solidi A 79 (1983) 173. [7] R. Sauer, J. Weber, J. Stolz, E.R. Weber, K.-H. Kusters, H. Alexander, Appl. Phys. A 36 (1985) 1. [8] Y.u. Lerikov, Y.u. Rebane, S. Ruvimov, D. Tarhin, A. Sitnikova, Y.u. Shreter, Mater. Sci. Forum 83 – 87 (1992) 1321. [9] K. Weronek, J. Weber, A. Hopner, F. Ernst, R. Buchner, M. Stefaniak, H. Alexander, Mater. Sci. Forum 83 – 87 (1992) 1315. [10] V. Higgs, E.C. Lightowlers, C.E. Norman, P.C. Kightley, Proc. 16th International Conference on Defects in Semiconductors, Materials Science Forum, 1992, 83 – 87, pp. 1309. [11] T. Sekiguchi, V.V. Kveder, K. Sumino, J. Appl. Phys. 76 (1995) 7882. [12] T. Sekiguchi, K. Sumino, J. Appl. Phys. 76 (1996) 3253. [13] T. Sekiguchi, K. Sumino, Rev. Sci. Instrum. 66 (1995) 4277. [14] K. Ikeda, T. Sekiguchi, S. Ito, M. Takebe, M. Suezawa, J. Crystal Growth 210 (2000) 90.
References [1] A.P. Sutton, R.W. Balluffi, Interfaces in Crystalline Materials, Oxford University Press, 1996. [2] U. Gosele, H. Stenzel, M. Reiche, T. Martini, H. Steinkirchner, Q.-Y. Tong, Solid State Phenom. 47 –48 (1996) 33. [3] M. Benamara, A. Rocher, P. Sopena, A. Claverie, A. Laporte, G. Sarrabayrouse, L. Lescouzeres, A. Peyre-Lavigne, Mat. Sci. Eng. B42 (1996) 164.