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Anti-phase domain boundaries in ZnGeP2 (ZGP)
Optical Materials 16 (2001) 119±123
www.elsevier.nl/locate/optmat
Anti-phase domain boundaries in ZnGeP2 (ZGP) Y. Shimony a,b,*, R. Fledman a, I. Dahan b, G. Kimmel b a b
Rotem Industries, Rotem Industrial Park, Mishor Yamin, D.N. Arava 86800, Israel Nuclear Research Center ± Negev (NRCN), P.O. Box 9001, Beer-Sheva 84190, Israel
Abstract Coherently oriented cubic defects were recently reported to exist within the tetragonal lattice of zinc±germanium± phosphide, ZnGeP2 (ZGP). X-ray diraction utilizing whole pattern optimization (Rietveld method) and line-pro®le®tting (LPF) enabled us to identify these defects. In the present research, transmission electron microscopy (TEM) was used for direct observation of these defects. The bright ®eld and dark ®eld TEM images of the ZGP foil indicate the existence of anti-phase domain boundaries (APB). Electron diraction patterns clearly reveal two coherently oriented entities, one of a tetragonal symmetry in accordance with the chalcopyrite lattice, the other however of a cubic symmetry. This con®rms our former ®nding of the existence of coherently oriented cubic defects in as-grown chalcopyrite ZGP crystal. Ó 2001 Elsevier Science B.V. All rights reserved.
1. Introduction A disordered zinc-blende structure was identi®ed within some of the ordered chalcopyrite crystals belonging to the ternary I±III±VI2 and II±IV±V2 groups [1]. In most cases, this phenomenon is also accompanied with a solid±solid structural phase transition, which occurs at elevated temperatures [2]. Binsma et al. [3] have found that an order±disorder transition occurs only for chalcopyrite crystals of an axial ratio c=a > 1:95. The ordered arrangement of the cation lattice of the chalcopyrites results in a tetragonal distortion d, de®ned by d 2 c=a. Order±disorder transition has already been found in ZnSnP2 , ZnGeP2 (ZGP), and CdSiP2 compounds [3]. In the case of ZnSnP2 , various degrees of ordering were obtained, depending on the cooling rate during the crystal growth [4]. This partly or*
Corresponding author.
dered crystal showed a mosaic structure, consisting of blocks, each having either the chalcopyrite or the zinc-blende structure [4]. In ZGP, the presence of a large number of zinc and germanium anti-sites is expected, since the material solidi®es at 1027°C as a zinc-blende random alloy, and undergoes a phase transition to the chalcopyrite structure at 952°C [5]. Because the kinetics of the order±disorder transition is sluggish, some residual disorder may remain after cooling to below the transition temperature. Recently, residual disorder was also observed in ZGP, by using X-ray diraction [6]. It should be emphasized here, however, that although order±disorder transition has already been found in ZGP long ago by utilizing dierential thermal analysis (DTA) [7], recent DTA measurements showed no such transition [8]. A wide optical absorption band near the band edge is usually found in ZGP crystals, which are grown either by the gradient freeze technique [9] or by the Czochralski method [10]. This band, extending from 0.7 to about 2.5 lm, is attributed to
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Y. Shimony et al. / Optical Materials 16 (2001) 119±123
photo-ionization of a native defect-related acceptor labeled AL1 [11]. It was suggested that AL1 primarily displays itself as a component of a native defect complex, possibly VZn VP (zinc and phosphorus vacancies, respectively) [11]. Recent studies con®rmed that the main defect in the meltgrown ZGP is VZn , while VP as the dominant donor exists in a highly compensated material [9]. The native point defects in the ZGP lattice have been already studied by various techniques such as by optical absorption [12], photoluminescence [13], EPR [14], ENDOR [15], and temperature-dependant Hall-eect [16]. Thermal annealing [17], electron beam, and c-ray irradiation [18] treatments were successfully applied on ZGP to reduce this parasitic optical absorption in as-grown crystal. Although correlation between the appearance of disordered cubic domains in melt grown ZGP crystals, to its residual absorption at the near-IR has already been con®rmed [19], 1 no direct observation of this structural defect has yet been demonstrated. In the present paper, we show our recent results on transmission electron microscopy (TEM) studies of ZGP. They provide the ®rst direct observation of the disordered structural defects in melt grown ZGP, and provide a better understanding of their nature.
2. Experimental ZGP single crystals for the present study were grown by horizontal gradient freezing [6]. Results obtained by powder X-ray diraction were analyzed by peak-by-peak line pro®le ®tting, and whole pattern optimization (Rietveld method). For the TEM studies, a round ZGP sample was drilled out of a 2 mm thickness wafer by using an ultrasonic cutter. The sample thickness was then reduced to about 100 lm by utilizing Gatan precision grinder model 602. A 2 mm diameter dimple was then made in the center of the ZGP sample, decreasing its thickness to 5±10 lm. Finally a hole was drilled at the dimple center by ion milling. A 1 For former results on the lattice parameters of ZGP, see also [20].
PHILIPS CM200 STEM system was used to examine the ZGP samples. 3. Results and discussion Fig. 1(a) shows an X-ray powder diraction pattern of a melt-grown ZGP crystal, which is apparently consistent with the chalcopyrite structure [5]. Rietveld re®nement of this pattern, however, yielded a ®nal agreement factor R 0:23, indicating poor ®tting. The ®t was signi®cantly improved by assuming that the crystal contents two constituents, one of the tetragonal chalcopyrite structure (assigned as a-ZGP), and the other of the zinc-blende cubic structure (assigned as bZGP). Both structures are related to each other by atet acub , and ctet 2acub , with a and c being the lattice parameters. As a result of the Rietveld re®nement, the R-factor was reduced to RB 0:02 for the a-phase, and to RB 0:10 for the b-phase. Based on the Rietveld re®nement, the patterns of a and b phases were calculated, and shown in Figs. 1(b) and (c), respectively. Similar results were obtained with X-ray diraction of crystalographically oriented ZGP single crystals, when the diraction patterns were treated with line pro®le ®tting. The diraction pattern of the cubic phase is always obtained with broadened lines. Details of the X-ray diraction analysis of melt-grown ZGP were recently published [19,20] 1. By using the TEM, small zones of irregularity were observed within the matrix of as-grown ZGP crystal. In Fig. 2(a) the bright-®eld (BF) of such a typical zone is depicted, at 11.5 K magni®cation. Fig. 2(b) shows the same defect at the same magni®cation in the dark ®eld (DF). These two ®gures look the same, however, with a reverse contrast. In Fig. 3 the same defect is shown at a magni®cation of 66 K in both the bright and dark ®elds, which are characterized by typical fringe patterns. Such fringe patterns (Fig. 3) might be attributed to either stacking faults, planar precipitates with small mis®t forms, bend contour, or anti-phase domain boundaries (APB) [21]. The possibility that a bend contour is responsible for the fringe pattern was excluded by a minute tilt of the sample, since this would cause the fringes to move. In addition,
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
121
Fig. 1. X-ray powder diraction patterns of melt-grown ZGP crystals: (a) The experimental pattern, also contains extra lines of germanium that was added for calibration (raw); (b) and (c) are the tetragonal and cubic diraction patterns, that were obtained by Riveted re®nement of pattern (a).
Fig. 2. Bright-®eld (BF) (a) and dark-®eld (DF) (b) TEM images of anti-phase domain boundary in ZGP (Mag. 11.5 K).
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Y. Shimony et al. / Optical Materials 16 (2001) 119±123
Fig. 3. BF (a) and DF (b) TEM images of anti-phase domain boundary in ZGP (Mag. 66 K), taken from the same area as in Fig. 2, respectively.
careful interpretation of the TEM patterns, Figs. 2 and 3, leads to the conclusion that it arises from an APB defect, as it meets the demands for the identi®cation of such a defect as APB [21]. Thus, it seems likely that the tetragonal matrix of ZGP contains an anti-phase domain boundary defect, also known as p-boundary [21]. Note that antiphase domain boundaries usually occur in ordered materials. This defect appears when there is a change in the identity of the atom at a given lattice point but there is no atomic stacking change like those that occur at a stacking-faults [21].
Fig. 4. Electron diraction pattern from the anti-phase domain boundary regime in ZGP. Two dierent structures can be observed within the pattern, coherently oriented with respect to each: a set of small dots corresponds to ordered tetragonal ZGP, and another set of spread dots which ®ts to disordered cubic ZGP. See text for details.
In order to examine how the APB relates to the residual cubic phase as obtained by the XRD [19,20] 1 electron diraction images were taken from the vicinity of these domains. In Fig. 4, a typical electron diraction pattern is presented. This pattern was recorded from the same area appearing in Fig. 2. Two sets of dots can be observed within the pattern, coherently oriented with respect to each other. One set contains small and sharp dots, the other set is characterized by spread dots. The ®rst set of sharp and small dots belongs to the tetragonal matrix of ZGP, since it ®ts well to the lattice parameters a 0:546 nm, and c 1:071 nm [19,20] 1. The second pattern with spread dots ®ts to a cubic phase having a lattice parameters of a 0:545 nm. Note that this result is in full agreement with our XRD results, including of the line broadening of the cubic phase. It thus turns out that these two structures de®nitely correspond to the ordered and disordered ZGP phases, respectively, which appear in Figs. 1(b) and (c). The zone axis of the electron diffraction patterns for both phases is h0 0 1i. Note that only in the h0 0 1i zone axis one can distinguish between the c- and a-axes of the ordered phase. The coherency between the two sets of electron diraction patterns (Fig. 4) indicates that the two crystalline entities are mutually oriented. This result is compatible with the identi®cation of the defect appearing in the TEM image as an APB. Similar phenomenon has already been observed at the phase transition between the NiAl and NiAl3 phases [22].
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
As already mentioned, the optical absorption band in the near IR in ZGP is commonly assigned to native point defects. Such defects in the cation sub-lattice may arise either from non-stoichiometric evaporation of the constituent elements at elevated temperatures, or from disordering which occurs during solidi®cation. In the present study, TEM and electron diraction results reveal the appearance of anti-phase domain boundaries (APB) in the ordered ZGP matrix. It should be borne in mind, however, that such boundaries are often associated with a variety of point defects, such as anti-site pairs, and vacancies. Thus, we tend to believe that the anti-phase domain boundaries revealed by the TEM and electron diraction study is related to the creation of various point defects in ZGP. 4. Summary Transmission electron microscopy and electron diraction was used for direct observation of antiphase domain boundaries in chalcopyrite ZGP. The structural defect thus observed correlates to our former results, based on X-ray diraction, on the existence of a cubic structure embedded within the tetragonal matrix of ZGP. The anti-phase domain boundaries are coherently oriented relative to the tetragonal matrix, and might be associated with various point defects, which have already been found to exist in melt-grown ZGP. References [1] A.A. Viapolin, E.O. Osmanov, V.D. Prochukhan, Izv. Acad. Nauk SSSR, Neorg. Mater. 8 (5) (1972) 947. [2] L. Shay, J.H. Wernick, in: Ternary Chalcopyrite Semiconductors Growth Electronic Properties and Applications, Pergamon Press, New York, 1975. [3] J.J.M. Binsma, L.J. Giling, J. Bloem, Phys. Stat. Sol. (a) 63 (1981) 595. [4] A.A. Vaipolin, N.A. Goryunova, L.I. Kleshchinskii, G.V. Loshakova, E.O. Osmanov, Phys. Stat. Sol. 29 (1968) 435.
123
[5] M.H. Rakowsky, W.K. Kuhn, W.J. Lauderdale, L.E. Halliburton, G.J. Edwards, M.P. Scripsick, P.G. Schunemann, T.M. Pollak, M.C. Ohmer, F.K. Hopkins, Appl. Phys. Lett. 64 (13) (1994) 1615. [6] Y. Shimony, G. Kimmel, O. Raz, M.P. Dariel, J. Cryst. Growth 198±199 (1999) 583. [7] K. Masumoto, S. Isomura, W. Goto, J. Phys. Chem. Solids 27 (1966) 1939. [8] S. Fiechter, R.H. Castleberry, M. Angelov, K.J. Bachmann, in: M.O. Manasreh, T.M. Myers, F.H. Julien (Eds.), Infrared Applications of Semiconductors ± Materials, Processing and Devices, MRS Symposium Proceedings, vol. 450, MRS 1996 Fall Meeting, Boston, 2±6 December 1996, p. 315. [9] F.K. Hopkins, Laser Focus World, July 1995, p. 87. [10] D.F. Bliss, M. Harris, J. Horrigan, W.M. Higgins, A. Armington, J.A. Adamski, J. Cryst. Growth 137 (1994) 1945. [11] H.M. Hobgood, T. Henningsen, R.N. Thomas, R.H. Hopkins, M.C. Ohmer, W.C. Mitchel, D.W. Fischer, S.M. Hedge, F.K. Hopkins, J. Appl. Phys. 73 (8) (1993) 4030. [12] L.S. Gorbon, V.V. Grishchuk, I.J. Tregub, Sov. Phys. Semicond. 18 (1984) 567. [13] G.K. Averkieva, V.S. Grigoreva, I.A. Maltseva, V.D. Prochukhan, Yu.V. Rud, Phys. Status. Solidi A 39 (1977) 453. [14] M.H. Rakowsky, W.K. Kuhn, W.J. Lauderdale, L.E. Halliburton, G.J. Edwards, M.P. Scripsick, P.G. Schunemann, T.M. Pollak, M.C. Ohmer, F.K. Hopkins, Appl. Phys. Lett. 64 (13) (1994) 1615. [15] L.E. Hallliburton, G.J. Edwards, M.P. Scripsick, M.H. Rakowsky, P.G. Schunemann, T.M. Pollak, Appl. Phys. Lett. 66 (1995) 2670. [16] A. Sodeika, A.Z. Silevicius, Z. Januskevicius, A. Sakalas, Phys. Status Solidi A 69 (1982) 491. [17] Y.V. Rud, R.V. Mesagutova, Sov. Tech. Phys. Lett. 7 (2) (1981) 72. [18] M.H. Rakowsky, W.J. Lauderdale, R.A. Mantz, R. Pandey, P.J. Drevinsky, D.C. Jacobson, D.E. Luzzi, T.F. Heinz, M. Iwaki (Eds.), Beam±Solid Interactions for Materials Synthesis and Characterization Symposium, Pittsburgh, PA, USA, 1995, p. 735. [19] Y. Shimony, O. Raz, G. Kimmel, M.P. Dariel, Opt. Mater. 13 (1) (1999) 101. [20] M.D. Lind, R.W. Grant, J. Chem. Phys. 58 (1) (1973) 357 JCPDS No. 33-1471. [21] J.W. Edington, Practical Electron Microscopy in Material Science, Van Nostrand Reinhold Company, New York, 1976. [22] B.W. Williams, C.B. Carter, Transmission Electron Microscopy, Plenum Press, New York, 1996.
www.elsevier.nl/locate/optmat
Anti-phase domain boundaries in ZnGeP2 (ZGP) Y. Shimony a,b,*, R. Fledman a, I. Dahan b, G. Kimmel b a b
Rotem Industries, Rotem Industrial Park, Mishor Yamin, D.N. Arava 86800, Israel Nuclear Research Center ± Negev (NRCN), P.O. Box 9001, Beer-Sheva 84190, Israel
Abstract Coherently oriented cubic defects were recently reported to exist within the tetragonal lattice of zinc±germanium± phosphide, ZnGeP2 (ZGP). X-ray diraction utilizing whole pattern optimization (Rietveld method) and line-pro®le®tting (LPF) enabled us to identify these defects. In the present research, transmission electron microscopy (TEM) was used for direct observation of these defects. The bright ®eld and dark ®eld TEM images of the ZGP foil indicate the existence of anti-phase domain boundaries (APB). Electron diraction patterns clearly reveal two coherently oriented entities, one of a tetragonal symmetry in accordance with the chalcopyrite lattice, the other however of a cubic symmetry. This con®rms our former ®nding of the existence of coherently oriented cubic defects in as-grown chalcopyrite ZGP crystal. Ó 2001 Elsevier Science B.V. All rights reserved.
1. Introduction A disordered zinc-blende structure was identi®ed within some of the ordered chalcopyrite crystals belonging to the ternary I±III±VI2 and II±IV±V2 groups [1]. In most cases, this phenomenon is also accompanied with a solid±solid structural phase transition, which occurs at elevated temperatures [2]. Binsma et al. [3] have found that an order±disorder transition occurs only for chalcopyrite crystals of an axial ratio c=a > 1:95. The ordered arrangement of the cation lattice of the chalcopyrites results in a tetragonal distortion d, de®ned by d 2 c=a. Order±disorder transition has already been found in ZnSnP2 , ZnGeP2 (ZGP), and CdSiP2 compounds [3]. In the case of ZnSnP2 , various degrees of ordering were obtained, depending on the cooling rate during the crystal growth [4]. This partly or*
Corresponding author.
dered crystal showed a mosaic structure, consisting of blocks, each having either the chalcopyrite or the zinc-blende structure [4]. In ZGP, the presence of a large number of zinc and germanium anti-sites is expected, since the material solidi®es at 1027°C as a zinc-blende random alloy, and undergoes a phase transition to the chalcopyrite structure at 952°C [5]. Because the kinetics of the order±disorder transition is sluggish, some residual disorder may remain after cooling to below the transition temperature. Recently, residual disorder was also observed in ZGP, by using X-ray diraction [6]. It should be emphasized here, however, that although order±disorder transition has already been found in ZGP long ago by utilizing dierential thermal analysis (DTA) [7], recent DTA measurements showed no such transition [8]. A wide optical absorption band near the band edge is usually found in ZGP crystals, which are grown either by the gradient freeze technique [9] or by the Czochralski method [10]. This band, extending from 0.7 to about 2.5 lm, is attributed to
0925-3467/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 5 - 3 4 6 7 ( 0 0 ) 0 0 0 6 7 - 7
120
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
photo-ionization of a native defect-related acceptor labeled AL1 [11]. It was suggested that AL1 primarily displays itself as a component of a native defect complex, possibly VZn VP (zinc and phosphorus vacancies, respectively) [11]. Recent studies con®rmed that the main defect in the meltgrown ZGP is VZn , while VP as the dominant donor exists in a highly compensated material [9]. The native point defects in the ZGP lattice have been already studied by various techniques such as by optical absorption [12], photoluminescence [13], EPR [14], ENDOR [15], and temperature-dependant Hall-eect [16]. Thermal annealing [17], electron beam, and c-ray irradiation [18] treatments were successfully applied on ZGP to reduce this parasitic optical absorption in as-grown crystal. Although correlation between the appearance of disordered cubic domains in melt grown ZGP crystals, to its residual absorption at the near-IR has already been con®rmed [19], 1 no direct observation of this structural defect has yet been demonstrated. In the present paper, we show our recent results on transmission electron microscopy (TEM) studies of ZGP. They provide the ®rst direct observation of the disordered structural defects in melt grown ZGP, and provide a better understanding of their nature.
2. Experimental ZGP single crystals for the present study were grown by horizontal gradient freezing [6]. Results obtained by powder X-ray diraction were analyzed by peak-by-peak line pro®le ®tting, and whole pattern optimization (Rietveld method). For the TEM studies, a round ZGP sample was drilled out of a 2 mm thickness wafer by using an ultrasonic cutter. The sample thickness was then reduced to about 100 lm by utilizing Gatan precision grinder model 602. A 2 mm diameter dimple was then made in the center of the ZGP sample, decreasing its thickness to 5±10 lm. Finally a hole was drilled at the dimple center by ion milling. A 1 For former results on the lattice parameters of ZGP, see also [20].
PHILIPS CM200 STEM system was used to examine the ZGP samples. 3. Results and discussion Fig. 1(a) shows an X-ray powder diraction pattern of a melt-grown ZGP crystal, which is apparently consistent with the chalcopyrite structure [5]. Rietveld re®nement of this pattern, however, yielded a ®nal agreement factor R 0:23, indicating poor ®tting. The ®t was signi®cantly improved by assuming that the crystal contents two constituents, one of the tetragonal chalcopyrite structure (assigned as a-ZGP), and the other of the zinc-blende cubic structure (assigned as bZGP). Both structures are related to each other by atet acub , and ctet 2acub , with a and c being the lattice parameters. As a result of the Rietveld re®nement, the R-factor was reduced to RB 0:02 for the a-phase, and to RB 0:10 for the b-phase. Based on the Rietveld re®nement, the patterns of a and b phases were calculated, and shown in Figs. 1(b) and (c), respectively. Similar results were obtained with X-ray diraction of crystalographically oriented ZGP single crystals, when the diraction patterns were treated with line pro®le ®tting. The diraction pattern of the cubic phase is always obtained with broadened lines. Details of the X-ray diraction analysis of melt-grown ZGP were recently published [19,20] 1. By using the TEM, small zones of irregularity were observed within the matrix of as-grown ZGP crystal. In Fig. 2(a) the bright-®eld (BF) of such a typical zone is depicted, at 11.5 K magni®cation. Fig. 2(b) shows the same defect at the same magni®cation in the dark ®eld (DF). These two ®gures look the same, however, with a reverse contrast. In Fig. 3 the same defect is shown at a magni®cation of 66 K in both the bright and dark ®elds, which are characterized by typical fringe patterns. Such fringe patterns (Fig. 3) might be attributed to either stacking faults, planar precipitates with small mis®t forms, bend contour, or anti-phase domain boundaries (APB) [21]. The possibility that a bend contour is responsible for the fringe pattern was excluded by a minute tilt of the sample, since this would cause the fringes to move. In addition,
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
121
Fig. 1. X-ray powder diraction patterns of melt-grown ZGP crystals: (a) The experimental pattern, also contains extra lines of germanium that was added for calibration (raw); (b) and (c) are the tetragonal and cubic diraction patterns, that were obtained by Riveted re®nement of pattern (a).
Fig. 2. Bright-®eld (BF) (a) and dark-®eld (DF) (b) TEM images of anti-phase domain boundary in ZGP (Mag. 11.5 K).
122
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
Fig. 3. BF (a) and DF (b) TEM images of anti-phase domain boundary in ZGP (Mag. 66 K), taken from the same area as in Fig. 2, respectively.
careful interpretation of the TEM patterns, Figs. 2 and 3, leads to the conclusion that it arises from an APB defect, as it meets the demands for the identi®cation of such a defect as APB [21]. Thus, it seems likely that the tetragonal matrix of ZGP contains an anti-phase domain boundary defect, also known as p-boundary [21]. Note that antiphase domain boundaries usually occur in ordered materials. This defect appears when there is a change in the identity of the atom at a given lattice point but there is no atomic stacking change like those that occur at a stacking-faults [21].
Fig. 4. Electron diraction pattern from the anti-phase domain boundary regime in ZGP. Two dierent structures can be observed within the pattern, coherently oriented with respect to each: a set of small dots corresponds to ordered tetragonal ZGP, and another set of spread dots which ®ts to disordered cubic ZGP. See text for details.
In order to examine how the APB relates to the residual cubic phase as obtained by the XRD [19,20] 1 electron diraction images were taken from the vicinity of these domains. In Fig. 4, a typical electron diraction pattern is presented. This pattern was recorded from the same area appearing in Fig. 2. Two sets of dots can be observed within the pattern, coherently oriented with respect to each other. One set contains small and sharp dots, the other set is characterized by spread dots. The ®rst set of sharp and small dots belongs to the tetragonal matrix of ZGP, since it ®ts well to the lattice parameters a 0:546 nm, and c 1:071 nm [19,20] 1. The second pattern with spread dots ®ts to a cubic phase having a lattice parameters of a 0:545 nm. Note that this result is in full agreement with our XRD results, including of the line broadening of the cubic phase. It thus turns out that these two structures de®nitely correspond to the ordered and disordered ZGP phases, respectively, which appear in Figs. 1(b) and (c). The zone axis of the electron diffraction patterns for both phases is h0 0 1i. Note that only in the h0 0 1i zone axis one can distinguish between the c- and a-axes of the ordered phase. The coherency between the two sets of electron diraction patterns (Fig. 4) indicates that the two crystalline entities are mutually oriented. This result is compatible with the identi®cation of the defect appearing in the TEM image as an APB. Similar phenomenon has already been observed at the phase transition between the NiAl and NiAl3 phases [22].
Y. Shimony et al. / Optical Materials 16 (2001) 119±123
As already mentioned, the optical absorption band in the near IR in ZGP is commonly assigned to native point defects. Such defects in the cation sub-lattice may arise either from non-stoichiometric evaporation of the constituent elements at elevated temperatures, or from disordering which occurs during solidi®cation. In the present study, TEM and electron diraction results reveal the appearance of anti-phase domain boundaries (APB) in the ordered ZGP matrix. It should be borne in mind, however, that such boundaries are often associated with a variety of point defects, such as anti-site pairs, and vacancies. Thus, we tend to believe that the anti-phase domain boundaries revealed by the TEM and electron diraction study is related to the creation of various point defects in ZGP. 4. Summary Transmission electron microscopy and electron diraction was used for direct observation of antiphase domain boundaries in chalcopyrite ZGP. The structural defect thus observed correlates to our former results, based on X-ray diraction, on the existence of a cubic structure embedded within the tetragonal matrix of ZGP. The anti-phase domain boundaries are coherently oriented relative to the tetragonal matrix, and might be associated with various point defects, which have already been found to exist in melt-grown ZGP. References [1] A.A. Viapolin, E.O. Osmanov, V.D. Prochukhan, Izv. Acad. Nauk SSSR, Neorg. Mater. 8 (5) (1972) 947. [2] L. Shay, J.H. Wernick, in: Ternary Chalcopyrite Semiconductors Growth Electronic Properties and Applications, Pergamon Press, New York, 1975. [3] J.J.M. Binsma, L.J. Giling, J. Bloem, Phys. Stat. Sol. (a) 63 (1981) 595. [4] A.A. Vaipolin, N.A. Goryunova, L.I. Kleshchinskii, G.V. Loshakova, E.O. Osmanov, Phys. Stat. Sol. 29 (1968) 435.
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[5] M.H. Rakowsky, W.K. Kuhn, W.J. Lauderdale, L.E. Halliburton, G.J. Edwards, M.P. Scripsick, P.G. Schunemann, T.M. Pollak, M.C. Ohmer, F.K. Hopkins, Appl. Phys. Lett. 64 (13) (1994) 1615. [6] Y. Shimony, G. Kimmel, O. Raz, M.P. Dariel, J. Cryst. Growth 198±199 (1999) 583. [7] K. Masumoto, S. Isomura, W. Goto, J. Phys. Chem. Solids 27 (1966) 1939. [8] S. Fiechter, R.H. Castleberry, M. Angelov, K.J. Bachmann, in: M.O. Manasreh, T.M. Myers, F.H. Julien (Eds.), Infrared Applications of Semiconductors ± Materials, Processing and Devices, MRS Symposium Proceedings, vol. 450, MRS 1996 Fall Meeting, Boston, 2±6 December 1996, p. 315. [9] F.K. Hopkins, Laser Focus World, July 1995, p. 87. [10] D.F. Bliss, M. Harris, J. Horrigan, W.M. Higgins, A. Armington, J.A. Adamski, J. Cryst. Growth 137 (1994) 1945. [11] H.M. Hobgood, T. Henningsen, R.N. Thomas, R.H. Hopkins, M.C. Ohmer, W.C. Mitchel, D.W. Fischer, S.M. Hedge, F.K. Hopkins, J. Appl. Phys. 73 (8) (1993) 4030. [12] L.S. Gorbon, V.V. Grishchuk, I.J. Tregub, Sov. Phys. Semicond. 18 (1984) 567. [13] G.K. Averkieva, V.S. Grigoreva, I.A. Maltseva, V.D. Prochukhan, Yu.V. Rud, Phys. Status. Solidi A 39 (1977) 453. [14] M.H. Rakowsky, W.K. Kuhn, W.J. Lauderdale, L.E. Halliburton, G.J. Edwards, M.P. Scripsick, P.G. Schunemann, T.M. Pollak, M.C. Ohmer, F.K. Hopkins, Appl. Phys. Lett. 64 (13) (1994) 1615. [15] L.E. Hallliburton, G.J. Edwards, M.P. Scripsick, M.H. Rakowsky, P.G. Schunemann, T.M. Pollak, Appl. Phys. Lett. 66 (1995) 2670. [16] A. Sodeika, A.Z. Silevicius, Z. Januskevicius, A. Sakalas, Phys. Status Solidi A 69 (1982) 491. [17] Y.V. Rud, R.V. Mesagutova, Sov. Tech. Phys. Lett. 7 (2) (1981) 72. [18] M.H. Rakowsky, W.J. Lauderdale, R.A. Mantz, R. Pandey, P.J. Drevinsky, D.C. Jacobson, D.E. Luzzi, T.F. Heinz, M. Iwaki (Eds.), Beam±Solid Interactions for Materials Synthesis and Characterization Symposium, Pittsburgh, PA, USA, 1995, p. 735. [19] Y. Shimony, O. Raz, G. Kimmel, M.P. Dariel, Opt. Mater. 13 (1) (1999) 101. [20] M.D. Lind, R.W. Grant, J. Chem. Phys. 58 (1) (1973) 357 JCPDS No. 33-1471. [21] J.W. Edington, Practical Electron Microscopy in Material Science, Van Nostrand Reinhold Company, New York, 1976. [22] B.W. Williams, C.B. Carter, Transmission Electron Microscopy, Plenum Press, New York, 1996.