Abstract

We report laser-induced crystallization behavior of binary Sb–Te and ternary Ge-doped eutectic Sb70Te30 thin film samples in a typical quadrilayer stack as used in phase-change optical disk data storage. Several experiments have been conducted on a two-laser static tester in which one laser operating in pulse mode writes crystalline marks on amorphous film or amorphous marks on crystalline film, while the second laser operating at low-power cw mode simultaneously monitors the progress of the crystalline or amorphous mark formation in real time in terms of the reflectivity variation. The results of this study show that the crystallization kinetics of this class of film is strongly growth dominant, which is significantly different from the crystallization kinetics of stochiometric Ge–Sb–Te compositions. In Sb–Te and Ge-doped eutectic Sb70Te30 thin-film samples, the crystallization behavior of the two forms of amorphous states, namely, as-deposited amorphous state and melt-quenched amorphous state, remains approximately same. We have also presented experiments showing the effect of the variation of the Sb/Te ratio and Ge doping on the crystallization behavior of these films.

© 2002 Optical Society of America

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References

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  1. N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
    [CrossRef]
  2. H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
    [CrossRef]
  3. G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
    [CrossRef]
  4. M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
    [CrossRef]
  5. P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
    [CrossRef]
  6. E. M. Wright, P. K. Khulbe, M. Mansuripur, “Dynamic theory of crystallization in Ge2Sb2.3Te5 phase-change optical recording media,” Appl. Opt. 39, 6695–6701 (2000).
    [CrossRef]
  7. M. Mansuripur, J. K. Erwin, W. Bletscher, P. Khulbe, K. Sadeghi, X. Xun, A. Gupta, S. Mendis, “Static tester for characterization of phase-change, dye-polymer, and magneto-optic media of optical data storage,” Appl. Opt. 38, 7095–7104 (1999).
    [CrossRef]
  8. N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
    [CrossRef]
  9. P. K. Khulbe, M. Mansuripur, “Temperature-dependence of optical constants in phase-change media,” Technical Digest, Optical Data Storage Topical Meeting 2001, 121–123 (2001).
  10. TEMPROFILE™, a product of MM Research, Inc., Tucson, Ariz.
  11. J. W. Christian, The Theory of Transformations in Metals and Alloys, 2nd ed. (Pergamon, Oxford, 1975).

2000 (2)

P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
[CrossRef]

E. M. Wright, P. K. Khulbe, M. Mansuripur, “Dynamic theory of crystallization in Ge2Sb2.3Te5 phase-change optical recording media,” Appl. Opt. 39, 6695–6701 (2000).
[CrossRef]

1999 (1)

1993 (1)

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

1991 (1)

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

Akahira, N.

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

Bletscher, W.

Borg, H. J.

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

Christian, J. W.

J. W. Christian, The Theory of Transformations in Metals and Alloys, 2nd ed. (Pergamon, Oxford, 1975).

Deguchi, H.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Erwin, J. K.

Gupta, A.

Harigaya, M.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Hashizume, T.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Horie, M.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Horikx, J. J. L.

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

Ide, Y.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Iwasaki, H.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Kageyama, Y.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Khulbe, P.

Khulbe, P. K.

E. M. Wright, P. K. Khulbe, M. Mansuripur, “Dynamic theory of crystallization in Ge2Sb2.3Te5 phase-change optical recording media,” Appl. Opt. 39, 6695–6701 (2000).
[CrossRef]

P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
[CrossRef]

P. K. Khulbe, M. Mansuripur, “Temperature-dependence of optical constants in phase-change media,” Technical Digest, Optical Data Storage Topical Meeting 2001, 121–123 (2001).

Kiyano, K.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Lankhorst, M. H. R.

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

Mansuripur, M.

P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
[CrossRef]

E. M. Wright, P. K. Khulbe, M. Mansuripur, “Dynamic theory of crystallization in Ge2Sb2.3Te5 phase-change optical recording media,” Appl. Opt. 39, 6695–6701 (2000).
[CrossRef]

M. Mansuripur, J. K. Erwin, W. Bletscher, P. Khulbe, K. Sadeghi, X. Xun, A. Gupta, S. Mendis, “Static tester for characterization of phase-change, dye-polymer, and magneto-optic media of optical data storage,” Appl. Opt. 38, 7095–7104 (1999).
[CrossRef]

P. K. Khulbe, M. Mansuripur, “Temperature-dependence of optical constants in phase-change media,” Technical Digest, Optical Data Storage Topical Meeting 2001, 121–123 (2001).

Mendis, S.

Miyagawa, N.

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

Mizuno, M.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Nishiuchi, K.

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

Nobukuni, N.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Nonoyama, O.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Ohano, T.

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

Ohno, E.

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

Rijper, J. C. N.

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

Sadeghi, K.

Sakaue, Y.

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

Takahashi, M.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Wright, E. M.

E. M. Wright, P. K. Khulbe, M. Mansuripur, “Dynamic theory of crystallization in Ge2Sb2.3Te5 phase-change optical recording media,” Appl. Opt. 39, 6695–6701 (2000).
[CrossRef]

P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
[CrossRef]

Xun, X.

Yamada, K.

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Yamada, N.

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

Zhou, G. F.

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

Appl. Opt. (2)

J. Appl. Phys. (2)

N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, “Rapid-phase transition of GeTesngbnd;Sb2Te3 pseudobinary amorphous films for optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
[CrossRef]

P. K. Khulbe, E. M. Wright, M. Mansuripur, “Crystallization behavior of as-deposited, melt-quenched, and primed amorphous states of Ge2Sb2.3Te5 films,” J. Appl. Phys. 88, 3926–3933 (2000).
[CrossRef]

Jpn. J. Appl. Phys. (1)

H. Iwasaki, M. Harigaya, O. Nonoyama, Y. Kageyama, M. Takahashi, K. Yamada, H. Deguchi, Y. Ide, “Completely erasable phase change optical disk II: Application of Ag-In-Sb-Te mixed-phase system for rewritable compact disc compatible with CD-velocity and double CD-velocity,” Jpn. J. Appl. Phys. 32, 5241–5247 (1993).
[CrossRef]

Other (6)

G. F. Zhou, H. J. Borg, J. C. N. Rijper, M. H. R. Lankhorst, J. J. L. Horikx, “Crystallization behavior of phase change materials: comparison between nucleation- and growth-dominated crystallization,” in Optical Data Storage 2000, D. G. Stinson, R. Katayma, Proc. SPIE4090, 108–117 (2000).
[CrossRef]

M. Horie, T. Ohano, N. Nobukuni, K. Kiyano, T. Hashizume, M. Mizuno, “Material characterization and application of eutectic SbTe based phase-change optical recording media,” in Optical Data Storage 2001, T. Hurst, S. Kobayashi, eds., Proc. SPIE4342, 76–87 (2002).
[CrossRef]

N. Akahira, N. Miyagawa, K. Nishiuchi, Y. Sakaue, E. Ohno, “High-density recording on phase-change optical disks,” in Optical Data Storage ’95, G. R. Knight, H. Ooci, X.-S. Tyan, Proc. SPIE 2514, 294–302 (1995).
[CrossRef]

P. K. Khulbe, M. Mansuripur, “Temperature-dependence of optical constants in phase-change media,” Technical Digest, Optical Data Storage Topical Meeting 2001, 121–123 (2001).

TEMPROFILE™, a product of MM Research, Inc., Tucson, Ariz.

J. W. Christian, The Theory of Transformations in Metals and Alloys, 2nd ed. (Pergamon, Oxford, 1975).

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Figures (14)

Fig. 1
Fig. 1

Typical quadrilayer PC optical disk used in the present study. Two laser beams are focused on the PC layer at the same spot from the substrate side. One laser is pulsed, while the other, operating in cw mode, monitors in real time the reflectivity variation caused by pulse laser heating.

Fig. 2
Fig. 2

Ten reflectivity traces obtained during crystalline mark formation on as-deposited Ge5Sb68Te27 film in a quadrilayer structure. All crystalline marks were written by 3.0-mW laser pulses. The pulse duration was 300 ms (0–300 ms along the x axis). Reflectivity variation is monitored by 0.2-mW cw laser beam from the second laser.

Fig. 3
Fig. 3

Probability of crystallization versus irradiation time for various 4.0-mW laser-pulse schemes. In the case of irradiation from multiple pulses, the time interval in between pulses is a few seconds and is not counted in the total irradiation time.

Fig. 4
Fig. 4

Picture showing as-deposited amorphous, melt-quenched amorphous, and crystalline sections on a Ge5Sb68Te27 film. The crystalline section was prepared by x–y scanning of a cw laser beam focused on an as-deposited amorphous surface. The melt-quenched amorphous area is created by writing an array (40 × 80) of closely spaced melt-quenched amorphous marks on a crystalline film surface. Focused laser pulses of 16.0 mW and 40-ns long wrote individual melt-quenched marks. The mark spacing in the array is 0.5 µm. We also see some defects on the film, which might have occurred during deposition.

Fig. 5
Fig. 5

Reflectivity variation across the film surface shown in Fig. 4. Reflectivity variation was measured by a focused cw laser beam operating at very low power. This graph indicates that the reflectivity of the melt-quenched amorphous state is slightly higher than the as-deposited amorphous state.

Fig. 6
Fig. 6

Reflectivity traces obtained during crystalline mark formation in melt-quenched Ge5Sb68Te27 film in a quadrilayer structure. All crystalline marks were written by a single 3.0-mW laser pulse. The pulse duration was 300 ms (0–300 ms along the x axis). A 0.2-mW cw laser beam from the second laser monitors the reflectivity variation.

Fig. 7
Fig. 7

Probability of crystallization versus irradiation time for various 4.0-mW laser-pulse schemes. In the case of irradiation from multiple pulses, the time interval in between pulses is a few seconds and is not counted in the total irradiation time.

Fig. 8
Fig. 8

Schematic of a crystallization experiment conducted at the boundary of the as-deposited amorphous and crystalline Ge5Sb68Te27 film. Open circles indicate laser spots that have a different overlap with the amorphous and crystalline sections as we move along the line AB. The reflectivity curves obtained on application of 4.0-mW, 5.0-µs long laser pulses along this line are also shown. The bottom curve is obtained from spot A, which is in the fully as-deposited amorphous section, and the top curve is obtained from spot B, which is in the fully crystalline section.

Fig. 9
Fig. 9

Schematic of a crystallization experiment conducted at the boundary of the melt-quenched amorphous and crystalline Ge5Sb68Te27 film. Open circles indicate laser spots, which have a different overlap with the amorphous and crystalline sections as we move along the line AB. The reflectivity curves obtained on application of 4.0-mW and 5.0-µs long laser pulses along this line are also shown. The bottom curve is obtained from spot A, which is in the fully melt-quenched amorphous section, and the top curve is obtained from spot B, which is in the fully crystalline section.

Fig. 10
Fig. 10

(a) Reflectivity curves obtained during melt-quenched amorphous mark formation on a fully crystalline Ge5Sb68Te27 film by a 16-mW, 40-ns long laser pulse and during the attempted erasure of this mark at various laser pulse powers. All laser pulses used in the erasure have a 2.0-µs pulse width. (b) Reflectivity curves obtained during melt-quenched amorphous mark formation on fully crystalline Ge5Sb68Te27 film by a 14.5-mW, 40-ns long laser pulse and during the attempted erasure of this mark at various laser pulse powers. All laser pulses used in the erasure have a 2.0-µs pulse width. (c) Reflectivity curves obtained during melt-quenched amorphous mark formation on a fully crystalline Ge5Sb68Te27 film by a 12-mW, 40-ns long laser pulse and during the attempted erasure of this mark at various laser pulse powers. All laser pulses used in the erasure have a 2.0-µs pulse width.

Fig. 11
Fig. 11

Reflectivity trace obtained during a melt-quenched amorphous mark formation by a 14.5-mW, 40-ms laser pulse shows a drop in reflectivity from 34% to 25%. If we erase many such melt-quenched marks by 4.3-mW, 2.0-µs long pulses, we obtain the reflectivity variation curves as shown.

Fig. 12
Fig. 12

Variation in the reflected signal during the erasure of various size melt-quenched amorphous marks in (a) eutectic Ge5Sb68Te27 alloy film and (b) stochiometric Ge-Sb-Te alloy film. Various size amorphous marks were created on crystalline films by 40-ns long laser pulses at various pulse powers as indicated. These melt-quenched amorphous marks were erased by slowly increasing the cw power of laser 1, while laser 2 operating at a fixed low cw power (0.1 mW) was used for measuring the reflected signal.

Fig. 13
Fig. 13

(a) Probability of crystalline mark formation versus the duration of the pulses at various laser pulse power in sample Sb86.7Te13.3. (b) Crystallization growth rate (or speed of crystalline mark formation) at various laser pulse power in sample Sb86.7Te13.3. Amorphous and crystalline state reflectivities are scaled in the range 0 to 1.

Fig. 14
Fig. 14

Comparison of the variation in (a) nucleation time and (b) crystalline growth rate as a function of the Sb/Te ratio in binary and ternary alloys.

Tables (1)

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Table 1 Description of Samples Useda

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