Abstract

We present the results of crystallization and amorphization studies on a thin-film sample of Ge2Sb2.3Te5, encapsulated in a quadrilayer stack as in the media of phase-change optical disk data storage. The study was conducted on a two-laser static tester in which one laser, operating in pulsed mode, writes either amorphous marks on a crystalline film or crystalline marks on an amorphous film. The second laser, operating at low power in the cw mode, simultaneously monitors the progress of mark formation in terms of the variations of reflectivity both during the write pulse and in the subsequent cooling period. In addition to investigating some of the expected features associated with crystallization and amorphization, we noted certain curious phenomena during the mark-formation process. For example, at low-power pulsed illumination, which is insufficient to trigger the phase transition, there is a slight change in the reflectivity of the sample. This is believed to be caused by a reversible change in the complex refractive index of the Ge2Sb2.3Te5 film in the course of heating above the ambient temperature. We also observed that the mark-formation process may continue for as long as 1 µs beyond the end of the write laser pulse. This effect is especially pronounced during amorphous mark formation under high-power, long-pulse illumination.

© 2000 Optical Society of America

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  1. T. Ide, M. Okada, “Jitter improvement in mark edge recording for phase-change optical disk with optical phase encoding,” Appl. Phys. Lett. 64, 1613–1614 (1994).
    [CrossRef]
  2. C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
    [CrossRef]
  3. J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
    [CrossRef]
  4. T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
    [CrossRef]
  5. K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
    [CrossRef]
  6. N. Yamada, E. Ohno, K. Nishiuchi, N. Akahira, M. Takao, “Rapid-phase transition of GeTe-Sb2Te3 pseudobinary amorphous thin films for an optical disk memory,” J. Appl. Phys. 69, 2849–2856 (1991).
    [CrossRef]
  7. M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
    [CrossRef]
  8. M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
    [CrossRef]
  9. M. Mansuripur, J. K. Erwin, W. Bletscher, P. Khulbe, K. Sadeghi, X. Xun, A. Gupta, S. B. Mendes, “Static tester for characterization of phase-change, dye-polymer, and magneto-optical media for optical data storage,” Appl. Opt. 38, 7095–7104 (1999).
    [CrossRef]
  10. T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).
  11. T. Ohta, “Study of phase-change optical disk memory,” Ph.D. dissertation (Osaka Prefecture University, Osaka, Japan, 1995).
  12. TEMPROFILE is a product of MM Research Inc., Tucson, Arizona. The theoretical basis of the program is described in M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Laser-induced local heating of multilayers,” Appl. Opt. 21, 1106–1114 (1982) and in M. Mansuripur, G. A. N. Connell, “Laser-induced local heating of moving multilayer media,” Appl. Opt. 22, 666–670 (1983).

1999 (1)

1998 (1)

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

1997 (1)

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
[CrossRef]

1995 (2)

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

1994 (1)

T. Ide, M. Okada, “Jitter improvement in mark edge recording for phase-change optical disk with optical phase encoding,” Appl. Phys. Lett. 64, 1613–1614 (1994).
[CrossRef]

1992 (1)

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

1991 (1)

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

1986 (1)

M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
[CrossRef]

1985 (1)

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Akahira, N.

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

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

Akutagawa, R.

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

Barton, R.

M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
[CrossRef]

Bletscher, W.

Chen, M.

M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
[CrossRef]

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Coombs, J. H.

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

Erwin, J. K.

Gerber, U. G.

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Gupta, A.

Ide, T.

T. Ide, M. Okada, “Jitter improvement in mark edge recording for phase-change optical disk with optical phase encoding,” Appl. Phys. Lett. 64, 1613–1614 (1994).
[CrossRef]

Imanaka, R.

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

Jacobs, B. A. J.

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

Jipson, V. B.

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Jongenelis, A. P. J. M.

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

Khulbe, P.

Kim, S. G.

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
[CrossRef]

Kim, W. M.

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
[CrossRef]

Mansuripur, M.

Marrello, V.

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Mendes, S. B.

Nagata, K.

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

Nishiuchi, K.

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

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

Ohara, S.

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

Ohno, E.

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

Ohta, T.

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

T. Ohta, “Study of phase-change optical disk memory,” Ph.D. dissertation (Osaka Prefecture University, Osaka, Japan, 1995).

Okada, M.

T. Ide, M. Okada, “Jitter improvement in mark edge recording for phase-change optical disk with optical phase encoding,” Appl. Phys. Lett. 64, 1613–1614 (1994).
[CrossRef]

Peng, C.

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
[CrossRef]

Rubin, K.

M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
[CrossRef]

Rubin, K. A.

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

Sadeghi, K.

Satoh, I.

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

Takao, M.

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

Takenaga, M.

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

van Es-Spiekman, W.

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

Xun, X.

Yamada, N.

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

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

Appl. Opt. (1)

Appl. Phys. Lett. (4)

T. Ide, M. Okada, “Jitter improvement in mark edge recording for phase-change optical disk with optical phase encoding,” Appl. Phys. Lett. 64, 1613–1614 (1994).
[CrossRef]

C. Peng, M. Mansuripur, W. M. Kim, S. G. Kim, “Edge detection in phase-change optical data storage,” Appl. Phys. Lett. 71, 2088–2090 (1997).
[CrossRef]

M. Chen, K. Rubin, R. Barton, “Compound material for reversible, phase-change optical data storage,” Appl. Phys. Lett. 49, 502–504 (1986).
[CrossRef]

M. Chen, K. A. Rubin, V. Marrello, U. G. Gerber, V. B. Jipson, “Reversibility and stability of tellurium alloys for optical data storage applications,” Appl. Phys. Lett. 46, 734–736 (1985).
[CrossRef]

IEEE Trans. Magnet. (1)

T. Ohta, K. Nagata, I. Satoh, R. Imanaka, “Overwritable phase-change optical disk recording,” IEEE Trans. Magnet. 34, 426–431 (1998).
[CrossRef]

J. Appl. Phys. (2)

J. H. Coombs, A. P. J. M. Jongenelis, W. van Es-Spiekman, B. A. J. Jacobs, “Laser-induced crystallization phenomena in Ge-Te-based alloys. I. Characterization of nucleation and growth,” J. Appl. Phys. 78, 4906–4913 (1995).
[CrossRef]

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

Optoelectron. Devices Technol. (1)

T. Ohta, N. Akahira, S. Ohara, I. Satoh, “High-density phase-change optical recording,” Optoelectron. Devices Technol. 10, 361–380 (1995).

Rev. Sci. Instrum. (1)

K. Nishiuchi, N. Yamada, N. Akahira, M. Takenaga, R. Akutagawa, “Laser diode beam exposure instrument for rapid quenching of thin-film material,” Rev. Sci. Instrum. 63, 3425–3430 (1992).
[CrossRef]

Other (2)

T. Ohta, “Study of phase-change optical disk memory,” Ph.D. dissertation (Osaka Prefecture University, Osaka, Japan, 1995).

TEMPROFILE is a product of MM Research Inc., Tucson, Arizona. The theoretical basis of the program is described in M. Mansuripur, G. A. N. Connell, J. W. Goodman, “Laser-induced local heating of multilayers,” Appl. Opt. 21, 1106–1114 (1982) and in M. Mansuripur, G. A. N. Connell, “Laser-induced local heating of moving multilayer media,” Appl. Opt. 22, 666–670 (1983).

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Figures (11)

Fig. 1
Fig. 1

Typical quadrilayer PC optical stack used for the study of crystallization and amorphization processes. The optical and the thermal constants of the various layers are listed in Table 1. The two laser beams are focused on the GST layer through the sample’s substrate, and the microscope objective lens, which focuses the beams, is corrected for the 1.2-mm thickness of this substrate.

Fig. 2
Fig. 2

Photodetector signals (in millivolts) versus time, measured with a 2-µs pulse from laser 1 reflecting off a polished silicon surface. The silicon sample has a nominal reflectivity of 33%. Different plots correspond to different values of the laser power P 1 incident on the sample’s surface. There is ∼6.2 mV of added background signal inherent in these measurements, owing to the offset voltage of the detector amplifier.

Fig. 3
Fig. 3

Reflectivity variations during crystallization of the as-deposited GST film in the quadrilayer stack of Fig. 1. Different curves correspond to different values of the laser pulse power P 1, as indicated on the right-hand side of each curve. The pulse duration was 2 µs, and the monitoring cw laser power P 2 was 0.2 mW. For ease of presentation the curves have been vertically displaced by arbitrary amounts from an original position where R(0) = R a ∼ 3%.

Fig. 4
Fig. 4

Reflectivity variations during melting and subsequent amorphization of the GST film in the quadrilayer stack of Fig. 1. Different curves correspond to different values of the laser pulse power P 1, as indicated on the right-hand side of each curve. The pulse duration was 3 µs, and the monitoring cw laser power P 2 was 0.3 mW. For ease of presentation the curves have been vertically displaced by arbitrary amounts from an original position where R(0) = R c ∼ 20%.

Fig. 5
Fig. 5

Onset time of melting, t onset, in the crystalline GST film versus the laser pulse power P 1. Squares are experimental data points, and the dashed curve is obtained by computer simulations in which the values of the thermal conductivity K of the various layers were adjusted to achieve a good match to the measured data. These values of K are listed in Table 1.

Fig. 6
Fig. 6

Reversible changes occur in the reflectivity of the quadrilayer stack of Fig. 1 under laser heating with a short, relatively low-power pulse prior to the onset of phase transformation. In (a) the GST film is crystallized, whereas in (b) it is in the as-deposited amorphous state. For ease of presentation the curves have been vertically displaced by arbitrary amounts from their original positions. The corresponding pulse power and pulse duration is shown on the right-hand side of each curve.

Fig. 7
Fig. 7

Variations of reflectivity with time during crystallization of the as-deposited GST film under a focused laser beam with different pulse widths, ranging from 0.5 to 4.5 µs, at P 1 = 5.0 mW. The monitoring cw laser power P 2 = 0.2 mW.

Fig. 8
Fig. 8

Net gain in reflectivity ΔR during the cooling period as function of the pulse width obtained in experiments of the type depicted in Fig. 7. The as-deposited amorphous film is started on its crystallization path by a laser pulse of varying duration at a power level of P 1 = 3.0 mW (circles) or P 1 = 5.0 mW (squares).

Fig. 9
Fig. 9

Variations of reflectivity with time during melting and subsequent amorphization of a precrystallized GST film under a focused laser beam with different pulse widths, ranging from 0.5 to 4.0 µs, at P 1 = 9.0 mW. The monitoring cw laser power P 2 = 0.2 mW.

Fig. 10
Fig. 10

Net change in reflectivity as function of the laser pulse width, observed in experiments of the type depicted in Fig. 9. The horizontal axis corresponds to pulse duration, and different symbols are used to represent different pulse magnitudes P 1. (a) Net reflectivity gain ΔR during the cooling period. The vertical axis shows the change in R between the end of the pulse and t = 10 µs. (b) Loss of reflectivity [R(0) - R(∞)] between the beginning of the pulse, when the sample is fully crystallized, and t = 10 µs, when the writing is essentially complete.

Fig. 11
Fig. 11

(a) Computed profiles of temperature versus time in the GST film at the center of the focused spot at P 1 = 8.0 mW for various pulse durations. The simulated quadrilayer stack is depicted in Fig. 1, and its relevant optical and thermal parameters appear in Table 1. (b) The rate of decline of temperature with time in the GST film at the center of the spot immediately after turning off the write pulse. These cooling rates obtained from the temperature profiles in (a) indicate that, by creating a more homogeneous temperature distribution within the stack, a longer pulse causes a slowdown of the cooling process at the end of the pulse.

Tables (1)

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Table 1 Optical and Thermal Constants of the Various Materials Used in the Calculations

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