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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 23 — Nov. 7, 2011
  • pp: 22684–22691
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Characterization of Femtosecond laser-irradiation crystallization and structure of multiple periodic Si/Sb80Te20 nanocomposite films by coherent phonon spectroscopy

Weiling Zhu, Changzhou Wang, Mingcheng Sun, Simian Li, Jiwei Zhai, and Tianshu Lai  »View Author Affiliations


Optics Express, Vol. 19, Issue 23, pp. 22684-22691 (2011)
http://dx.doi.org/10.1364/OE.19.022684


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Abstract

Multiple parameters of nanocomposite Si/Sb80Te20 multilayer films are possibly optimized simultaneously to satisfy the development of ideal phase-change memory devices by adjusting chemical composition and physical structure of multilayer films. The crystallization and structure of the films are studied by coherent phonon spectroscopy. Laser irradiation power dependence of coherent optical phonon spectroscopy reveals laser-induced crystallization of the amorphous multilayer film, while coherent acoustic phonon spectroscopy reveals the presence of folded acoustic phonons which suggests a good periodic structure of the multilayer films. Laser irradiation-induced crystallization shows applicable potentials of the multilayer films in optical phase change storage.

© 2011 OSA

1. Introduction

Sb2Te3 films have potential applications in high-speed phase change (PC) random access memory devices due to its fast growth-dominated PC mechanism [1

1. L. van Pieterson, M. H. R. Lankhorst, M. van Schijndel, A. E. T. Kuiper, and J. H. J. Roosen, “Phase-change recording materials with a growth-dominated crystallization mechanism: A material review,” J. Appl. Phys. 97(8), 083520 (2005). [CrossRef]

]. However, it has the disadvantages of low crystallization temperature (Tc = 80 °C) [2

2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

] which leads to poor thermal stability of the memorized information, and a high melting temperature (TM = 617) [2

2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

] which results in a large energy consumption during the reset process of data storage. Youm et al found that increasing Sb content in Sb-Te alloy could raise Tc from 80 to 140 °C and reduce the TM from 615 to 543 °C [2

2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

]. Lee et al found that the addition of Ag and In into Sb70T30 could lead to further the increase of Tc up to 168 °C and the reduction of TM down to 526 °C [3

3. M. L. Lee, L. P. Shi, Y. T. Tian, C. L. Gan, and X. S. Miao, “Crystallization behavior of Sb70Te30 and Ag3In5Sb60Te32 chalcogenide materials for optical media applications,” Phys. Status Solidi., A Appl. Mater. Sci. 205(2), 340–344 (2008). [CrossRef]

]. Recently, Simpson et al [4

4. R. E. Simpson, D. W. Hewak, P. Fons, J. Tominaga, S. Guerin, and B. E. Hayden, “Reduction in crystallization time of Sb:Te films through addition og Bi,” Appl. Phys. Lett. 92(14), 141921 (2008). [CrossRef]

] found that the addition of Bi into Sb8Te2 could decrease the crystallization time by an order of magnitude at the concentration of 8 at. % Bi, greatly increasing write rate of data recording in PC memory devices, but the Tc again reduced down to 115 °C from 165 °C. Therefore, it seems difficult to optimize all parameters (Tc, TM, crystallization time and resistivity in crystalline state etc.) of SbTe alloy only by the doping or adjustment of Sb content [1

1. L. van Pieterson, M. H. R. Lankhorst, M. van Schijndel, A. E. T. Kuiper, and J. H. J. Roosen, “Phase-change recording materials with a growth-dominated crystallization mechanism: A material review,” J. Appl. Phys. 97(8), 083520 (2005). [CrossRef]

]. Wang et al just reported on a multiple periodic nanocomposite Si/Sb80Te20 multilayer film [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

], and found that the Tc and resistivity of the multilayer film might be adjusted by the thickness of Si and/or Sb80Te20 layers. They found Tc increased with increasing (reducing) Si (Sb80Te20) layer thickness, and could range largely from 120 to 220 °C. Meanwhile, they also found that the resistivity of the multilayer film in the crystallized state was increased at least by two orders of magnitude, leading to a driven current reduced at least by one order of magnitude during the reset process of data recording. Therefore, combining adjustments of SbTe alloy composition with of Si/SbTe multilayer structure, it is obvious possibly to optimize all parameters of the multilayer films for the development of ideal PC memory devices. Furthermore, Wang et al [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

] also realized current-driven PC recording/erasing with 50 ns electrical pulses. However, it is unknown yet whether the nanocomposite films are suitable for optical PC storage because no data has been reported so far on laser-induced crystallization of the films.

In this article, femtosecond laser-irradiation-induced crystallization of the nanocomposite films is investigated in situ using coherent phonon spectroscopy. It is well known that the coherent phonon spectroscopy is a powerful spectroscopic tool and very sensitive to microstructure change induced by phase change [6

6. M. Först, T. Dekorsy, C. Trappe, M. Laurenzis, H. Kurz, and B. Béchevet, “Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy,” Appl. Phys. Lett. 77(13), 1964 (2000). [CrossRef]

] or even different doping type [7

7. K. Kato, K. Oguri, A. Ishizawa, K. Tateno, T. Tawara, H. Gotoh, M. Kitajima, H. Nakano, and T. Sogawa, “Doping-type dependence of phonon dephasing dynamics in Si,” Appl. Phys. Lett. 98(14), 141904 (2011). [CrossRef]

]. It has been extensively used to characterize microstructure change by detecting characteristic phonon modes of various microstructures [6

6. M. Först, T. Dekorsy, C. Trappe, M. Laurenzis, H. Kurz, and B. Béchevet, “Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy,” Appl. Phys. Lett. 77(13), 1964 (2000). [CrossRef]

, 8

8. Y. W. Li, V. A. Stoica, L. Endicott, G. Y. Wang, C. Uher, and R. Clarke, “Coherent optical phonon spectroscopy studies of femtosecond-laser modified Sb2Te3 films,” Appl. Phys. Lett. 97(17), 171908 (2010). [CrossRef]

]. Thus, laser-induced crystallization and coherent phonon dynamics of the Si/Sb80Te20 multilayer films are studied by coherent phonon spectroscopy. Coherent optical phonon spectra reveal the laser-induced crystallization of Sb80Te20 layer, while coherent acoustic phonon spectra, especially folded acoustic phonon spectra observed, expose good periodic structure of the multilayer films. It is shown that the multilayer films also have good potentials in the application of optical PC storage because it has a higher crystallization (170 °C) [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

] and lower melting (543 °C) [2

2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

] temperatures than the crystallization (140 °C) [6

6. M. Först, T. Dekorsy, C. Trappe, M. Laurenzis, H. Kurz, and B. Béchevet, “Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy,” Appl. Phys. Lett. 77(13), 1964 (2000). [CrossRef]

] and melting (632 °C) [2

2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

] temperatures of the phase change material of Ge2Sb2Te5 which is used commercially, respectively.

2. Sample and experiment

Two samples studied consist of ten periods of Si/Sb80Te20 films, where the Si and Sb80Te20 layer films all are 5 nm thick, and are grown on glass substrates by radio frequency magnetron sputtering using Si and Sb80Te20 targets. All depositions are performed at room temperature to ensure as-deposited films in the amorphous phase. The details on the conditions and procedures of the multilayer film preparation were described elsewhere [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

]. One of the samples was heated in the protective Ar-atmosphere at a heating rate of 10 °C/min. Meanwhile, temperature dependence of the sheet resistance of the sample was measured, and showed that the phase change occurred at 170 °C [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

]. Therefore, the thermal stability of [Si/Sb80Te20]10 films is enhanced greatly. In the following, the sample heated is referred to as “crystallized”, while the as-deposited sample as “amorphous”.

Time-resolved pump-probe photo-reflectivity spectroscopy is used to study the coherent phonon dynamics of the amorphous and crystallized multilayer films. A train of 60 femtosecond pulse laser from a self-mode-locked Ti: sapphire laser oscillator with the central wavelength of 840 nm and a pulse repetition rate of 94 MHz is directed into a standard pump-probe setup, and split into parallel two beams of lasers, a strong pump and a weak probe beams with a pump-to-probe intensity ratio of >15. The emerged pump and probe transmit through a convex lens of 50 mm focal length and are focused nearly normally to a same area on the surface of the sample located at the back focal plane of the lens. The probe reflected from the sample surface is detected by a Si photodiode whose output electrical signal is measured by a lock-in amplifier which is referenced at the modulation frequency of an optical chopper that modulated the pump beam at 1.13 kHz. All optical experimental measurements are performed at room temperature and under a low pump power of 15 mW to avoid any pump-induced PC.

Raman scattering measurement is performed with a ReniShaw inVia Reflex Raman spectrometer at 514.5 nm laser excitation.

3. Results and discussion

3.1 In situ characterization of laser irradiating crystallization

To understand the origin of peak at 3.90 THz, the laser irradiation crystallization of a 5 nm thick as-deposited Sb80Te20 film on a glass substrate is studied as a function of LIP by CPS. The FFT spectra of COP are obtained as described afore and plotted Fig. 3(a)
Fig. 3 (a) FFT spectra of COP of a 5 nm thick amorphous Sb80Te20 film for different LIP. (b) Raman spectra of 5 nm-thick single layer and multilayer amorphous Sb80Te20 films.
for different LIP. The spectra look quite similar to those in Fig. 2(b), and contain two peaks at 3.90 and 4.52 THz. The latter peak enhances with increasing LIP, showing its laser-irradiation resultant. The coexistence of 3.90 THz modes in single layer Sb80Te20 and multilayer films shows that it originates from amorphous Sb80Te20 and does not relate to Si layer in the multilayer film. Therefore, we conjecture the broad peak at 3.90 THz originates from a characteristic phonon mode of amorphous Sb80Te20 films. A Raman scattering measurement on amorphous 5 nm-thick single layer Sb80Te20 and multilayer films is performed. Raman spectra are plotted in Fig.3(b). Obviously, a broad peak appears at 4.14 THz for both amorphous films. It should correspond to the broad peak at 3.90 THz in COP spectra, while small difference between 3.90 and 4.14 THz may be ascribed to systematic and experimental errors between two different measurement methods. Therefore, Raman peak at 4.14 THz provides strong evidence for the assignment of COP mode at 3.90 THz to the phonon mode of amorphous Sb80Te20 film. The phenomenon of which amorphous phase has itself characteristic phonon mode different from the mode of crystalline phase was also observed in amorphous Ge2Sb2Te5 film [12

12. J. Hernandez-Rueda, A. Savoia, W. Gawelda, J. Solis, B. Mansart, D. Boschetto, and J. Siegel, “Coherent optical phonons in different phases of Ge2Sb2Te5 upon strong laser excitation,” Appl. Phys. Lett. 98(25), 251906 (2011). [CrossRef]

]. Meanwhile, the observation of COP mode in the amorphous film also shows higher detection sensitivity of CPS to microstructures than nano-beam electron diffraction which did not show observable diffraction patterns in the amorphous multilayer film [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

]. On the other hand, Fig. 3(a) shows a crystallization threshold power occurs at ~85 mW for single layer film, whereas Fig. 2(b) does a lower one of ~45 mW for the multilayer film. The falling of crystallization threshold power is helpful to reduce writing power of optical storage devices.

To directly understand the laser irradiation-induced PC, a contrast experiment is carried out on the crystallized multilayer film. The transient photoreflectance change is taken. The oscillatory component of COPs is extracted by the method mentioned afore and plotted in Fig. 4(a)
Fig. 4 (a) Transient oscillation of coherent optical phonons in the multilayer films crystallized by annealing and 55 mW laser irradiation, respectively. (b) FFT spectra corresponding to (a). The baselines are shifted upward for clarity in (a) and (b).
by top transient. For comparison conveniently, the transient oscillation of the amorphous film irradiated by 55 mW laser (top curve in Fig. 2(a)) is also re-plotted in Fig. 4(a) (bottom curve). Their FFT spectra are plotted in Fig. 4(b) and look almost the same except the peak amplitude scale at 4.52 THz. Both FFT spectra present a sharp peak at 4.52 THz, showing two sample films containing the same phases, while the annealed film was confirmed in the crystallized state by the sheet resistance measurement and nano-beam electron diffraction [5

5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

]. Therefore, it is directly proven that femtosecond laser irradiation can lead to the crystallization of the amorphous multilayer film.

3.2 Characterization of multilayer film structure

If one views the transient traces more carefully in Fig. 1, one can find there are some low frequency oscillations besides a high frequency oscillation from COPs. Then, what do the low frequency oscillations reflect? To understand the origin of the low frequency oscillations, large time scale transient photoreflectance changes are taken, and plotted in Fig. 5
Fig. 5 Large time-scale transient photoreflectance changes taken on the amorphous and crystallized films. Laser irradiation crystallized film means the amorphous film irradiated by a 55 mW laser.
for the amorphous film and crystallized samples films by annealing and laser irradiation, respectively.

Three transient traces look very similar except the dynamic behavior in first ten picoseconds. More importantly, the low frequency oscillation looks not harmonic. Therefore, it may be synthesized by multiple low frequency harmonic oscillations. Thus, it is very necessary to obtain their spectra.

ωm=v|2πmd1+d2+q|,(m=0,±1,±2,,)
(1)

Where the m denotes the folded index. For the given folded index m = 0, −1 and + 1, one can obtained f0 = ω0/2π = 0.034 THz, f-1 = ω-1 /2π = 0.296 THz, and f+1 = ω+1/ 2π = 0.364 THz by Eq. (1). Evidently, these calculated frequency values (0.034, 0.296, 0.364) agree well with the experimental values (0.035, 0.261, 0.335) in Fig. 6(b) with considerations of uncertain errors of multiple parameters used in the calculations. Therefore, we can assign the three frequencies of 0.035, 0.261, and 0.335 THz to 0-, −1-, and + 1-order FAP modes of the periodic multilayer films, respectively. As for the peak at ~0.133 THz, it may be one of satellite lines originating from the standing acoustic phonon waves in finite-size superlattice [15

15. P. X. Zhang, D. J. Lockwood, and J.-M. Baribeau, “Acoustic phonon peak splitting and satellite lines in Raman spectra of semiconductor superlattices,” Appl. Phys. Lett. 62(3), 267–269 (1993). [CrossRef]

]. Actually, one can indeed see fine structures or satellite peaks between m = 0 and m = −1 peaks. The observation of FAPs shows good periodic structure of the multilayer films.

4. Conclusion

The laser-induced crystallization and structure of the multilayer films have been studied by CPS. COP and CAP are observed, and mainly reflect local microstructure and periodicity of the multilayer structure, respectively. Laser irradiation power dependence of COP reveals laser-induced phase change. The similarity between COP spectra of the films phase-changed by laser irradiation and annealing reveals that laser irradiation indeed leads to the crystallization of amorphous film. The observation of FAPs shows good periodicity of the multilayer films. In addition, a new characteristic phonon mode at 3.90 THz of 5 nm thick amorphous Sb80Te20 films is observed and identified by CPS and Raman, respectively.

Acknowledgments

This work is partially supported by National Natural Science Foundation of China under grant Nos. 10874247, 61078027, National Basic Research and High Technology Development Programs of China under grant Nos. 2010CB923200, 2008AA031402, and Natural Science Foundation of Guangdong Province under grant No. 9151027501000077 as well as doctoral specialized fund of MOE of China under grant No. 20090171110005.

References and links

1.

L. van Pieterson, M. H. R. Lankhorst, M. van Schijndel, A. E. T. Kuiper, and J. H. J. Roosen, “Phase-change recording materials with a growth-dominated crystallization mechanism: A material review,” J. Appl. Phys. 97(8), 083520 (2005). [CrossRef]

2.

M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci. 205(7), 1636–1640 (2008). [CrossRef]

3.

M. L. Lee, L. P. Shi, Y. T. Tian, C. L. Gan, and X. S. Miao, “Crystallization behavior of Sb70Te30 and Ag3In5Sb60Te32 chalcogenide materials for optical media applications,” Phys. Status Solidi., A Appl. Mater. Sci. 205(2), 340–344 (2008). [CrossRef]

4.

R. E. Simpson, D. W. Hewak, P. Fons, J. Tominaga, S. Guerin, and B. E. Hayden, “Reduction in crystallization time of Sb:Te films through addition og Bi,” Appl. Phys. Lett. 92(14), 141921 (2008). [CrossRef]

5.

C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process. 103(1), 193–198 (2011). [CrossRef]

6.

M. Först, T. Dekorsy, C. Trappe, M. Laurenzis, H. Kurz, and B. Béchevet, “Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy,” Appl. Phys. Lett. 77(13), 1964 (2000). [CrossRef]

7.

K. Kato, K. Oguri, A. Ishizawa, K. Tateno, T. Tawara, H. Gotoh, M. Kitajima, H. Nakano, and T. Sogawa, “Doping-type dependence of phonon dephasing dynamics in Si,” Appl. Phys. Lett. 98(14), 141904 (2011). [CrossRef]

8.

Y. W. Li, V. A. Stoica, L. Endicott, G. Y. Wang, C. Uher, and R. Clarke, “Coherent optical phonon spectroscopy studies of femtosecond-laser modified Sb2Te3 films,” Appl. Phys. Lett. 97(17), 171908 (2010). [CrossRef]

9.

Y. G. Wang, X. F. Xu, and R. Venkatasubramanian, “Reduction in coherent phonon lifetime in Bi2Te3/Sb2Te3 superlattices,” Appl. Phys. Lett. 93(11), 113114 (2008). [CrossRef]

10.

G. A. Garrett, T. F. Albrecht, J. F. Whitaker, and R. Merlin, “Coherent THz phonons driven by light pulses and the Sb problem: what is the mechanism,” Phys. Rev. Lett. 77(17), 3661–3664 (1996). [CrossRef] [PubMed]

11.

J. B. Renucci, W. Richter, M. Cardona, and E. Schönherr, “Resonance Raman scattering in group Vb semimetals: As, Sb, and Bi,” Phys. Status Solidi, B Basic Res. 60(1), 299–308 (1973). [CrossRef]

12.

J. Hernandez-Rueda, A. Savoia, W. Gawelda, J. Solis, B. Mansart, D. Boschetto, and J. Siegel, “Coherent optical phonons in different phases of Ge2Sb2Te5 upon strong laser excitation,” Appl. Phys. Lett. 98(25), 251906 (2011). [CrossRef]

13.

A. Bartels, T. Dekorsy, H. Kurz, and K. Köhler, “Coherent zone-folded longitudinal acoustic phonons in semiconductor superlattices: excitation and detection,” Phys. Rev. Lett. 82(5), 1044–1047 (1999). [CrossRef]

14.

C. Colvard, R. Merlin, M. V. Klein, and A. C. Gossard, “Observation of folded acoustic phonons in semiconductor superlattice,” Phys. Rev. Lett. 45(4), 298–301 (1980). [CrossRef]

15.

P. X. Zhang, D. J. Lockwood, and J.-M. Baribeau, “Acoustic phonon peak splitting and satellite lines in Raman spectra of semiconductor superlattices,” Appl. Phys. Lett. 62(3), 267–269 (1993). [CrossRef]

16.

N. Shimidzu, T. Nagatsuka, Y. Magara, N. Ishii, N. Kinoshita, and K. Sato, “Dynamic observation study of crystallization process in Sb-based phase-change materials,” Jpn. J. Appl. Phys. 46(16), L385–L387 (2007). [CrossRef]

17.

K. J. Singh, R. Satoh, and Y. Tsuchiya, “Structure changes and compound forming effects in the molten Sb-Te system investigated by molar volume and sound velocity measurements,” J. Phys. Soc. Jpn. 72(10), 2546–2550 (2003). [CrossRef]

18.

L. R. Testardi and J. J. Hauser, “Sound velocity in amorphous Ge and Si,” Sol. Phys. Comm. 21(11), 1039–1041 (1977). [CrossRef]

19.

Y. G. Wang, C. Leibig, X. F. Xu, and R. Venkatasubramanian, “Acoustic phonon scattering in Bi2Te3/Sb2Te3 superlattices,” Appl. Phys. Lett. 97(8), 083103 (2010). [CrossRef]

20.

S. K. Kim, Y. S. Kim, M. A. Kang, J. M. Sohn, and K. No, “Optical properties of a-Si films for 157 nm lithography,” Proc. SPIE 5130, 127–135 (2003). [CrossRef]

21.

Y.-C. Her, H. Chen, and Y.-S. Hsu, “Effects of Ag and In addition on the optical properties and crystallization kinetics of eutectic Sb70Te30 phase-change recording film,” J. Appl. Phys. 93(12), 10097–10103 (2003). [CrossRef]

OCIS Codes
(160.2900) Materials : Optical storage materials
(210.4770) Optical data storage : Optical recording
(300.6500) Spectroscopy : Spectroscopy, time-resolved
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors

ToC Category:
Optical Data Storage

History
Original Manuscript: September 21, 2011
Revised Manuscript: October 17, 2011
Manuscript Accepted: October 17, 2011
Published: October 26, 2011

Citation
Weiling Zhu, Changzhou Wang, Mingcheng Sun, Simian Li, Jiwei Zhai, and Tianshu Lai, "Characterization of Femtosecond laser-irradiation crystallization and structure of multiple periodic Si/Sb80Te20 nanocomposite films by coherent phonon spectroscopy," Opt. Express 19, 22684-22691 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-23-22684


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References

  1. L. van Pieterson, M. H. R. Lankhorst, M. van Schijndel, A. E. T. Kuiper, and J. H. J. Roosen, “Phase-change recording materials with a growth-dominated crystallization mechanism: A material review,” J. Appl. Phys.97(8), 083520 (2005). [CrossRef]
  2. M. S. Youm, Y. T. Kim, Y. H. Kim, and M. Y. Sung, “Effects of excess Sb on crystallization of δ-phase SbTe binary thin films,” Phys. Status Solidi., A Appl. Mater. Sci.205(7), 1636–1640 (2008). [CrossRef]
  3. M. L. Lee, L. P. Shi, Y. T. Tian, C. L. Gan, and X. S. Miao, “Crystallization behavior of Sb70Te30 and Ag3In5Sb60Te32 chalcogenide materials for optical media applications,” Phys. Status Solidi., A Appl. Mater. Sci.205(2), 340–344 (2008). [CrossRef]
  4. R. E. Simpson, D. W. Hewak, P. Fons, J. Tominaga, S. Guerin, and B. E. Hayden, “Reduction in crystallization time of Sb:Te films through addition og Bi,” Appl. Phys. Lett.92(14), 141921 (2008). [CrossRef]
  5. C. Wang, J. Zhai, Z. Song, F. Shang, and X. Yao, “Phase-change behavior in Si/Sb80Te20 nanocomposite multilayer films,” Appl. Phys., A Mater. Sci. Process.103(1), 193–198 (2011). [CrossRef]
  6. M. Först, T. Dekorsy, C. Trappe, M. Laurenzis, H. Kurz, and B. Béchevet, “Phase change in Ge2Sb2Te5 films investigated by coherent phonon spectroscopy,” Appl. Phys. Lett.77(13), 1964 (2000). [CrossRef]
  7. K. Kato, K. Oguri, A. Ishizawa, K. Tateno, T. Tawara, H. Gotoh, M. Kitajima, H. Nakano, and T. Sogawa, “Doping-type dependence of phonon dephasing dynamics in Si,” Appl. Phys. Lett.98(14), 141904 (2011). [CrossRef]
  8. Y. W. Li, V. A. Stoica, L. Endicott, G. Y. Wang, C. Uher, and R. Clarke, “Coherent optical phonon spectroscopy studies of femtosecond-laser modified Sb2Te3 films,” Appl. Phys. Lett.97(17), 171908 (2010). [CrossRef]
  9. Y. G. Wang, X. F. Xu, and R. Venkatasubramanian, “Reduction in coherent phonon lifetime in Bi2Te3/Sb2Te3 superlattices,” Appl. Phys. Lett.93(11), 113114 (2008). [CrossRef]
  10. G. A. Garrett, T. F. Albrecht, J. F. Whitaker, and R. Merlin, “Coherent THz phonons driven by light pulses and the Sb problem: what is the mechanism,” Phys. Rev. Lett.77(17), 3661–3664 (1996). [CrossRef] [PubMed]
  11. J. B. Renucci, W. Richter, M. Cardona, and E. Schönherr, “Resonance Raman scattering in group Vb semimetals: As, Sb, and Bi,” Phys. Status Solidi, B Basic Res.60(1), 299–308 (1973). [CrossRef]
  12. J. Hernandez-Rueda, A. Savoia, W. Gawelda, J. Solis, B. Mansart, D. Boschetto, and J. Siegel, “Coherent optical phonons in different phases of Ge2Sb2Te5 upon strong laser excitation,” Appl. Phys. Lett.98(25), 251906 (2011). [CrossRef]
  13. A. Bartels, T. Dekorsy, H. Kurz, and K. Köhler, “Coherent zone-folded longitudinal acoustic phonons in semiconductor superlattices: excitation and detection,” Phys. Rev. Lett.82(5), 1044–1047 (1999). [CrossRef]
  14. C. Colvard, R. Merlin, M. V. Klein, and A. C. Gossard, “Observation of folded acoustic phonons in semiconductor superlattice,” Phys. Rev. Lett.45(4), 298–301 (1980). [CrossRef]
  15. P. X. Zhang, D. J. Lockwood, and J.-M. Baribeau, “Acoustic phonon peak splitting and satellite lines in Raman spectra of semiconductor superlattices,” Appl. Phys. Lett.62(3), 267–269 (1993). [CrossRef]
  16. N. Shimidzu, T. Nagatsuka, Y. Magara, N. Ishii, N. Kinoshita, and K. Sato, “Dynamic observation study of crystallization process in Sb-based phase-change materials,” Jpn. J. Appl. Phys.46(16), L385–L387 (2007). [CrossRef]
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