In situ dynamic transmission electron microscopy characterization of liquid-mediated crystallization of amorphous Ge
[3];
- Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA
- Department of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon 97331, USA
- IBM/Macronix PCRAM Joint Project, Macronix Emerging Central Laboratory, Macronix International Co., Hsinchu, Taiwan
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, D-14109 Berlin, Germany
Crystal growth rates during laser-induced, liquid-mediated crystallization of amorphous Ge were measured with movie-mode dynamic transmission electron microscopy (MM-DTEM), a photoemission microscopy technique with nanosecond-scale time resolution. Films of 50-nm thick amorphous Ge were crystallized using a 12-ns laser pulse with a Gaussian spatial profile, which established high local temperature gradients in the specimen. Crystallization proceeded by the formation of a central zone with a high nucleation rate (zone I), followed by liquid-mediated outward growth of columnar grains (zone II), followed by spiraling growth (zone III) until the crystallization halted in cooler parts of the specimen. Zone II growth was imaged for several laser pulse energies with 20-ns electron pulses with 95 ns between frames. A thin liquid layer between the solid amorphous phase and the advancing crystallization front during zone II growth was imaged. The zone II growth rate for each experiment remained nearly constant although the crystallization front passes through a large temperature gradient. Measured growth rates ranged from 5.7 to 13.6 m/s, consistent with transient liquid layer mediated growth rather than solid-state growth. In contrast with a previous report, the growth rate did not increase systematically with laser energy or absorbed energy. The new results, together with previously reported data, suggest that both sets of experiments were conducted under conditions where the growth rate saturates near its maximum value. A phenomenological model based on the concept of upper and lower threshold temperatures for the zone II growth was fitted to the data from these experiments and previous MM-DTEM crystallization experiments.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
- Grant/Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1581487
- Report Number(s):
- LLNL-JRNL--764056; 954020
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 10 Vol. 126; ISSN JAPIAU; ISSN 0021-8979
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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