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Crystallization processes of amorphous germanium–tin (GeSn) under low-energy electron-beam irradiation were examined using transmission electron microscopy (TEM). Freestanding amorphous GeSn thin films were irradiated with a 100 keV electron beam at room temperature. The amorphous GeSn was athermally crystallized by electron-beam irradiation, when the electron flux exceeded the critical value. Heterogeneous structures consisting of nano- and micro-crystallites were formed after crystallization of amorphous GeSn with ∼24 at. % Sn in the as-sputtered amorphous state. In situ TEM observations of structural changes under electron-beam irradiation revealed that random nucleation and growth of nanocrystallites occur at the early stage of crystallization, followed by rapid formation of micro-grains surrounding the nanocrystals. It has been suggested that the growth of micro-grains progresses via supercooled liquid Sn at the amorphous/crystalline interface. The resultant GeSn grains with a size of a few micrometers contained ∼15 at. % Sn, much larger than the solubility limit of Sn in Ge (∼1 at. % Sn). [ABSTRACT FROM AUTHOR]

Solid-phase epitaxy (SPE) and other three-dimensional epitaxial crystallization processes pose challenging structural and chemical characterization problems. The concentration of defects, the spatial distribution of elastic strain, and the chemical state of ions each vary with nanoscale characteristic length scales and depend sensitively on the gas environment and elastic boundary conditions during growth. The lateral or three-dimensional propagation of crystalline interfaces in SPE has nanoscale or submicrometer characteristic distances during typical crystallization times. An in situ synchrotron hard x-ray instrument allows these features to be studied during deposition and crystallization using diffraction, resonant scattering, nanobeam and coherent diffraction imaging, and reflectivity. The instrument incorporates a compact deposition system allowing the use of short-working-distance x-ray focusing optics. Layers are deposited using radio-frequency magnetron sputtering and evaporation sources. The deposition system provides control of the gas atmosphere and sample temperature. The sample is positioned using a stable mechanical design to minimize vibration and drift and employs precise translation stages to enable nanobeam experiments. Results of in situ x-ray characterization of the amorphous thin film deposition process for a SrTiO3/BaTiO3 multilayer illustrate implementation of this instrument. [ABSTRACT FROM AUTHOR]

We present the results of molecular dynamics simulations of the crystal nucleation rate in a supercooled Lennard-Jones liquid. The nucleation rate as a function of the pressure has been calculated by the method of determining the expectation time for liquid crystallization at temperatures higher than that of the triple point (T*=0.865), close to the temperature of the terminal critical point of the metastable extension of the melting curve (T*=0.55) and below this temperature (T*=0.4). In computer experiments the nucleation rate varied from 1032 to 1035 s-1 m-3. The dimensions of critical nuclei and the pressure inside them, the surface free energy at a critical crystal nucleus-liquid interface, the height of the nucleation barrier, and the Zeldovich factor have been determined from the results of molecular dynamics simulations and their comparison with classical homogeneous nucleation theory. It is shown that the surface free energy at a curved crystal-liquid interface, as distinct from a flat interface, has also been determined at temperatures lower than the temperature of the terminal critical point of the melting curve and is a monotonically increasing function of the temperature. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a theory of behavior of foreign solid inclusions in a liquid being crystallized. Methodology of the study; Results and discussion on the study; Conclusions.

Presents a study which examined thermal and diffusion-induced stresses in crystalline solids. Description of the preliminary relation of thermodynamics; Components of the total strain; Details of numerical calculations for the directional crystallization method.

We have measured the density of Pd[sub 40]Ni[sub 40-x]Cu[sub x]P[sub 20] (x=0–40) alloys in the amorphous and crystalline states. For x>30, the alloys are denser in the amorphous than in the crystalline states, which is contrary to the behavior of all known metallic glasses. For Pd[sub 40]Ni[sub 40-x]Cu[sub x]P[sub 20] and all other bulk metallic glasses where density data are available in both the amorphous and crystalline states, we find a correlation between the stability of the supercooled liquids and the difference between the molar volumes of the glassy and crystalline phases. The supercooled liquid region is largest for those alloys that show no change in molar volume upon crystallization. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents an ion-beam-induced epitaxial crystallization (IBIEC)/amorphization model at the amorphous silicon interface. Use of IBIEC for recrystallizing damaged layers; Relationship between recrystallization and amorphization; Dependence of crystallization rate on interface orientation.