Formation of semiconductor epitaxial films by pulse heating crystallization or regrowth

Александров, Л. Н.

doi:10.1002/pssa.2210760121

Cited by 15 publications

(1 citation statement)

References 27 publications

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“…Because of the coexistence of melt and crystallites in zone C, the crystals grow to larger size. Given the fast change in crystallinity (see below), we must consider the mechanism of explosive crystallization (28) that is initiated in zone C and propagates out to create the larger area of fine-grained polycrystalline silicon, allowing for enhanced heat transport out of the hot center (23,24). In this way, a flattening of the heat profile can result in all modified areas falling below the threshold for further crystallization within a few microseconds, as observed.…”

Section: Crystallization Dynamics and Phase Transitionsmentioning

confidence: 99%

4D visualization of embryonic, structural crystallization by single-pulse microscopy

Kwon

Barwick

Park

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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In many physical and biological systems the transition from an amorphous to ordered native structure involves complex energy landscapes, and understanding such transformations requires not only their thermodynamics but also the structural dynamics during the process. Here, we extend our 4D visualization method with electron imaging to include the study of irreversible processes with a single pulse in the same ultrafast electron microscope (UEM) as used before in the single-electron mode for the study of reversible processes. With this augmentation, we report on the transformation of amorphous to crystalline structure with silicon as an example. A single heating pulse was used to initiate crystallization from the amorphous phase while a single packet of electrons imaged selectively in space the transformation as the structure continuously changes with time. From the evolution of crystallinity in real time and the changes in morphology, for nanosecond and femtosecond pulse heating, we describe two types of processes, one that occurs at early time and involves a nondiffusive motion and another that takes place on a longer time scale. Similar mechanisms of two distinct time scales may perhaps be important in biomolecular folding.diffraction ͉ imaging ͉ structural dynamics ͉ ultrafast electron microscopy T he transformation of amorphous structures, such as liquids or random-coiled proteins, into ordered structures involves complex dynamical processes that ultimately lead to the final native state. The mechanism is determined by the scales of time, length, and energy as they define the nature of the elementary steps involved. For example, an amorphous bulk liquid crystallizes depending on the degree of initial (nanoscale) nucleation, the time scale of heat diffusion, and the latent energy acquired. Similarly, for a protein, the funneling toward the native structure requires the balance of the entropic and enthalpic free energy contributions, as well as the ''diffusion'' through many energy barriers, possibly with nucleation on the path to the final state.To observe such processes on the time-length scale of the phenomena, our method of choice has been 4D space-time visualization (ref. 1 and references therein, and ref. 2) developed in ultrafast electron microscopy (UEM) and diffraction for imaging with a wide scope (3) of applications (1-10). For microscopy, the concept of femtosecond single (or few) electron packets was introduced to allow for the study of structural dynamics in the temporal, space-charge-free regime and to obtain the atomic-scale spatial resolution. In this mode of UEM operation, a train of electron packets coherently ''builds up'' and coheres into the final image. However, for nonequilibrium irreversible processes, such as crystallization, the transformation must be visualized through single-pulse imaging.In this contribution, we augment the UEM apparatus to include this single-pulse capability, thus covering domains of femtoseconds (fs) to seconds. Using this mode of imaging, here reported is the ...

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Section: Crystallization Dynamics and Phase Transitionsmentioning

confidence: 99%

4D visualization of embryonic, structural crystallization by single-pulse microscopy

Kwon

Barwick

Park

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Dynamics of Self-Sustaining Crystallization of Amorphous Silicon Layers

Balandin

Двуреченский

Александров

1984

Phys. Stat. Sol. (a)

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Explosive" or self-sustaining crystallization (SSC) of amorphous silicon films is studied by numerical calculations based on the diffusion equation for heat transport, cast in a finite-difference form. Crystallization of amorphous Si goes on through the metastable undercooled liquid. A Iiquid zone is included between the crystalline and amorphous regions. Crystallization is sustained by the releasing heat due to the difference between the enthalpies of crystalline and amorphous Si.

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Simulation of the Influence of Mechanical Stresses on the Kinetics of Crystallization of Ion-Implanted Silicon Layers under Pulse Heating

Александров

1985

phys. stat. sol. (a)

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The method of numerical simulation on two‐layer structures such as a‐SiSi and a‐SiSiO2 is used to study the influence of mechanical stresses on the start temperature of self‐sustaining crystallization of an amorphous film, on the waiting time for the start of crystallization (or melting) t0, and on the expected time of film crystallization tn which is compared to the duration of a heating pulse. In case of simulation of the transformation kinetics the energy of strain field of a lattice during the doping is estimated for the substitutional position of impurity atoms by the difference of their size from that of silicon atoms. Isotropy of the stress field, the local action of an impurity, the possibility of incorporation into a lattice and of excess over equilibrium solubility are included. Numerical calculations are made for the degree of deformation of 0.1 and variations of a free energy by 56 meV and of an activation energy of transformation by 1 eV typical of amorphous silicon obtained by ion implantation. It is shown that (t0 and tn decrease by 103 to 104 times for A → C and by 10 to 103 for A → L transformations, the melting being most likely as usual. The proposed way of taking into account the influence of mechanical stresses can be used in simulation of the crystallization process by the method of finite differences.

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Formation of semiconductor epitaxial films by pulse heating crystallization or regrowth

Cited by 15 publications

References 27 publications

4D visualization of embryonic, structural crystallization by single-pulse microscopy

4D visualization of embryonic, structural crystallization by single-pulse microscopy

Dynamics of Self-Sustaining Crystallization of Amorphous Silicon Layers

Simulation of the Influence of Mechanical Stresses on the Kinetics of Crystallization of Ion-Implanted Silicon Layers under Pulse Heating

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