|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5435678||1398118||2018||7 صفحه PDF||ندارد||دانلود کنید|
The unsteady propagation mechanism for the crystallization of amorphous germanium (a-Ge) was studied with in situ movie-mode dynamic transmission electron microscopy (MM-DTEM). Short laser pulses were used to heat sputter-deposited a-Ge films and the resulting crystallization process was imaged with up to 16 sequential 50 ns long electron pulses separated by a controlled delay that was varied between 0.5 and 5Â Î¼s The unsteady crystallization in the radial, net-growth direction was observed to occur at a decreasing rate of â¼1.5â0.2Â m/s through a mechanism involving the formation of discrete â¼1.1Â Î¼m wide bands that grew with velocities of 9â12Â m/s perpendicular to the radial direction and along the perimeter of the crystallized area. The crystallization rate and resulting microstructure were consistent with a liquid-mediated growth mechanism, which suggests that locally the band front reaches the amorphous melting temperature of Ge. A mechanism based on the notion of a critical temperature is proposed to explain the unsteady, banded behavior.
Graphical abstractDownload high-res image (537KB)Download full-size image
Journal: Acta Materialia - Volume 143, 15 January 2018, Pages 13-19