Anomalous nucleation of crystals within amorphous germanium nanowires during thermal annealing

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Abstract

In this work, germanium nanowires rendered fully amorphous via xenon ion irradiation have been annealed within a transmission electron microscope to induce crystallization. During annealing crystallites appeared in some nanowires whilst others remained fully amorphous. Remarkably, even when nucleation occurred, large sections of the nanowires remained amorphous even though the few crystallites embedded in the amorphous phase were formed at a minimum of 200°C above the temperature for epitaxial growth and 100°C above the temperature for random nucleation and growth in bulk germanium. Furthermore, the presence of crystallites was observed to depend on the diameter of the nanowire. Indeed, the formation of crystallites occurred at a higher annealing temperature in thin nanowires compared with thicker ones. It is proposed that oxygen atoms hinder both the formation and the growth of crystallites. Furthermore, as crystallites must reach a minimum size to survive and grow within the amorphous nanowires, the instability of crystallites may also play a limited role for the thinnest nanowires with diameters below 15 nm.
Original languageEnglish
Article number285707
JournalNanotechnology
Volume32
Issue number28
Early online date30 Nov 2020
DOIs
Publication statusE-pub ahead of print - 30 Nov 2020

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