Leading Wave Crystallization Induced by Micro-Thermal-Plasma-Jet Irradiation of Amorphous Silicon Films

Abstract

The crystalline grain growth of silicon induced by micro-thermal-plasma-jet irradiation has been directly observed using a high-speed camera. An oval-shaped molten region (MR) was formed after the solid phase crystallization (SPC), and it was clearly observed that laterally large grains grew perpendicular to the liquid–solid interface. Leading wave crystallization (LWC), which showed intermittent grain growth with a liquid–solid interface velocity as high as 4500 mm/s, was discovered in between the MR and SPC region. From numerical calculation, it has been clarified that the explosive lateral growth of LWC is triggered by the formation of a thin liquid layer and the explosive propagation of the layer is driven by released latent heat.

Self-propagating waves of crystallization in metallic glasses

“…We can assume here that the real EC wave propagates faster inside the crystalline grain and stays at the grain boundaries, which decreases the average macroscopic propagation velocity. A similar effect of rapid propagation of short distances followed by delays at the boundaries between structural elements was also observed for propagation of the crystallization wave along a chain of amorphous Ni particles 33 , and periodic "leading wave crystallization" in amorphous Si films 24 .…”

“…Some deposited amorphous metal or semiconductor films exhibit peculiar phenomena named "explosive crystallization", i.e. rapid self-propagation of the amorphous-crystalline transformation in the form of a thermal wave 1,[20][21][22][23][24] . However, this phenomenon has not been observed in metallic glasses produced by melt quenching.…”

“…We should note that EC in the deposited semiconductor films is used for converting amorphous Si, Ge, etc. into polycrystalline materials required for solar cells [21][22][23][24] . The SEC can play a similar role for metallic glasses.…”

Investigation of silicon grain structure and electrical characteristics of TFTs fabricated using different crystallized silicon films by atmospheric pressure micro-thermal-plasma-jet irradiation

“…The LWC mechanism was investigated by performing numerical calculations based on the LWC model. 22) The melting of the SPC region triggers the explosive crystalline growth. The melting point of SPC-Si is lower than that of c-Si because of the lower crystallinity.…”

“…Three crystallization modes of SPC, LWC, and HSLC are induced in that order by increasing the annealing temperature. 22) Therefore, these crystallization modes can be easily controlled by adjusting the annealing conditions such as the supply power of µ-TPJ and the scanning speed of the substrate. In this work, we have investigated the grain structures of Si films formed by different methods of crystalline growth applied to TFT channels.…”