Rapid Crystallization of Levitated and Undercooled Semiconducting Material Melts

Abstract

Using a CO 2 laser-equipped electromagnetic levitator, we carried out the containerless crystallization of Si and Ge. From the point of interface morphologies, the relation between growth velocities and undercoolings was classified into three regions. In regions I and II, although the morphologies of growing crystals are different: plate-like needle crystals in region I and facetted dendrite at region II, the growth velocities in these two regions are fundamentally scaled by the thermal diffusivities and the temperature increase caused by the release of the latent heat. This result means that the growth velocity can be expressed by the product of the thermal diffusivity and the growth kinetics. An analysis of the dendrite morphologies revealed that the kinetics of crystal growth in regions I and II represent two-dimensional nucleation at the reentrant corner formed at the edge of the two parallel twins. In region III, thermal diffusion-controlled interface attachment kinetics control as described by a modified Wilson-Frenkel model.

Experiments to understand crystallization of levitated high temperature silicate melt droplets under low vacuum conditions

“…Nagashio et al 22 performed real-time XRD experiments to understand the grain refinement dynamics involved during solidification of Si. These growth mechanisms have been observed to vary with levels of undercoolings for Si and Ge melts 23 . A numerical study was carried out by Miura et al 24 on the effect of supercooling and cooling rate on the growth mechanism for forsterite melts.…”

Focused Nanosecond Pulsed Laser‐Induced Homogeneous Nucleation in Undercooled Oxide Melts

“…[14][15][16][17][18] Through this approach, induced nucleation at deep undercooling becomes possible. The induced nucleation of solid phase with containerless processing in a undercooled liquid can be initiated using different mechanisms: heterogeneous nucleation, such as probe needle method, [19,20] and homogeneous nucleation, such as cooling rate control. [14,15,[21][22][23][24][25] Meanwhile, light controlled nucleation was used as promising primary homogeneous-induced nucleation methods for various transparent supersaturation solutions, such as the nonphotochemical laser-induced nucleation method and laser shock wave method.…”