In situ visualization of silicon wafer casting on silicon carbide as low nucleation undercooling substrate
Journal
Journal of Crystal Growth
Journal Volume
566-567
Date Issued
2021
Author(s)
Abstract
The kerf-free silicon casting utilizing direct contact on a foreign substrate possess is an ultimate wafer technology for solar cells. The use of substrate as a casting surface provides the system better control over the casted wafer's morphological and crystallographic characteristics, and it also grants better control over the temperature distribution to achieve higher throughput. An in situ and infrared temperature measurement study using silicon carbide substrate for the casting of silicon wafers was carried out. Silicon carbide presented a low nucleation undercooling condition for silicon that exhibits circular nucleation at high cooling rates which was very different than those previously observed on silicon nitride and quartz substrates. Recalescence rate estimations showed that the increasing rate of heat of solidification released at the interface could have influenced the grain shape thus effectively localizing each nucleation and preventing large dendritic strip growth. From electron backscatter diffraction (EBSD) analysis, the circular grain growth resulted to an increase in grain randomness when compared to that of dendritic strip growth which showed preference towards common dendrite orientations. The casted wafer exhibited a majority of Σ3 grain boundaries (GB) and with increasing high-Σ GBs at higher cooling rates. The increased randomness and the high-Σ GBs coinciding with the increase in GB density due to the smaller grain sizes at higher cooling rates show potential in the thermoelectric applications that need more phonon scatterings. ? 2021 Elsevier B.V.
Subjects
Crystal growth; Grain boundaries; Grain growth; Random processes; Silicon nitride; Substrates; Temperature measurement; Undercooling; A1.; B2.; B3.; Growth models; High cooling rates; Infrared measurements; Undercoolings; Nucleation
SDGs
Type
journal article