Interface diagnostics: In-situ prediction of constitutional supercooling and backmelting by growth interface electromotive force

•A growth interface electromotive force (GEMF) method is proposed to detect interface instability during crystal growth.•GEMF method can quantitatively predict constitutional supercooling and backmelting phenomena.•Stable growth, constitutional supercooling, and backmelting regions are clearly distinguished during crystal growth.•As feedback, GEMF method can be used to fabricate unique microstructures as optical gratings, core fibers, and p-n junctions.