AC Kolloquium - Prof. Dr. Rainer Niewa

Universität Stuttgart - "Main Group Nitrides and Intermediates in Synthesis from Ammonia and Alkali Metal Melts"⠀

Crystal growth of new chemical compounds as well as functional materials often proceeds from solvents and fluxes. This presentation discusses products and chemistry of crystal growth of main group element nitrides from ammonia and molten alkali metal as two prominent approaches.
The ammonothermal synthesis typically uses ammonobasic or ammonoacidic mineralizers in supercritical ammonia at elevated temperatures and pressures, and has been shown to be able to grow a wide range of interesting materials such as AlN crystals and free-standing GaN wafers. The latter have proven to be ideal substrates for manufacturing blue and white LEDs with superior performance. However, the crystal growth mechanism in the ammonothermal synthesis in terms of the involved solute species was poorly understood, although the chemical processes during dissolution of the starting material, [...]