Ammonothermal synthesis of binary and multinary nitrides, amides and imides of Ga, Al, Si and Ge

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During the last couple of years, main group nitrides got in the focus of numerous investigations . Especially compounds of group III (Al, Ga, In) and group IV (Si, Ge) elements show interesting material properties . Typical syntheses are hereby based on pyrolysis of molecular precursors, solid-state reactions at rather high temperatures or the use of salts or metals acting as fluxing agents. These routes usually enable access only to single crystals inµm scale of these ternary or multinary compounds . Here, ammonothermal reactions could be an attractive alternative. The huge potential of solvothermal syntheses for growing !arge single crystals, for example hydrothermal processing of quartz, is well known for a long time. A similar technique can be used for the synthesis of nitrides employing supercritical ammonia, which can act as solvent as well as nitrogen source. Beyond the Forschergruppe AmmonoFOR1600 ammonothermal processing finds only minor application, although the academic background has been generated in Germany decades ago . The scope of this subproject is to reestablish ammonothermal synthesis, focusing on synthesis and crystal growth of novel multinary nitrides including the elements Al, Ga, Mg, Li, Si or Ge. Hitherto, nitrides, also including alkaline and alkaline earth or rare earth metals as well as intermediates, obtained during synthesis will be structurally characterized. Understanding reaction mechanisms and characterization of intermediates should help to enable a targeted synthesis of novel nitride compounds . Furthermore, it is essential to elucidate the structures of these nitrides, investigate material properties and understand structure-property­ relationships. Within the first funding period it was possible to optimize synthesis conditions and to evaluate appropriate multinary model compounds. lnvestigations showed that nitrides crystallizing in wurtzite type of structure or related superstructures (e.g. LiSbN3 or CaAISiN3)seem to be very promising model candidates.