Subproject 1



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


Within the framework of this sub-project, we want to gain an insight into the chemistry of the main group elements viz. gallium, silicon, germanium and aluminum in fluid and supercritical ammonia. The aim is to explore the growth, solution and crystallization behavior of ternary and higher nitridosilicates, nitridogallates, nitridogermanates and nitridoaluminates. The reactions will be studied under the influence of different ammonobasic and ammoacidic mineralizers and under ammonothermal conditions in special high-pressure autoclaves (1073 K and 170 MPa) with respects to the temperature, temperature gradients, pressure and reaction time as well as concentration of reactants. Intermediates (e. g. ammoniates, amides, imides) resulting from this process as well as the expected end products of ternary and multinary nitrides (or nitridimides) are to be isolated, identified and characterized structurally regarding their properties. In this case, special attention should be paid to the optical and electronic properties with respect to semiconductor technology. The investigations shall not only help bridge the gaps in knowledge of inorganic chemistry of main group elements but also produce valuable quantative information regarding the conditions required for synthesis and crystal growth of important ternary and higher nitridosilicates, nitridogallates, nitridogermanates and nitridoaluminates like ZnSiN2 or ZnGeN2. Furthermore, the ammonothermal method should be used for the synthesis and crystal growth of interesting oxonitrides like LaTaON2.

The research group and especially this subproject focuses on the reestablishment and further development of the almost forgotten ammonothermal process, which was developed by Professor Jacobs a few decades ago. Consequently, the ammonothermal synthesis shall provide a tool for the explorative investigation, the synthesis itself and crystal growth of nitrides, amides and imides. In the recent developments of the current solid state and material chemistry the ammonothermal process could become as important as the hydrothermal synthesis for oxide compounds.