Lay summary
The development of new technologies for the synthesis of innovative one dimensional (1D) materials is a key issue for fabricating advanced nanodevices with unique surface-related effects and quantum phenomena. The nitride nanomaterials, particularly group III nitrides, have attracted great interest due to their blue light and UV emission properties, piezoelectricity, high stability etc. In contrast to oxides, the synthesis of stoichiometric nitrides is a considerably more complicated task due to the lower reactivity of nitrogen. Therefore, the development of new nitridation technologies operating at low synthesis temperatures is a key challenge for modern materials science. The purpose of this project is to develop a hydrazine-based simple and efficient new technology for fabricating new 1D nanomaterials (nitrides, oxynitrides, oxides of Ge and Ge-In, Ge-Sn, Ge-Zn, Ge-Ga systems) and to furthermore investigate the properties of the emerging novel nanomaterials in order to evaluate their application potential in different nanodevices. Our new technological approach is based on the application of hydrazine for producing nitride and oxide nanomaterials. The advantage of hydrazine over ammonia as the conventionally used agent is its low pyrolysis temperature. Semiconductor surfaces then serve as catalysts for the low temperature decomposition of hydrazine via a chain reaction. Due to the low pyrolysis temperature and the formation of active radicals, a decrease of nitridation temperatures with hydrazine as a nitrogen source is expected. Oxynitride 1D nanomaterials will be synthesized following a similar route based on water-hydrazine mixtures. Preliminary syntheses of germanium nitride nanowires by annealing a Ge source in hydrazine vapor containing 3 mol% of water molecules demonstrate the efficiency of our strategy as a simple, low-cost technology aiming for the mass production of functional nitride nanomaterials. Special emphasis will furthermore be placed on the application of the newly synthesized 1D nanomaterials in sensors for environmental control and on the fabrication of nano-sized photocatalysts for solar hydrogen production by water splitting. Germanium nitride was the first non-oxide photocatalyst which was used for water splitting. We suggest that the application of this material in the form of flat nanobelts can increase its catalytic efficiency, because a considerable fraction of the atoms are located at the surface of the nanobelts. The insights obtained from the project will lead to a deeper understanding of 1D nanomaterial growth mechanisms and they will facilitate the transition to the zero dimensional (0D) quantum-dot devices.