Aluminum-doped ZnO nanoparticles: gas-phase synthesis and dopant location
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Aluminum-doped ZnO (AZO) nanoparticles are studied widely as transparent conducting alternatives for indium tin oxide. However, the properties of AZO vary in different investigations not only with the amount of dopant and the particle size, but also with other parameters such as synthesis method and conditions. Hence, AZO nanoparticles, synthesized in the gas phase, were investigated to study the influence of the synthesis parameters dopant level, reactor temperature and residence time in the reaction zone on the particle characteristics. The local structure of the dopant in semiconductors determines whether the doping is functional, i.e., whether mobile charge carriers are generated. Therefore, information obtained from 27Al solid-state NMR spectroscopy, X-ray diffraction, photoluminescence and UV–Vis spectroscopy was used to understand how the local structure influences particles characteristics and how the local structure itself can be influenced by the synthesis parameters. In addition to AZO particles of different Al content, pure ZnO, Al2O3, ZnAl2O4 and core–shell particles of ZnO and Al2O3 were synthesized for comparison and aid to a deeper understanding of the formation of AZO nanoparticles in the gas phase.
KeywordsZnO AZO 27Al solid-state NMR Chemical vapor synthesis Doping Dopant Local structure
Financial support was granted by the German Research Foundation (DFG) through the Research Training Group GRK1240 (Nanotronics—Photovoltaik und Optoelektronik aus Nanopartikeln) and by the Europian Union and by the Ministry of Innovation, Science and Research of the German State of North Rhine-Westphalia (NanoEnergieTechnikZentrum, NETZ). We would also like to thank Sebastian Kluge for the help on the PL and UV–Vis measurements and Samer Suleiman for EDX–SEM analysis and the Lab for Microanalytics and Thermal Analysis of the University Duisburg-Essen for the AAS measurements.
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