Room temperature vacuum-induced ligand removal and patterning of ZnO nanoparticles: from semiconducting films towards printed electronics

In this manuscript we present a new approach for the fabrication of ZnO nanoparticle based semiconducting thin films. The films are obtained by spin coating of stable nanoparticle dispersions with low boiling point ligands. As the ligands might hinder efficient charge transport between the particles in electronic devices, we present a method to remove them by a vacuum-induced "sintering" process of the particles at room temperature. Airline stabilized ZnO nanoparticles were obtained by the decomposition of diethylzinc (Et2Zn) in the presence of amines. If butylamine is used as the ligand, NMR and XPS measurements show that complete removal of butylamine can be achieved by storing the nanoparticles in vacuum overnight. Ligand removal leads to electronic interparticle contact as measured with field effect transistors. The ability to process at room temperature makes this approach highly interesting for temperature-sensitive substrates. The potential of our approach for printed electronics is further shown by patterning nanoparticle dispersions via micro-injection Moulding in capillaries Lis a soft lithographic method.