EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

A great deal of interest has been directed towards the design of new devices using 1D semiconductor nanostructures such as nanowires and nanorods (NRs). While the growth from the vapor phase has been thoroughly investigated, the growth from solutions has received much less attention, and its technology mostly relies on empirical results. We take a critical look at the research progress in the growth of ZnO NRs from solutions. We show that in conventional batch reactors the solution supersaturation varies with time. The growth rate of ZnO NRs is thus not constant over time and decreases as the growth proceeds due to the depletion of the solution in reactants [1]. The variation of the supersaturation and of the growth rate results in the variation of incorporation of dopants, impurities, and structural defects along the NRs. Moreover, with a different level of supersaturation, the growth mechanism can be altered. To precisely control the supersaturation, we employ continuous-flow reactors and discuss their design. We further point out key chemical and physical phenomena taking place during the growth and propose approaches to model them. To deeply understand the nucleation and growth phenomena, we developed lithographic techniques using focused electron and ion beams, which allow us to prepare highly uniform arrays of upright-standing ZnO NRs on different substrates and seed layers. Finally, we demonstrate methods of how individual nanorods and their heterojunctions can be electrically characterized with a nanoprobe installed in the scanning electron microscope [2].
[1] O. Černohorský, J. Grym, et al, Modeling of Solution Growth of ZnO Hexagonal Nanorod Arrays in Batch Reactors. Crystal Growth & Design, 20, 3347 (2020).
[2] S. Tiagulskyi, R. Yatskiv, H. Faitová, Š. Kučerová, D. Roesel, J. Grym, J. Veselý, "Highly Rectifying Heterojunctions Formed by Annealed ZnO Nanorods on GaN Substrates," Nanomaterials 10 (3), 508 (2020).