In this work, a novel approach is suggested to grow bilayer fibers by combining electrospinning and atomic layer deposition (ALD). Polyvinyl alcohol (PVA) fibers are obtained by electrospinning and subsequently covered with thin Al2O3 deposited at a low temperature by ALD. To burn the PVA core, the fibrous structures are subjected to high-temperature annealing. Differential scanning calorimetry (DSC) analysis of the PVA mat is performed to establish the proper annealing regime for burning off the PVA core and obtaining hollow fibers. The hollow fibers thus formed are covered with a ZnO layer deposited by ALD at a higher temperature within the ALD window of ZnO. This procedure allows us to prepare ZnO films with better crystallinity and stoichiometry. Different characterization methods-SEM, ellipsometry, XRD, and XPS-are performed at each step to investigate the processes in detail.
Keywords: ZnO; atomic layer deposition (ALD); electrospinning; high-aspect-ratio (HAR) nanostructures; polyvinyl alcohol (PVA).