A study of tungsten oxide nanowires self-organized on mica support

摘要

Self-organized straight nanowires of WO_3have been epitaxially grown on muscovite mica inlow super-saturation conditions. Morphology, structure and chemical composition of theprepared nanostructures have been investigated by scanning electron microscopy (SEM), x-raydiffraction (XRD) and x-ray photoelectron spectroscopy (XPS). SEM permits us to observenanowire networks and substrate electron channeling patterns (ECP) simultaneously and thus todetermine crystallographic direction of nanowire growth. The experimental results show thatstraight WO3 nanowires are orientated preferentially parallel to two of three high symmetrycrystallographic directions of mica [100] and [110] or [100] and [110]. XRD and XPSmeasurements indicated self-assembly of very thin nanowires of hexagonal tungsten bronze inthe first stage of growth followed by the formation of stoichiometric WO_3. The growthmechanism has been studied as a function of different preparation conditions with special focuson the role of potassium ions present on the mica surface. Based on obtained results a growthmodel of tungsten oxide nanowires on mica is proposed.