Pulsed laser assisted growth of aligned nanowires of WO3: role of interface with substrate

Abstract

We report here a systematic study of the growth of aligned WO₃ (002)-oriented nanowires (NWs) on a (111)-oriented platinised silicon substrate using a pulsed laser deposition (PLD) method. Transmission electron microscopy (TEM) analysis has shown that the wires are single crystalline and grow along the [001]_t or [100]_t directions. X-ray diffraction (XRD) measurements confirm phase and structural analysis. We investigated the effect of ablated particle flux on nanowire growth, in particular, the role of the nucleating centre at the interface as it gets modified by the ablated particle flux. We observe a critical value of the laser energy (that determines a critical flux and energy of ablated moieties) at which a compact nanograin film gets converted to an aligned nanowire film. We attribute the existence of such a threshold to the desorption process from the catalyst droplet. By cross-sectional TEM and compositional mapping accompanied by simulation, we confirm that the interfacial layer between the substrate and NW is modified by the ablated particle flux and energy. Aligned NWs above the threshold energy can be attributed to the formation of favorable nucleation sites for a preferred orientation.