Zn_2GeO_4/SnO_2 nanowire heterostructures driven by plateau-rayleigh instability

Abstract

Herein, we report the formation of a particular core-shell structure, with a zinc germanate (Zn_2GeO_4) nanowire core and a discontinuous shell of SnO_2 nanocrystals, obtained in a single-step process. We propose a growth model that combines the Plateau-Rayleigh mechanism to produce a pattern of amorphous germanium oxide (a-GeO_2) particles along the Zn_2GeO_4 nanowire and the subsequent growth of well-faceted SnO_2 crystals when the nanowire orientation meets good lattice matching conditions. In this latter case, the linear array of a-GeO_2 particles acts as nucleation sites for the SnO_2 crystallites, leading to a skewer-like morphology that retains the periodicity of the Plateau-Rayleigh process. Otherwise, nanowires with different orientations appear decorated with a pattern of a-GeO_2 beads mimicking a necklace. Atomic resolution electron microscopy has been used to characterize the Zn_2GeO_4/SnO_2 nanoheterostructures. In addition, optical confinement effects have been observed in the luminescence maps and spectra, which have potential for further exploitation in the design of optical microcavities.