Effect of Size-Dependent Thermal Instability on Synthesis of Zn(2) SiO(4)-SiO(x) Core–Shell Nanotube Arrays and Their Cathodoluminescence Properties

Vertically aligned Zn(2)SiO(4)-SiO(x)(x < 2) core–shell nanotube arrays consisting of Zn(2)SiO(4)-nanoparticle chains encapsulated into SiO(x) nanotubes and SiO(x)-coated Zn(2)SiO(4) coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW) arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of “etching” to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn(2)SiO(4)-SiO(x) coaxial nanotubes, single-crystalline Zn(2)SiO(4)-nanoparticle-chain-embedded SiO(x) nanotubes, and single-crystalline Zn(2)SiO(4)-SiO(x) coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL) spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn(2)SiO(4) phase.