One-Step Low-Temperature Synthesis of Syringe-Shaped ZnO Nanorod Arrays, Growth Mechanism and Optical Properties

The syringe-shaped ZnO nanorod arrays (ZNAs) are synthesized by one-step aqueous solution method. The SiNx/Si substrate with this structure exhibits rather lower surface reflectance over a wide range of wavelengths than the samples without it or with round top ZNAs. The theoretical reflectance simulated by three-dimensional finite-difference time-domain method also reveals that the ZnO nanorods with ultrasharp tips can effectively suppress the surface reflectance, which attributes to the effective refractive index gradual increasing from air to the bottom of syringe-shaped ZNAs. Also, from the room-temperature PL spectra, the UV emission peak is found at around 380 nm, and the intensity is much higher than other two broad visible peaks (at around 460 nm and 540 nm respectively), indicating ZNAs synthesized in solution have high crystal quality. Furthermore, the possible growth mechanism of syringe-shaped ZNAs is proposed.