Growth dynamics of ZnO nanowire on a fiber-tip air bubble

We demonstrate a novel method of online monitoring of ZnO nanowire growth by an optical method. Nanowires were grown on the surface of an optical fiber tip and their effect on the spectral characteristics of a fiber-tip Fabry-Perot interferometer (FPI) was investigated. The interference fringe of the fiber tip yielded a linear red shift against the ZnO nanowire growth. Results also indicated that the ZnO thin layer has a stronger correlation with the reflection spectra variation of the FPI than the ZnO nanowires. The growth rate of the ZnO thin layer was measured by monitoring the free spectral range (FSR) of the reflection spectra, which achieved growth rates of 2 nm/min from 40 to 100 min and approximately 1.1 nm/min from 100 to 120 min in a 0.01-M growth solution, and 6.8 nm/min from 40 to 90 min in a 0.05-M growth solution. The proposed method is simple and cost effective, and has potential for wider applications in nanostructure manufacturing.