Fabrication of the microtube and its typical PL spectra. (a) Schematic diagram of the cross-sectional view of the microtube after HfO2 coating (left panel). The inset indicates the multilayer structure of the tube wall. The right panel shows the optical microscope image of a microtube with coating of 150 HfO2 MLs. (b) AFM images of the flat Y2O3/ZrO2 nanomembranes with (left panel) and without (right panel) coating of 150 HfO2 MLs. (c) Typical PL spectra collected from the center spot of the microtube with different HfO2 coatings (0 to 150 MLs with a step of 10 MLs). The marked (asterisk) modes' azimuthal numbers are m = 70.
Zhong et al. Nanoscale Research Letters 2013 8:531 doi:10.1186/1556-276X-8-531