Optical emission and absorption spectra of Zn–ZnO core-shell nanostructures

Abstract

The core-shell Zn-ZnO nanostructures were fabricated from Zn-powder embedded in graphite (i.e. carbon matrix) in a thin-films form by an inexpensive vacuum arc technique followed by laser ablation. The grazing incidence X-ray diffraction pattern shows that intensity of Zn-peak decreases, and subtle ZnOpeak increasing with the increase in laser power. The high resolution transmission electron microscopic study clearly exhibits the formation of a core-shell nanostructure as fabricated by laser ablation. The emission characteristics of laser ablated (with different powers) samples show a strong exciton peak at 388 nm, and a few more weak peaks (due to weak defect states in the visible range). The optical absorption spectra were obtained from the excitonic peaks (from 344 nm to 317 nm) on decreasing laser power. These peaks occur due to the coupling of exciton absorption (from ZnO shell layer) and core metal interband absorption. The Zn-ZnO core-shell nanostructure is useful for nanophotonic applications.

Visible and UV photo-detection in ZnO nanostructured thin films via simple tuning of solution method

“…The first transition ( → VB ) occurs due to the formation of unstable state of by capturing electrons form CB 38 . This unstable state, when recombine with photoexcited hole in the VB , would generate green emission around 530 nm 39 . The second transition CB → also has a strong possibility as the exciting energy is enough to pump the electrons to CB that after falling to will give rise a green emission at 530 nm.…”

“…In the photovoltage measurements, rise time is the time required in 90% rise of photovoltage form its initial value (after switching ON the illumination), and fall time is the time taken in the falling of maximum photovoltage to 10% (after switching ‘OFF’ the illumination) 53 . For each photodetector, the period of ON and OFF time was taken different by considering their response time as different, and also to eliminate the heating effects on the sample surface 39 , 54 . In the experiments, the ON and OFF time was controlled using a camera shutter.…”

Effect of Zn Addition on Non-Resonant Third-Order Optical Nonlinearity of the Cu-Doped Germano-Silicate Optical Glass Fiber

“…[37][38][39] The absorption peak at 469 nm in the Cu/Zn-codoped germano-silicate optical glass fiber was due to the strong confinement effect of ZnO semiconductor particles and the peak position was shifted relative to the exciton absorption in the ZnO-doped germano-silicate optical glass fiber reported earlier (490 nm), 40 the ZnO nanorod (381 nm), 41 or the thin-film of carbon encapsulated Zn-ZnO nanoparticles (344 nm). 42 Earlier, the shift of optical absorption peak was also observed from the nano-particles embedded in the silica matrix due to quantum size effect. [42][43][44][45] It is noted that the Cu/Zn-codoped germano-silicate optical glass fiber has low transmission loss at the second optical communication window of 1550 nm because of converting Cu 2+ ions to Cu metal particles by providing reduction condition (Cu 2+ +Zn → Cu+Zn 2+ due to high ionization tendency of Zn as a reduction agent during the fiber fabrication process.…”

“…42 Earlier, the shift of optical absorption peak was also observed from the nano-particles embedded in the silica matrix due to quantum size effect. [42][43][44][45] It is noted that the Cu/Zn-codoped germano-silicate optical glass fiber has low transmission loss at the second optical communication window of 1550 nm because of converting Cu 2+ ions to Cu metal particles by providing reduction condition (Cu 2+ +Zn → Cu+Zn 2+ due to high ionization tendency of Zn as a reduction agent during the fiber fabrication process. The intensity of the absorption at 435 nm (after baseline correction) due to Cu metal particles of the Cu/Zn-codoped germano-silicate optical glass fiber was about 0.013 cm −1 , larger than that of the Cudoped germano-silicate optical glass fiber (0.005 cm −1 at 445 nm).…”

Influence of Elastic and Surface Strains on the Optical Properties of Semiconducting Core-Shell Nanoparticles

“…[25,26] In the course of these investigations, it was realized that such nanostructures display significant deviations from the optical properties of their bulk constituent components -including the measured values of their band gaps E g . [17,27,28,31,34,40,41] Although quantum confinement effects that become important on the length scale of few nm are expected to affect the E g , deviations from bulk behavior were found even in CSNPs that are too large to operate in the quantum confinement regime.…”