Optical and magnetic characterization of transition metal ion doped ZnO microspheres synthesized via laser ablation in air
TL;DR: In this paper, the synthesis of transition metal doped (TM) ZnO micropsheres using doped znO sintered targets containing Mn 1% dopant was reported.
Abstract: We report the synthesis of transition metal doped (TM) ZnO micropsheres using doped ZnO sintered targets containing Mn 1% dopant. Transition metals are prospective materials for p type acceptor doping in ZnO. Structural and morphology study were conducted using XRD (X-ray diffraction), SEM and Raman spectroscopy. Room temperature Photoluminescence (PL) spectra of the fabricated ZnO microspheres were measured, at an excitation wavelength of 355 nm. In our study, smooth spherical shaped micro particles with different diameters ranging from ~1 to 3 μm were grown in different substrates by using a pulsed N 3+: YAG laser. SEM (Scanning Electron Microscopy) images show the presence of uniform smooth surfaced spheres. Raman scattering measurements from the synthesised samples at 532 nm wavelength excitation provide confirms the wurtzite structure of the fabricated undoped and TM doped ZnO microsphere. The doped microspheres exhibited UV whispering gallery modes (WGM) cavity lasing by optical pumping. Magnetic measurements from TM doped ZnO microparticles using vibrating sample magnetometer (VSM) are in progress.
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TL;DR: In this article, the surface optical modes in cylindrical ZnO nanoparticles have been studied theoretically using a dielectric continuum model and experimentally by Raman spectrometry.
Abstract: Surface optical modes in cylindrical ZnO nanoparticles have been studied theoretically using a dielectric continuum model and experimentally by Raman spectrometry. Theoretically, both wave vector dispersion and outer medium dielectric constant effects have been investigated. Consequently, we attribute the intense peak at $490\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ in the Raman experiment to a surface optical mode related to the top basis of the nanoparticles. We deduce that the bonding of long alkyl chain amines is likely related to the lateral surface of the nanoparticles.
54 citations
TL;DR: In this paper, a facile two-step solution route is demonstrated for the fabrication of Co-doped ZnO nanorods with diverse doping levels, which can be attributed to the sp−d exchange interactions between the electrons in the conduction band of ZnOs and the localized d electrons of the Co2+ cations.
53 citations
TL;DR: In this paper, a zinc oxide (ZnO) micro/nanosphere crystal was fabricated by simply ablating a ZnO sintered target, which was much more productive method without any time-consuming crystal growth process.
Abstract: We report ultraviolet (UV) whispering-gallery-mode (WGM) lasing in a zinc oxide (ZnO) micro/nanosphere crystal fabricated by simply ablating a ZnO sintered target, which was much more productive method without any time-consuming crystal-growth process. The lasing spectral mode spacing was controlled by changing the diameters, and single-mode lasing was realized from a ZnO nanosphere. Experimental results were in good agreement with predictions from WGM theories. Since the ZnO sphere can operate as an active WGM refractometric sensor for small molecules in UV region, high sensitivity enhanced by high quality factor, refractive index, and wavelength dispersion can be expected.
43 citations
TL;DR: The fabrication of single-crystalline semiconductor microspheres that have surfaces with atomic-level smoothness are reported, which opens a pathway for studying the hidden mechanism of anisotropy-free crystal growth and its applications.
Abstract: Microspheres with high sphericity exhibit unique functionalities. In particular, their high symmetry makes them excellent omnidirectional optical resonators. As such perfect micrometre-sized spheres are known to be formed by surface tension, melt cooling is a popular method for fabricating microspheres. However, it is extremely difficult to produce crystalline microspheres using this method because their surfaces are normally faceted. Only microspheres of polymers, glass, or ceramics have been available, while single-crystalline microspheres, which should be useful in optical applications, have been awaiting successful production. Here we report the fabrication of single-crystalline semiconductor microspheres that have surfaces with atomic-level smoothness. These microspheres were formed by performing laser ablation in superfluid helium to create and moderately cool a melt of the anisotropic semiconductor material. This novel method provides cooling conditions that are exceptionally suited for the fabrication of single-crystalline microspheres. This finding opens a pathway for studying the hidden mechanism of anisotropy-free crystal growth and its applications.
41 citations
TL;DR: The comparison between theoretical analysis and experiment suggests that the dielectric constant of the ZnO microsphere is somewhat different from that for bulk ZnN, and the sharp resonances of whispering gallery modes in zinc oxide microspheres cover the entire visible window.
Abstract: A detailed study on the optical cavity modes of zinc oxide microspheres under the optical excitation is presented. The zinc oxide microspheres with diameters ranging from 1.5 to 3.0 µm are prepared using hydrothermal growth technique. The photoluminescence measurement of a single microsphere shows prominent resonances of whispering gallery modes at room temperature. The experimentally observed whispering gallery modes in the photoluminescence spectrum are compared with theoretical calculations using analytical and finite element methods in order to clarify resonance properties of these modes. The comparison between theoretical analysis and experiment suggests that the dielectric constant of the ZnO microsphere is somewhat different from that for bulk ZnO. The sharp resonances of whispering gallery modes in zinc oxide microspheres cover the entire visible window. They may be utilized in realizations of optical resonators, light emitting devices, and lasers for future chip integrations with micro/nano optoelectronic circuits, and developments of optical biosensors.
40 citations