羟氨苄青霉素引起大疱性类天疱疮样疹

High concentrations of defects are introduced into nanoscale ZnO through non-equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420 nm (2.95 eV < Eg = 3.26 eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488 nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial-zinc-related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as-prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co-emission of blue and green emissions and peak adjustment from blue to yellow.

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Blue Luminescence of ZnO Nanoparticles Based on Non‐Equilibrium Processes: Defect Origins and Emission Controls

ZnO nanostructures for optoelectronics: Material properties and device applications

A common misconception is that the irradiation of solids with energetic electrons and ions has exclusively detrimental effects on the properties of target materials. In addition to the well-known cases of doping of bulk semiconductors and ion beam nitriding of steels, recent experiments show that irradiation can also have beneficial effects on nanostructured systems. Electron or ion beams may serve as tools to synthesize nanoclusters and nanowires, change their morphology in a controllable manner, and tailor their mechanical, electronic, and even magnetic properties. Harnessing irradiation as a tool for modifying material properties at the nanoscale requires having the full microscopic picture of defect production and annealing in nanotargets. In this article, we review recent progress in the understanding of effects of irradiation on various zero-dimensional and one-dimensional nanoscale systems, such as semiconductor and metal nanoclusters and nanowires, nanotubes, and fullerenes. We also consider the t...

Ion and electron irradiation-induced effects in nanostructured materials

I will overview our recent results on ultra-long lasers and will discuss the concept of a fiber laser with an open cavity that operates using random distributed feedback provided by Rayleigh scattering amplified through the Raman effect.

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Random distributed feedback fiber laser

The research on ZnO has a long history but experiences an extremely vivid revival during the last 10 years. We critically discuss in this didactical review old and new results concentrating on optical properties but presenting shortly also a few aspects of other fields like transport or magnetic properties. We start generally with the properties of bulk samples, proceed then to epitaxial layers and nanorods, which have in many respects properties identical to bulk samples and end in several cases with data on quantum wells or nano crystallites. Since it is a didactical review, we present explicitly misconceptions found frequently in submitted or published papers, with the aim to help young scientists entering this field to improve the quality of their submitted manuscripts. We finish with an appendix on quasi two- and one-dimensional exciton cavity polaritons.

65 years of ZnO research – old and very recent results

Recent theoretical work on random lasing predicts that the occurrence of narrow lasing spikes can be caused by both localized and extended modes of light1,2,3. Typical random lasing spikes have been observed in powders of zinc oxide nanoparticles4, but identifying the possible degrees of localization of such modes has until now been an open issue5. In this Letter we present an experimental procedure that directly extracts the area of localization of the modes. This method relies on the investigation of micro-structured fields of zinc oxide powder, which also allows direct correlation to the local structural properties of the ensemble of subwavelength particles by scanning electron microscopy. We find that lasing from both localized and extended modes can be observed simultaneously. Our observation also corroborates the prediction that localized modes have a lower loss rate than that of extended modes5. Whether the electromagnetic fields in random lasers are localized or extended is a topic of ongoing debate. Now, the localization of modes in micro-structured ZnO powder is experimentally determined and lasing from both kinds of modes (localized and extended) shown to exist simultaneously.

Co-existence of strongly and weakly localized random laser modes

Using indium as catalyst for growth and simultaneously as doping source, ordered arrays of n-type ZnO single crystal nanorods have been perpendicularly grown on p-GaN∕Al2O3 substrates with a vapor phase transport growth method. The low temperature photoluminescence measurements of the n-ZnO nanorods show dominant In-related neutral donor bound exciton emission in the ultraviolet region. Electrical transport measurements performed on single n-ZnO nanorods yield resistances of about 50–200kΩ and a typical specific resistivity of 2.0×10−2Ωcm. The resistivity is one order of magnitude reduced by introducing In compared to the nominally undoped ZnO nanorods.

Ordered n-type ZnO nanorod arrays

Inside Back Cover (Phys. Status Solidi B 6/2010)

In this work we examine the lasing properties of single ZnO nanorods under ns- and fs-pulsed excitation. By measuring the photoluminescence of individual nanorods excited by a single ns-pulse we demonstrate that several stable lasing modes are emitted by the nanorod. In this quasi-stationary excitation regime lasing up to room temperature can be achieved. Measurements of the temperature dependent laser threshold and of the spectral lasing region are presented. The excitation with fs-pulsed excitation combined with a time resolved photoluminescence measurement gives furthermore an insight in the lasing dynamics. Scanning electron microscope picture of a sample with an array of ZnO nanorods grown perpendicular aligned on the substrate.

Janos Sartor

Papers

65 years of ZnO research – old and very recent results

Co-existence of strongly and weakly localized random laser modes

Ordered n-type ZnO nanorod arrays

Inside Back Cover (Phys. Status Solidi B 6/2010)

Lasing in single ZnO nanorods after fs‐ and ns‐pulsed excitation