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Abstract We investigate the fluorescence from submonolayer rhodamine 6G molecules near gold nanoparticles (NPs) at a well-controlled poly (methyl methacrylate) (PMMA) interval thickness from 1.5 to 21 nm. The plasmonic resonance peaks of gold NPs are tuned from 530 to 580 nm by the PMMA spacer of different thicknesses. Then, due to the plasmonic resonant excitation enhancement, the emission intensity of rhodamine 6G molecules at 562 nm is found to be enhanced and shows a decline as the PMMA spacer thickness increases. The variation of spectral intensity simulated by finite-difference time-domain method is consistent with the experimental results. Moreover, the lifetime results show the combined effects to rhodamine 6G fluorescence, which include the quenching effect, the barrier effect of PMMA as spacer layer and the attenuation effect of PMMA films.

High-index dielectrics have recently been regarded as promising building blocks in nanophotonics owing to optical electric and magnetic Mie resonances. In particular, silicon is gaining great interest as the backbone of modern technology. Here, silicon dimer nanocavities with different sizes of silicon nanospheres were constructed using a probe nanomanipulation method and interacted with a few-layered R6G membrane to investigate the enhancement of electric and magnetic mode coupling. The evidence of the enhancement of fluorescence and slightly prolonged lifetime of R6G indicated the existence of nanocavities. In addition, the simulated electric and magnetic field distributions and decomposed mode of nanocavity were used to analyze the contribution of electric and magnetic modes to the R6G enhanced fluorescence. Such silicon dimer is a flexible nanocavity with electric and magnetic mode enhancement and has promising applications in sensing and all-dielectric metamaterials or nanophotonic devices.

The steady-state spectra and fluorescence lifetimes are investigated under vacuum for methylammonium lead bromide and iodide (CH3NH3PbBr3 or MAPbBr3, and CH3NH3PbI3 or MAPbI3) thin films by stably controlling the sample temperature in the range of 78 K to 320 K. The transformation of spectrum features and lifetime components are proved to be quite sensitive to the temperatures in accordance with the phase transition of structures. Our work demonstrates that the halide anions I- and Br- lead to remarkable differences on optical characteristics. Due to the distinct behaviors of excitons, electron-hole pairs and free carriers in decay channels, MAPbI3 has much longer lifetime and higher low-temperature fluorescence efficiency than those of MAPbBr3. The findings provide possible choices for certain perovskites under various ambient temperature conditions to display photovoltaic or luminescent advantage.

With the demand for increasing storage density in spintronic applications, extensive work has been devoted to searching for perpendicular magnetic material systems with strong exchange bias effect. In this study we have investigated the exchange bias effect in perpendicular magnetized heterostructures of [Co/Ni]N/(Cu, Ta)/TbCo. An interlayer of 0.8 nm Cu is capable of achieving separate magnetization switching, showing a quite large exchange bias field over 2.9 kOe. With increasing the interlayer thickness, both the Co/Ni bias field and TbCo switching field decrease much more rapidly for the samples with a Ta interlayer as compared to the Cu case, due to the better coverage ability of the amorphous nature. The influence of layer thickness and composition of the FM and FI layers has also been investigated and the variation tendencies are well interpreted.

The photoluminescence (PL) variations of organic-inorganic hybrid lead halide perovskites in different atmospheres are well documented, while the fundamental mechanism still lacks comprehensive understandings. This study reports the reversible optical and electrical properties of methylammonium lead bromide (MAPbBr3 or CH3NH3PbBr3) single crystals caused by air infiltration. With the change in the surrounding atmosphere from air to vacuum, the PL intensity of perovskite single crystals decreases, while the conductivity increases. By means of first-principles computational studies, the shallow trap states are considered as key elements in PL and conductivity changes. These results have important implications for the characterization and application of organic-inorganic hybrid lead halide perovskites in vacuum. [ABSTRACT FROM AUTHOR]

With the demand for increasing storage density in spintronic applications, extensive work has been devoted to searching for perpendicular magnetic material systems with strong exchange bias effect. In this study we have investigated the exchange bias effect in perpendicular magnetized heterostructures of [Co/Ni]N/(Cu, Ta)/TbCo. An interlayer of 0.8 nm Cu is capable of achieving separate magnetization switching, showing a quite large exchange bias field over 2.9 kOe. With increasing the interlayer thickness, both the Co/Ni bias field and TbCo switching field decrease much more rapidly for the samples with a Ta interlayer as compared to the Cu case, due to the better coverage ability of the amorphous nature. The influence of layer thickness and composition of the FM and FI layers has also been investigated and the variation tendencies are well interpreted. [ABSTRACT FROM AUTHOR]

The initial stage of pore formation and the growth process in anodic aluminum oxide (AAO) template have been carefully investigated. Detailed features are found concerning the nanostructure configuration formed on the electropolished aluminum foil and the additional fine structures in the first and second anodization resulting from the current limitation effect during the beginning time of about 2 s. It sheds new light onto the mechanism of the pore-organizing process of AAO templates. [ABSTRACT FROM AUTHOR]

The dependence of magnetic properties on layer repetition number and Ru thicknesses have been studied for perpendicularly magnetized synthetic antiferromagnet (SAF) in a structure of [Co/Ni]N/Ru/[Co/Ni]3. The optimum SAF with strong antiferromangetic coupling field and large switching field of the net magnetization have been determined and utilized as the reference layer in the pseudo spin valves. Compared with the rapid drop of GMR signal for the normal [Co/Ni]-based pseudo spin valves after annealing at low temperature (Ta) of 150°C, the spin valve with SAF reference layer exhibits much stable thermal stability due to the large switching field difference between the free and reference layers which avoids the simultaneous magnetization rotation. The GMR signal of the SAF spin valve sample is 6.0% at room temperature, it decreases very gradually with the increase of Ta. We attribute the slow GMR reduction observed in the SAF spin valve to the effects of domain formation and perpendicular anisotropy deterioration caused by high temperature anneals. [ABSTRACT FROM AUTHOR]

Laser induced magnetization dynamic behaviors of SmxFe1–x thin films with tunable x (0.25 ≤ x ≤ 0.5) are investigated by the time-resolved magneto-optical Kerr effect. It is found that the demagnetization process is accomplished by a two-stage process, the demagnetization time of stage I is within 1.0 ps (t1) for all the samples with different x, while it increases from 0 to 16 ps at stage II (t2) due to the reduced exchange coupling. By introducing an additional magneto-elastic energy contribution, the dispersion relation of precession frequency is deduced, by which the field-dependent frequency curves are well fitted. [ABSTRACT FROM AUTHOR]