B. Liu

Surface plasmon enhanced band edge luminescence of ZnO nanorods by capping Au nanoparticles

The author observe sixfold enhancement in the near band gap emission of ZnO nanorods by employing surface plasmon of Au nanoparticles, while the defect-related emission is completely suppressed. Time-resolved photoluminescence indicates that the decay process becomes much faster by Au capping. The remarkable enhancement of the ultraviolet emission intensities and transition rates is ascribed to the charge transfer and efficient coupling between ZnO nanorods and Au surface plasmons. The suppression of the green emission might be due to a combined effect of Au surface plasmon and passivation of the ZnO nanorod surface traps.

Atomic structure and defect densities in low dielectric constant carbon doped hydrogenated silicon oxide films, deposited by plasma-enhanced chemical vapor deposition

Results of structural characterization by Fourier transform infrared spectroscopy, x-ray diffraction, and specular x-ray reflectivity measurements are employed for the interpretation of electrical measurement data and the deconvoluted distribution of electron states, N(E) of carbon doped hydrogenated silicon oxide (SiOCH) low-k dielectric films. Atomic structure of the films is identified as a mixture of a dominant and totally amorphous SiO2-like phase with a partially polycrystalline SiC phase. The n-type dc conductivity that dominates in this material points to the principal role of the SiC-like phase in the dc transport of the SiOCH material. The deep level transient spectroscopy technique is applied for the N(E) shape studies in the energy range up to 0.7 eV below the conduction band bottom. Typical N(E) values lie in the 1010–1014u2009eV−1u200acm−3 range for films deposited at different ratios of tri-methyl-silane to oxygen flow rate. No correlation between the N(E) shape and the film deposition conditions h...

Ultraviolet light emission and excitonic fine structures in ultrathin single-crystalline indium oxide nanowires

We report the ultraviolet light emission from ultrathin indium oxide (In2O3) nanowires fabricated by the vapor-liquid-solid method. The high crystalline quality of the samples is confirmed by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Strong ultraviolet light emission is consistently observed in the temperature dependent photoluminescence measurements carried out between 10 and 300 K. Emissions related to free excitons and bound exciton complexes, donor-acceptor pair transition and its relevant longitudinal optical phonon replicas are identified and their temperature-dependent evolution is discussed in details.

Pulsed laser deposition of high-quality ZnCdO epilayers and ZnCdO/ZnO single quantum well on sapphire substrate

The authors report on high quality ZnCdO alloy epilayers and ZnCdO/ZnO single quantum well structures on sapphire substrates by pulsed laser deposition. The Cd concentration in the ZnCdO alloy can be systematically adjusted via the substrate temperature and single-phase ZnCdO alloy with a band gap at room temperature extended to 2.94 eV is achieved. The single quantum well structures exhibit strong photoluminescence from the well layer with extremely weak emission from deep level defects and the ZnO barrier, indicating the high quality of ZnCdO/ZnO single quantum well structures.

Surface-plasmon enhancement of band gap emission from ZnCdO thin films by gold particles

We present our study of the dependence of surface plasmon (SP) coupled band gap emission and defect emission on the sputtering time of gold particles on ZnCdO films. Eightfold enhancement of the band gap emission from ZnCdO thin films coated with Au particles is observed, while the defect emission is completely suppressed. The remarkable enhancement of the band gap emission is mainly attributed to the coupling between excitons in ZnCdO films and the SP of Au particles. While the suppression of the defect emission may be ascribed to a combined effect of the reduction in surface defects and the charge transfer from defect level to the Au Fermi level.

Doping-free white organic light-emitting diodes without blue molecular emitter: An unexplored approach to achieve high performance via exciplex emission

Doping-free white organic light-emitting diodes (DF-WOLEDs) are promising for the low-cost commercialization because of their simplified device structures. However, DF-WOLEDs reported thus far in the literature are based on the use of blue single molecular emitters, whose processing can represent a crucial point in device manufacture. Herein, DF-WOLEDs without the blue single molecular emitter have been demonstrated by managing a blue exciplex system. For the single-molecular-emitter (orange or yellow emitter) DF-WOLEDs, (i) a color rendering index (CRI) of 81 at 1000u2009cd/m2 can be obtained, which is one of the highest for the single-molecular-emitter WOLEDs, or (ii) a high efficiency of 35.4u2009lm/W can be yielded. For the dual-molecular-emitter (yellow/red emitters) DF-WOLED, a high CRI of 85 and low correlated color temperature of 2376u2009K at 1000u2009cd/m2 have been simultaneously achieved, which has not been reported by previous DF-WOLEDs. Such presented findings may unlock an alternative avenue to the simplif...

Surface plasmon induced exciton redistribution in ZnCdO/ZnO coaxial multiquantum-well nanowires

The authors present the surface plasmon effects of Au nanoparticles on the photoluminescence properties of ZnCdO/ZnO coaxial multiquantum-well nanowires fabricated using chemical vapor deposition and pulse laser deposition methods. The spontaneous emission rate from ZnCdO quantum wells was increased by surface plasmon coupling by 1.29 times. The strong plasmon coupling between ZnO barriers and Au nanoparticles provides an extra fast decay channel for excitons generated in ZnO barrier layer and leads to exciton redistribution in ZnCdO/ZnO coaxial quantum wells, which promotes radiative recombination in ZnO barriers but reduces the number of excitons relaxing into the ZnCdO quantum wells.

Regulating Charge and Exciton Distribution in High-Performance Hybrid White Organic Light-Emitting Diodes with n-Type Interlayer Switch

The interlayer (IL) plays a vital role in hybrid white organic light-emitting diodes (WOLEDs); however, only a negligible amount of attention has been given to n-type ILs. Herein, the n-type IL, for the first time, has been demonstrated to achieve a high efficiency, high color rendering index (CRI), and low voltage trade-off. The device exhibits a maximum total efficiency of 41.5xa0lmxa0W−1, the highest among hybrid WOLEDs with n-type ILs. In addition, high CRIs (80–88) at practical luminances (≥1000xa0cdxa0m−2) have been obtained, satisfying the demand for indoor lighting. Remarkably, a CRI of 88 is the highest among hybrid WOLEDs. Moreover, the device exhibits low voltages, with a turn-on voltage of only 2.5xa0V (>1xa0cdxa0m−2), which is the lowest among hybrid WOLEDs. The intrinsic working mechanism of the device has also been explored; in particular, the role of n-type ILs in regulating the distribution of charges and excitons has been unveiled. The findings demonstrate that the introduction of n-type ILs is effective in developing high-performance hybrid WOLEDs.

Temperature dependence of weak localization effects of excitons in ZnCdO/ZnO single quantum well

We report on the optical properties of high-quanlity ZnCdO/ZnO single quantum well (SQW) grown on c-sapphire substrates by pulsed laser deposition. The temperature dependent photoluminescence (PL) of ZnO/ZnCdO SQWs exhibits an inconspicuous S-shaped property due to the weak carrier localization effect, as a consequence of the slightly inhomogeneous Cd distribution in the well layer as well as the smooth interfaces. The integrated PL intensity of the higher Cd SQW decreases faster than that of the lower sample with increasing temperature, indicating the presence of interface barrier in high Cd content SQWs.