We report a new method to fabricate electrode-embedded multiple nanopore structures with sub-10 nm diameter, which is designed for electrofluidic applications such as ionic field effect transistors. Our method involves patterning pore structures on membranes using e-beam lithography and shrinking the pore diameter by a self-limiting atomic layer deposition process. We demonstrate that 70-80 nm diameter pores can be shrunk down to sub-10 nm diameter and that the ionic transport of KCl electrolyte can be efficiently manipulated by the embedded electrode within the membrane.

The manipulation of radiative properties of light emitters coupled with surface plasmons is important for engineering new nanoscale optoelectronic devices, including lasers, detectors and single photon emitters. However, so far the radiative rates of excited states in semiconductors and molecular systems have been enhanced only moderately, typically by a factor of 10-50, producing emission mostly from thermalized excitons. Here, we show the generation of dominant hot-exciton emission, that is, luminescence from non-thermalized excitons that are enhanced by the highly concentrated electromagnetic fields supported by the resonant whispering-gallery plasmonic nanocavities of CdS-SiO(2)-Ag core-shell nanowire devices. By tuning the plasmonic cavity size to match the whispering-gallery resonances, an almost complete transition from thermalized exciton to hot-exciton emission can be achieved, which reflects exceptionally high radiative rate enhancement of >10(3) and sub-picosecond lifetimes. Core-shell plasmonic nanowires are an ideal test bed for studying and controlling strong plasmon-exciton interaction at the nanoscale and opens new avenues for applications in ultrafast nanophotonic devices.

Inorganic zero-dimensional perovskites, such as Cs4PbBr6, offer an underexplored opportunity to achieve efficient exciton formation and radiative recombination. In particular, the origin of sub-bandgap green emission from Cs4PbBr6 is not well understood. Herein, we develop a sequential deposition approach to growing highly smooth Cs4PbBr6 films with low rms roughness of 8.15 nm by thermal evaporation. We find that the films have an excitonic absorption edge at 3.9 eV, but exhibit sub-bandgap photoluminescence at 2.4 eV, with a photoluminescence quantum yield as high as 55 ± 2%. We analyze the origin of this sub-bandgap photoluminescence through in-depth transmission electron microscopy, selective area electron diffraction, energy-dispersive X-ray spectrometry, photothermal deflection spectroscopy, and photoluminescence. From these measurements, we find that the Cs4PbBr6 contains residual CsPbBr3, and the wider bandgap Cs4PbBr6 confines the excitons in the CsPbBr3, enabling high photoluminescence quantum yields. We use this material as the active layer in light-emitting diodes, achieving an improved external quantum efficiency of 0.36%, a significant improvement over the CsPbBr3 control devices with EQEs up to 0.0062%.

Heavy-alkali post-deposition treatments (PDTs) utilizing Cs or Rb has become an indispensable step in producing high-performance Cu(In,Ga)Se 2 (CIGS) solar cells. However, full understanding of the mechanism behind the improvements of device performance by heavyalkali treatments, particularly in terms of potential modification of defect characteristics, has not been reached yet. Here, we present an extensive study on the effects of CsF-PDT on material properties of CIGS absorbers and the performance of the final solar devices. Incorporation of an optimized concentration of Cs into CIGS resulted in a significant improvement of the device efficiency from 15.9 to 18.4% mainly due to an increase in the open-circuit voltage by 50 mV. Strong segregation of Cs at the front and rear interfaces as well as along grain boundaries of CIGS was observed via high-resolution chemical analysis such as atomic probe tomography. The study of defect chemistry using photoluminescence and capacitance-based measurements revealed that both deep-level donor-like defects such as V Se and In Cu and deep-level acceptor-like defects such as V In or Cu In are passivated by CsF-PDT, which contribute to an increased hole concentration. Additionally, it was found that CsF-PDT induces a slight change in the energetics of V Cu , the most dominant point defect that is responsible for the p-type conductivity of CIGS.

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We report on a novel fabrication method of a nanochannel ionic field effect transistor (IFET) structure with sub-10-nm dimensions. A self-sealing and self-limiting atomic layer deposition (ALD) facilitates the fabrication of lateral type nanochannels smaller than the e-beam or optical lithographic limits. Using highly conformal ALD film structures, including TiO(2), TiO(2)/TiN, and Al(2)O(3)/Ru, we have fabricated lateral sub-10-nm nanochannels with good control over channel diameter. Nanochannels surrounded by core/shell (high-k dielectric/metal) layers give rise to all-around-gating IFETs, an important functional element in an electrofluidic-based circuit system.

The photoelectrochemical (PEC) properties of a Cu(In,Ga)Se2 (CIGS) photocathode covered with reduced graphene oxide (rGO) as a catalyst binder for solar‐driven hydrogen evolution are reported. Chemically reduced rGO with various concentrations is deposited as an adhesive interlayer between CIGS/CdS and Pt. PEC characteristics of the CIGS/CdS/rGO/Pt are improved compared to the photocathode without rGO due to enhancement of charge transfer via efficient lateral distribution of photogenerated electrons by conductive rGO to the Pt. More importantly, the introduction of rGO to the CIGS photocathode significantly enhances the PEC stability; in the absence of rGO, a rapid loss of PEC stability is observed in 2.5 h, while the optimal rGO increases the PEC stability of the CIGS photocathode for more than 7 h. Chemical and structural characterizations show that the loss of the Pt catalyst is one of the main reasons for the lack of long‐term PEC stability; the introduction of rGO, which acts as a binder to the Pt catalysts by providing anchoring sites in the rGO, results in complete conservation of the Pt and hence much enhanced stability. Multiple functionality of rGO as an adhesive interlayer, an efficient charge transport layer, a diffusion barrier, and protection layer is demonstrated.