Hot carriers generated
from the nonradiative decay of localized
surface plasmons are capable of driving charge-transfer reactions
at the surfaces of metal nanostructures. Photocatalytic devices utilizing
plasmonic hot carriers are often based on metal nanoparticle/semiconductor
heterostructures owing to their efficient electron–hole separation
ability. The rapid thermalization of hot carriers generated at the
metal nanoparticles yields a distribution of carrier energies that
determines the capability of the photocatalytic device to drive redox
reactions. Here, we quantify the thermalized hot carrier energy distribution
generated at Au/TiO2 nanostructures using wavelength-dependent
scanning electrochemical microscopy and a series of molecular probes
with different redox potentials. We determine the quantum efficiencies
and oxidizing power of the hot carriers from wavelength-dependent
reaction rates and photocurrent across the metal/semiconductor interface.
The wavelength-dependent reaction efficiency tracks the surface plasmon
resonance spectrum of the Au nanoparticles, showing that the reaction
is facilitated by plasmon excitation, while the responses from molecules
with different redox potentials shed light on the energy distribution
of the hot holes generated at metal nanoparticle/semiconductor heterostructures.
The results provide important insight into the energies of the plasmon-generated
hot carriers and quantum efficiencies of plasmonic photocatalytic
devices.
We have studied the current-carrying capability of high quality epitaxial MgB2 films synthesized using the hybrid physical-chemical vapor deposition technique by both transport measurement in nanobridge constrictions and magnetization measurement. An extremely high self-field critical current density Jc(0)>108A∕cm2, approaching the theoretical depairing current of MgB2, was observed on a 150nm bridge, indicating an excellent current-carrying capability in these films. The magnetization measurement also showed very high Jc.
We demonstrate a novel pathway to control and stabilize oxygen vacancies in complex transition-metal oxide thin films. Using atomic layer-by-layer pulsed laser deposition (PLD) from two separate targets, we synthesize high-quality singlecrystalline CaMnO 3 films with systematically varying oxygen vacancy defect formation energies as controlled by coherent tensile strain. The systematic increase of the oxygen vacancy content in CaMnO 3 as a function of applied in-plane strain is observed and confirmed experimentally using high-resolution soft X-ray absorption spectroscopy (XAS) in conjunction with bulk-sensitive hard X-ray photoemission spectroscopy (HAXPES). The relevant defect states in the densities of states are identified and the vacancy content in the films quantified using the combination of first-principles theory and core−hole multiplet calculations with holistic fitting. Our findings open up a promising avenue for designing and controlling new ionically active properties and functionalities of complex transition-metal oxides via strain-induced oxygen-vacancy formation and ordering.
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