Abstract
We show cathodoluminescence-based time-resolved electron beam spectroscopy in order to directly probe the spontaneous emission decay rate that is modified by the local density of states in a nanoscale environment. In contrast to dedicated laser-triggered electron-microscopy setups, we use commercial hardware in a standard SEM, which allows us to easily switch from pulsed to continuous operation of the SEM. Electron pulses of 80-90 ps duration are generated by conjugate blanking of a high-brightness electron beam, which allows probing emitters within a large range of decay rates. Moreover, we simultaneously attain a resolution better than λ/10, which ensures details at deep-subwavelength scales can be retrieved. As a proof-of-principle, we employ the pulsed electron beam to spatially measure excited-state lifetime modifications in a phosphor material across the edge of an aluminum half-plane, coated on top of the phosphor. The measured emission dynamics can be directly related to the structure of the sample by recording photon arrival histograms together with the secondary-electron signal. Our results show that time-resolved electron cathodoluminescence spectroscopy is a powerful tool of choice for nanophotonics, within reach of a large audience.
Highlights
One of the paradigms in nanophotonics is the engineering of the spontaneous emission decay rate of emitters
We show cathodoluminescence-based time-resolved electron beam spectroscopy in order to directly probe the spontaneous emission decay rate that is modified by the local density of states in a nanoscale environment
Our results show that time-resolved electron cathodoluminescence spectroscopy is a powerful tool of choice for nanophotonics, within reach of a large audience
Summary
One of the paradigms in nanophotonics is the engineering of the spontaneous emission decay rate of emitters. The spontaneous emission decay rate depends strongly on the local nanoscale environment via the optical local density of states (LDOS) [1], which effectively describes the coupling of light and matter. CL has gained interest in the field of nanophotonics, where the connection between the LDOS and the intensity of coherent transition radiation, induced by the electron beam [20], has been used to infer the LDOS in various metal and silicon structures far below the optical diffraction limit [21,22,23,24]. We demonstrate that deep-subnanosecond beam blanking in conjunction with time-resolved CL photon detection can be implemented using standard SEM hardware and electronics, while simultaneously reaching a λ/10 spatial resolution. By sweeping the electron beam across the aperture, pulses of electrons are generated and subsequently focused onto the sample (see Fig. 2(a))
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