Diffusion-Dominated Luminescence Dynamics of CsPbBr3 Studied Using Cathodoluminescence and Microphotoluminescence Spectroscopy.

Time-resolved or time-correlation measurements using cathodoluminescence (CL) reveal the electronic and optical properties of semiconductors, such as their carrier lifetimes, at the nanoscale. However, halide perovskites, which are promising optoelectronic materials, exhibit significantly different decay dynamics in their CL and photoluminescence (PL). We conducted time-correlation CL measurements of CsPbBr3 using Hanbury Brown-Twiss interferometry and compared them with time-resolved PL. The measured CL decay time was on the order of subnanoseconds and was faster than PL decay at an excited carrier density of 2.1 × 1018 cm-3. Our experiment and analytical model revealed the CL dynamics induced by individual electron incidences, which are characterized by highly localized carrier generation followed by a rapid decrease in carrier density due to diffusion. This carrier diffusion can play a dominant role in the CL decay time for undoped semiconductors, in general, when the diffusion dynamics are faster than the carrier recombination.

Highly sensitive pressure and temperature induced SPP resonance shift at gold nanohole arrays.

Short range ordered (SRO) plasmonic nanohole arrays have a distinct surface plasmon polariton resonance in the visible region and exhibit an excellent sensing capability toward changes in the surrounding refractive index. While SRO and perfectly ordered plasmonic hole arrays have similar sensing properties, SRO arrays have clear advantages in fabrication, simplicity, and scalability. In this study, we use SRO gold nanoholes, which are subjected to pressure and temperature cycles, for vacuum and temperature sensing. The response of the transmission spectra to pressure changes in the range 10-3-105 Pa and temperature scans in the range 20-400 °C was recorded. Upon pressure cycling, a reversible response was observed. Upon initial temperature annealing, an irreversible blue shift in the resonance dip position was observed. Upon further temperature cycling, the resonance dip position shifts reversibly, with a notable red shift upon temperature increase. The results are discussed and interpreted based on possible molecular adsorption/desorption upon pressure cycling and in terms of the gold film's recrystallization, thermal expansion, and free electron density variations.

Momentum-resolved EELS and CL study on 1D-plasmonic crystal prepared by FIB method.

We investigate a one-dimensional plasmonic crystal (1D PlC) using momentum-resolved electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) techniques, which are complementary in terms of available optical information. The PlC sample is fabricated from large aluminum grains through the focused ion beam (FIB) method. This approach allows curving nanostructures with high crystallinity, providing platforms for detailed analysis of plasmonic nanostructures using both EELS and CL. The momentum-resolved EELS visualizes dispersion curves outside the light cone, confirming the existence of the surface plasmon polaritons (SPP) and local modes, while the momentum-resolved CL mapping analysis identified these SPP and local modes. Such synergetic approach of two electron-beam techniques offers full insights into both radiative and non-radiative optical properties in plasmonic or photonic structures.