Imaging Strain-Localized Single-Photon Emitters in Layered GaSe below the Diffraction Limit.

Nanoscale strain control of exciton funneling is an increasingly critical tool for the scalable production of single photon emitters (SPEs) in two-dimensional materials. However, conventional far-field optical microscopies remain constrained in spatial resolution by the diffraction limit and thus can provide only a limited description of nanoscale strain localization of SPEs. Here, we quantify the effects of nanoscale heterogeneous strain on the energy and brightness of GaSe SPEs on nanopillars with correlative cathodoluminescence, photoluminescence, and atomic force microscopy, supported by density functional theory simulations. We report the strain-localized SPEs have a broad range of emission wavelengths from 620 to 900 nm. We reveal substantial strain-controlled SPE wavelength tunability over a ∼100 nm spectral range and 2 orders of magnitude enhancement in the SPE brightness at the pillar center due to Type-I exciton funneling. In addition, we show that radiative biexciton cascade processes contribute to observed CL photon superbunching. Also, the GaSe SPEs show excellent stability, where their properties remain unchanged after electron beam exposure. We anticipate that this comprehensive study on the nanoscale strain control of two-dimensional SPEs will provide key insights to guide the development of truly deterministic quantum photonics.

The extent and time-course of mountain blanket peat erosion in Ireland.

Erosion of upland blanket pent is widespread in Britain and Ireland and suggestions for its initial causes have included recent human disturbance and changes in the mechanical stability of the peat masses through time. A survey of blanket peat in five mountain areas in Ireland revealed extensive erosion in all areas, and two cores of mountain lake sediment contained inwashed peat in their upper sections. Detailed analysis of the core from the Wicklow Mountains revealed pollen evidence for initial peatland development, tree clearance and eventual peat erosion. The inwashed peat contained abundant Sphagnum leaves. Peat inwash began 1500 years ago in Donegal, N.W. Ireland and 3000 years ago in Wicklow near the east coast. The occurrence of erosion over these time periods does not suggest that recent human activity and changes in land-use are the original causes of erosion. Recent human activity has merely intensified erosion that probably originated from peat flows or the development of natural drains in mature peat masses developing on sloping ground.