High-Resolution Cathodoluminescence (CL) for Characterization of Nanophotonic Structures

The emergence of nanophotonic devices appeal for sub-wavelength optical characterization techniques. Various techniques such as scanning near-field optical microscopy (SNOM) or stimulated emission depletion (STED) microscopy... [ view full abstract ]

The emergence of nanophotonic devices appeal for sub-wavelength optical characterization techniques. Various techniques such as scanning near-field optical microscopy (SNOM) or stimulated emission depletion (STED) microscopy are now currently used in the field of nano-optics. Here, we introduce cathodoluminescence CL as a powerful and versatile technique for optical and structural characterization of nanoscale structures. CL can be performed in a scanning electron microscope (SEM or STEM) to study nanostructures made of semiconductors, metals or insulators. It offers several advantages over usual optical spectroscopy techniques. The multimode imaging capabilities of the SEM enable the correlation of optical properties (via CL) with surface morphology (secondary electron – SE – mode) at the nanometer scale [1].

In semiconductors and insulators, the CL signal gives local information on the electronic bandgap and defect states. In nanoresonators such as photonic crystals or metal nano-antennas, CL directly maps local density of optical states (LDOS) [2]. In addition, CL has been recently used in nano quantum optics experiments [3].

We intend to show a selection of results obtained with SEM-CL on various semiconductor and metal nanostructures, such as nanowires [4], microdisks [5] or nanoapertures in metal films [6]. These structures find applications for single photon emission, nanolasing or color generation at the nanoscale. Finally, we will show how the introduction of pulsed electron excitation and time resolved detection of the CL signal (TRCL) allows carrier dynamic probing at the nanoscale [7].

[1] L. Reimer in “Scanning Electron Microscopy”, (Springer, Berlin) Ch. 1.
[2] M. Kociak and O. Stéphan, Chem. Soc. Rev. 43 (2014), p. 3865.
[3] L.H.G. Tizei and M. Kociak, Phys. Rev. Lett. 110 (2013), p. 153604.
[4] Fontana et al, Phys. Rev. B 90 (2014), p. 075307.
[5] Puchtler et al, ACS Photonics 2 (2015), p. 137.
[6] Segal et al, Nanoscale 8 (2014), p. 15296.
[7] Shahmohammadi et al, Nano Lett. 16 (2016), p. 243.