Effects of Beam-Induced Carbon Deposition on Electron Energy-Loss Spectroscopy Analysis of Compositional Fluctuations in InGaN/GaN Quantum Well LEDs

Electron energy-loss spectroscopy (EELS) performed in an aberration-corrected STEM has a higher signal-to-noise ratio compared to EELS in a conventional STEM, allowing for more information to be extracted from the ionization edges. Additionally, the higher resolution in aberration-corrected STEM translates to higher resolution EELS maps. However, the higher current densities in aberration-corrected STEM increase the possibility of developing beam-induced artifacts, and the ability to collect angstromlevel EELS maps further increases the sample exposure. One such effect that can become exacerbated from high exposure is beam-induced deposition of carbon-rich condensates, which arises from interaction of electrons with hydrocarbons in the sample vicinity The presence of carbon deposition is indicated by the appearance of the C K-edge at 284 eV in the EELS spectrum (Figure For many materials systems, the C K-edge can be disregarded because it does not overlap with other ionization edges of interest. However, in the case of indium or nitrogen, the C K-edge is close in energy to the N K-edge at 400 eV and the In M-edge at 480 eV (Figure