Soft x-ray imaging and spectroscopy of single nanocrystals

Resonant photoemission electron microscopy (PEEM) at the Fe ${\mathrm{L}}_{\text{3,2}}$ absorption edge was utilized to image single $\mathrm{\gamma -}{\mathrm{Fe}}_2{\mathrm{O}}_3$ nanocrystals of 10 nm average diameter (∼20 000 Fe atoms) and to record soft x-ray absorption spectra of individual particles. Within the spectral resolution of the experiment, no damage to the individual nanoparticles occurs during repeated, prolonged exposure to the intense x-ray beam. Furthermore, no differences in the position or shape of the soft x-ray absorption spectrum of a single nanocrystal and the ensemble are observed within the experimental resolution. PEEM contrast images and soft x-ray absorption spectra, however, show strong intensity variations between different particles reflecting the size distribution of the sample. This proof-of-principle experiment successfully demonstrates the applicability of x-ray spectromicroscopy to the study of nanoscale systems on a hitherto unachieved length scale.