Core level photoelectron spectromicroscopy with Al Kα1 excitation at 500 nm spatial resolution

Core level photoelectron spectromicroscopy in laboratory conditions (XPS imaging) with standard Al Kα1 excitation (1486.6 eV), either in scanning or parallel imaging mode, is currently limited to a spatial resolution of ∼4 μm. Using energy-filtered X-ray photoelectron emission microscopy (XPEEM) and a bright monochromated Al Kα source (photon flux ∼1012 photons/(s mm2)), we demonstrate refined results regarding lateral and energy resolutions on cross-sectioned epitaxial Si/SiGe layers imaged with photoelectrons of 266.4 eV energy referred to the Fermi level of the sample (Ge 2p3/2 transition). Despite an elemental contrast of only 50%, XPS imaging performed this way has an edge lateral resolution of 480 nm and an energy resolution of 0.56 eV, the spectroscopic information being available at the decanometric scale. Since the lateral resolution is only limited by the counting statistics due to a modest illumination flux, this method paves the way to laterally resolved XPS and UPS in the 100 nm range.