PHOTOELECTRON HOLOGRAPHY FOR HIGH-RESOLUTION SPECTROMICROSCOPY

X-ray photoelectron spectromicroscopy seeks to couple high spatial resolution with a contrast mechanism derived from the photoelectron binding-energy chemical shift. The two major approaches to direct surface imaging with photoelectrons are based either on using a focused incident X-ray beam which is scanned over the sample, or on electron optical techniques which form a magnified image of the surface using the emitted electrons. Due to practical problems and optical aberrations, both approaches appear to have an ultimate spatial resolution limit in the range of 10 nm. An alternative approach to mapping the locations of atoms in specific chemical states is X-ray photoelectron holography, which has the possibility for producing maps of the positions of photoemitting atoms with atomic resolution. Advantages and limitations of this new technique for emission spectromicroscopy are discussed.