Scanning probe energy loss spectroscopy: Angular resolved measurements on silicon and graphite surfaces

We report angle resolved “scanning probe energy loss spectroscopy” measurements from Si(111)-7×7 and graphite surfaces. Electrons incident on the surface after field emission from a scanning tunneling microscope tip are backscattered and detected with an energy and angle resolved hemispherical analyzer. We find that the reflected signal is sharply peaked in the direction parallel to the surface plane. Characteristic energy loss peaks corresponding to bulk and surface plasmon modes of the different surfaces are observed.