Scanning probe energy loss spectroscopy below 50nm resolution

Abstract

We report scanning probe energy loss spectroscopy (SPELS) measurements from a roughened Si(111) surface in ultrahigh vacuum. The experiments, which utilize a scanning tunneling microscope tip in the field emission mode as the electron source, establish that the spatial resolution in SPELS is better than 50nm. The spectral maps acquired indicate different contrast mechanisms for the inelastically scattered and secondary electrons identified in the energy loss spectrum.

Surface plasmon excitation of Au and Ag in scanning probe energy loss spectroscopy

“…[1][2][3][4][5] In addition to surface plasmons, interband transitions, and similar electronic excitations, local secondary electron energy spectra are also measured. We show that the spectra obtained in SPELS depend strongly on the incident electron beam energy.…”

Thirty per cent contrast in secondary-electron imaging by scanning field-emission microscopy

“…One important added value of the SFM imaging mode is that electrons can escape the junction, so that they can be made available to further analysis, e.g. energy [10,11,20] and/or spin resolved spectroscopy [7,9] 5 or for further processing. The astonishing high number of electrons actually escaping the junction 6 speak also for the feasibility of imaging with sub-picosecond temporal resolution.…”

Mapping the plasmon response of Ag nanoislands on graphite at 100 nm resolution with scanning probe energy loss spectroscopy

“…In the spectrometer, the electrons are energy-dispersed in a 127°c ylindrical sector analyzer onto a multichannel analyzer (MCA). This detector allows for faster sampling of the energy loss spectrum of the backscattered electrons compared with the SPELS instrument used in previous studies, 5,8,10) which utilized a concentric hemispherical analyzer (CHA) and channeltron. In order to minimize the stray electric fields around the STM junction, the microscope has been modified by incorporating additional electrostatic shielding around the STM tip and the piezo scanner.…”

“…Most previous studies have reported single-point or area-averaged measurements, and there have only been a few studies where spatially resolved maps of energy loss features have been reported. 8,9) Using a retarding field analyzer, Festy and Palmer 8) spectroscopically imaged the surface features on roughened silicon with a sub-50-nm spatial resolution, indicating that it should be possible to provide chemical analysis at these length scales. More recently, Xu et al 9) used a toroidal detector to map the plasmon loss features of Ag islands on graphite, clearly demonstrating that the Ag islands could be chemically distinguished from the graphite support, but with a limited spatial resolution of 5 µm.…”