Study on time resolution of single event TOF-RBS measurement

Flight paths and times of secondary electrons, induced by a focused ion beam, from a sample to a secondary electron detector (SED), were simulated with various shield shapes of a SED for improving the time resolution of time-of-flight Rutherford backscattering spectrometry (TOF-RBS) using the secondary electron signal as a start signal, the results of which were compared with experimental time resolutions of the TOF-RBS measurement. The fluctuation in the flight path and, hence, flight time of the secondary electron deteriorates the time resolution of TOF-RBS. The simulated flight time differences for SEDs with or without a shield were 4.4–41 ns with a shield and 1.0 ns without a shield, respectively, indicating that the SED without the shield would improve the time resolution of the single event TOF-RBS. The time resolutions of TOF-RBS using 150 keV Be+ for Au/Si sample with SEDs with and without a shield were 5.6–9.2 and 4.4 ns, respectively. The improved time resolution for SEDs without the shield was confirmed experimentally.