Photoemission electron microscopy (PEEM) with Time-of-flight detection enables the aquisition of electron images with time resolution in the 150 ps range.
That means for every electron hitting the detector not only the X and Y coordinates are recorded, but also the arrival time. This allows to acquire images within a fixed time intervall. Furthermore, by conversion of the time-scale into an energy-scale, the local band structure can be recorded.
The TOF PEEM is especially useful with a pulsed excitation source, such as a synchrotron or a pulsed laser. The TOF detector is based on a Delay Line Detector (DLD) by Surface Concept GmbH, a Spin-off of the University of Mainz [1,2].
Test data have been measured with a blue diode laser (3.1 eV), with repetition rates of 10 MHZ and 20 MHZ.
The test sample was an Ag layer on a microstructured Si substrate. Electron emission is dominated by the 2 PPE process. The huge intensity difference between "hot spots" and background areas demonstrate the good dynamic range of the DLD. |
