Microspectroscopy and imaging using a delay line detector in time-of-flight photoemission microscopy

A method for microspectroscopy and energy-selective imaging using a special photoemission electron microscope (PEEM) is presented. A modified commercial PEEM was combined with a delay line device as x, y, t detector serving as the basic arrangement for spectromicroscopy. One can measure the time of flight of the electrons passing a drift section in order to analyze the energy distribution of photoelectrons in PEEM. The time of flight is referenced to the time structure of the synchrotron radiation from an electron storage ring. At electron kinetic energies of less than 20 eV within the drift region a spatial resolution of about 100 nm has been obtained. Fast counting electronics (instead of a camera) delivers an image for real-time monitoring on an oscilloscope screen or for image acquisition by a computer. A time resolution of about 500 ps has been obtained with the potential of further improvement. The spatial resolution of the delay line detector is about 50 mum in the image plane corresponding to 1000 pixels in the image diagonal. Direct photoemission from the W-4f core level of a W(110) single-crystal sample was observed at several photon energies. The W-4f fine-structure splitting of 2.3 eV could be well resolved at a pass energy around 40 eV through the drift region. (C) 2001 American Institute of Physics.