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

Abstract

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 μm 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.

Incoherent magnetization rotation observed in subnanosecond time-resolving x-ray photoemission electron microscopy

“…Prior to the field pulse, both elements reveal Landau-like (flux-closure dominated) domain patterns. 11,12 This important finding proves the sample to reproducibly relax back into the same state after each field pulse cycle. Obviously, the demagnetizing field takes the role of the static bias field applied a)…”

“…10 The instrument features a dual image detection system: a standard imaging unit (phosphor screen and 12-bit slow scan CCD camera) and a two-dimensional delay-line detector 11 for low-signal applications. This delay-line detector was particularly employed in previous experiments using low-flux single-bunch operational mode.…”

The formation of NO+ from the reaction of N22+ with O2

“…The PSD is a commercial device in which the electron pulse from a pair of multichannel plates ͑MCP͒ impacts on two, perpendicularly wound, wire anodes of known lengths. 100,101 The position of the ion arrival in the plane of the detector ͑x , y͒ can then be derived from the time of arrival of the charge pulse at the end of each anode wire. The charge pulse from the MCP propagates along each wire to its ends and the signals from both ends of the two wires are passed as stop pulses to the timing circuitry, resulting in four times ͓t xa ͑i͒ , t xb ͑i͒ , t ya ͑i͒ , t xb ͑i͔͒ for each ion in the pair ͑i =1,2͒.…”

Nanoscale Imaging and Spectroscopy with XPEEM

“…Obviously, this kind of PEEM requires a detector with high temporal resolution , which is the main technical difficulty in this approach. With a delay line detector, a time resolution of 0.5 ns has been achieved, 24) which corresponds to a theoretical energy resolution of 60 meV at 10 eV and of 2 eV at 100 eV. In first test experiments, an energy resolution of 400 meV at 43 eV has been achieved, while a lateral resolution of less than 100 nm has been reported.…”

“…In first test experiments, an energy resolution of 400 meV at 43 eV has been achieved, while a lateral resolution of less than 100 nm has been reported. 24) In the future, PEEM systems with TOF analyzer might become very useful in combination with XFEL sources.…”