Wave-vector imaging photoelectron spectrometer

Abstract

We have developed an imaging photoelectron spectrometer based on a simple electrostatic immersion lens with the capability of measuring photoemission intensity as a function of the parallel component of electron wave vector throughout the Brillouin zone. The image is a simple rectilinear mapping of the k∥ component of the wave vector in reciprocal space. Using a retarding field-energy selection system, it is possible to energy select and image the various states below the Fermi energy. We obtain an energy resolution of 0.3 eV and a k∥ resolution of 0.04 Å−1. The distribution of photocurrent is amplified onto a phosphor screen by a channel electron multiplier array. The image on the screen is then picked up with a charge-coupled device (CCD) camera so that the digitized image can be both position and energy analyzed. The performance of the system is demonstrated by imaging the photoelectron distribution from a Cu(001) single crystal. We find that the intensity distribution of emission in k space reflects the dispersion of the projected bulk energy band structure.