ELECTRON MOMENTUM SPECTROSCOPY OF SINGLE CRYSTAL SILICON AND NICKEL TARGETS

M. Vos, C. Bowles, C. Chen, A.S. Kheifets, V.A. Sashin and E. Weigold

Research School of Physical Sciences and Engineering, Australian National University, Canberra 0200 ACT, Australia (maarten.vos@anu.edu.au)

In Electron Momentum Spectroscopy (EMS) an incoming electron ionizes a target and the scattered and ejected electrons are measured in coincidence. By comparing the energies and momenta of both outgoing electrons with that of the incoming electron, we can determine the energy and momentum transferred to the target, i.e. we measure the energy-resolved momentum densities including lifetime broadening and other correlation effects.. Here we present data for single crystal silicon and nickel along high-symmetry directions. Clear anisotropies in the electronic structure were found for both materials. For an infinitely thin crystal one can determine directly the magnitude of the contribution of different plane waves to the Bloch function at a given binding energy . However, for a crystal of finite thickness diffraction may occur for the incoming and/or outgoing electron beams and this complicates the interpretation. By varying measurement geometry one can vary the diffraction conditions, and hence extract valuable information on the contribution of different plane waves to the Bloch function.

Fig. 1 Measured spectral momentum density of Si along <110> and <100> directions. The dotted line is the calculated band structure. The top half shows the high momentum part on an expanded grey scale. The anisotropy is clearly resolved, and the influence of diffraction is evident as well.