  The atomic and electronic structures of ErAs nanoparticles embedded within a
GaAs matrix are examined via cross-sectional scanning tunneling microscopy and
spectroscopy (XSTM/XSTS). The local density of states (LDOS) exhibits a finite
minimum at the Fermi level demonstrating that the nanoparticles remain
semimetallic despite the predictions of previous models of quantum confinement
in ErAs. We also use XSTS to measure changes in the LDOS across the ErAs/GaAs
interface and propose that the interface atomic structure results in electronic
states that prevent the opening of a band gap.
