Scanning Tunneling Microscopy and Spectroscopy of Rare Earth-Monopnictide Nanostructures Embedded in a Semiconducting Matrix

The atomic and electronic structure of molecular beam epitaxy (MBE)-grown rare earth-monopnictide nanostructures embedded within a III-V semiconductor matrix are examined via scanning tunneling microscopy (STM) and spectroscopy (STS). We examine several systems, including ErSb nanoparticles embedded in GaSb, ScAs nanoparticles embedded in GaAs, and ErAs nanoparticles and nanorods embedded in GaAs. Tunneling current I(V) and differential conductance dI/dV spectra show that for both ErAs nanoparticles and nanorods the local density of states (LDOS) exhibits a sharp but finite minimum at the Fermi level, demonstrating that both the particles and rods are semimetallic and not semiconducting. This observation lies in contrast to previous models of quantum confinement in ErAs. We also use STS to measure the LDOS across the ErAs/GaAs interface and discuss the formation of interface states and band bending at the interface. Finally, we discuss possible changes in the LDOS with varying nanoparticle size and varying levels of doping in the semiconductor matrix.