Surface resonance of the (2 × 1) reconstructed lanthanum hexaboride (001)-cleavage plane: A combined STM and DFT study

摘要

We performed a combined study of the (001)-cleavage plane of lanthanum hexaboride (LaB6) using scanning tunneling microscopy and density-functional theory (DFT). Experimentally, we found a (2 x 1) reconstructed surface on a local scale. The reconstruction is only short-range ordered and tends to order perpendicularly to step edges. At larger distances from surface steps, the reconstruction evolves to a labyrinthlike pattern. These findings are supported by low-energy electron diffraction experiments. Slab calculations within the framework of DFT show that the atomic structure consists of parallel lanthanum chains on top of boron octahedra. Scanning tunneling spectroscopy shows a prominent spectral feature at -0.6 eV. Using DFT, we identify this structure as a surface resonance of the (2 x 1) reconstructed LaB6 (100) surface which is dominated by boron dangling bond states and lanthanum d states.