Eu-Si nanowires formation on Si(100) studied by scanning tunneling microscopy and spectroscopy

By depositing Eu onto a cleaned Si(100) surface at 400 ^oC, patterned nanowires are formed and visualized by scanning tunneling microscopy(STM). The nanowires are measured to be ~1.5 nm in diameter, ~1 Å in height and hundreds of nm or more in length. The spacing between the nanowires are found to be mostly 2.2 nm, 2.8 nm and 3.4nm, i.e. with 0.6 nm increment. Interestingly, the topography images taken at positive and negative bias show single-wire and double-wire morphologies, respectively. Same observations are made in the dI/dV mapping with positive and negative bias. Furthermore, dI/dV spectra taken at the double-wire features (found while scanning at negative bias) exhibit peak-valley features in the valence band - a peak at -3.2 V and valley at -3.4 V. Similar peak-valley dI/dV spectra were reported for the Pt/Si nanowires, which showed signs of strong Rashba spin splitting [1]. Further studies are underway in determining the possibility of strong Rashba effect in this Eu/Si nanowire systems.

[1] J. Park, S. W. Jung, M. C. Jung, H. Yamane, N. Kosugi, and H. W. Yeom, Phys. Rev. Lett. 110, 036801 (2013).