In recent years the combination of magnetic materials with well known semiconductors
has grown in interest due to their potential use in the new field
of spin electronics. The transition metals Fe, Co, Ni, and Cr and their silicide
formation have been studied in detail while little has been done on the thin film
formation of manganese silicides. Here we report the first angle resolved photoelectron
spectroscopy (ARPES) study of the √3×√3 phase of thin annealed
manganese films on Si(111). This is combined with low energy electron diffraction
(LEED), scanning tunneling microscopy (STM) and scanning tunneling
spectroscopy (STS) studies.
Evaporating a few monolayers (ML) of manganese onto the Si(111)-7×7
surface followed by post annealing at 400 °C for 5 min resulted in a sharp √3×√3 phase. The valence band spectra of the √3×√3 surface show a clear
metallic character due to the sharp Fermi edge, which is consistent with earlier
results [1-2]. In the angle resolved photoemission spectra at low temperature
(LT, 100 K) along the Γ-M-Γ
line of the √3×√3 surface Brillouin zone, at least three
surface states are observed. Also in the
Γ-K-M direction, at least three surface states are observed. STM measurements of the √3×√3 surface show an almost fully covered surface. The STM images show
a very nice, ordered √3×√3 arrangement. On top of the √3×√3 surface,
adatoms with a threefold coordination, having a concentration of ~15%, are
clearly seen. STS measurements on this surface show a high density of states
around the Fermi level indicating that the surface is metallic.
[1] A. Kumar, M. Tallarida, M. Hansmann, U. Starke, K. Horn, J. Phys. D:
Appl. Phys. 37 (2004) 1083-1090
[2] E. Magnano, E. Carleschi, A. Nicolaou, T. Pardini, M. Zangrando, F.
Parmigiani, Surf. Sci. 600 (2006) 3932-3937
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