Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy

Jean-Christophe Le Breton (1) , Sylvain Tricot (1) , Gabriel Delhaye (1) , B. Lépine (1) , Pascal Turban (1) , Philippe Schieffer (1)

1 IPR - Institut de Physique de Rennes

The control of tunnel contact resistance is of primary importance for semiconductor-based spintronic devices. This control is hardly achieved with conventional oxide-based tunnel barriers due to deposition-induced interface states. Manipulation of single 2D atomic crystals (such as graphene sheets) weakly interacting with their substrate might represent an alternative and efficient way to design new heterostructures for a variety of different purposes including spin injection into semiconductors. In the present paper, we study by x-ray photoemission spectroscopy the band alignments and interface chemistry of iron-graphene-hydrogenated passivated silicon (001) surfaces for a low and a high n-doping concentration. We find that the hydrogen passivation of the Si(001) surface remains efficient even with a graphene sheet on the Si(001) surface. For both doping concentrations, the semiconductor is close to flat-band conditions which indicates that the Fermi level is unpinned on the semiconductor side of the Graphene/Si(001):H interface. When iron is deposited on the graphene/Si(001):H structures, the Schottky barrier height remains mainly unaffected by the metallic overlayer with a very low barrier height for electrons, a sought-after property in semiconductor based spintronic devices. Finally, we demonstrate that the graphene layer intercalated between the metal and semiconductor also serves as a protection against iron-silicide formation even at elevated temperatures preventing from the formation of a Si-based magnetic dead layer. © 2016 Author(s).

Keywords: Doping concentration; Substrates; Silicon; Elevated temperature; Hydrogen passivation; Heterojunctions; Interface states; Iron; Magnetoelectronics; Passivation; Photoelectron spectroscopy; Schottky barrier diodes; Semiconducting silicon; Semiconductor devices; Semiconductor doping; Silicides; Interface chemistry; Magnetic dead layers; Schottky barrier heights; Spintronic device; X ray photoemission spectroscopy; Graphene

Domains: Physics [physics]

Jean-Christophe Le Breton, Sylvain Tricot, Gabriel Delhaye, B. Lépine, Pascal Turban, et al.. Band alignments in Fe/graphene/Si(001) junctions studied by x-ray photoemission spectroscopy. Applied Physics Letters, 2016, 109 (5), pp.051601. ⟨10.1063/1.4960199⟩. ⟨hal-01372806⟩