Inelastic electron tunneling spectroscopy of local "spin accumulation" devices

TL;DR

This study uses inelastic electron tunneling spectroscopy to show that local spin signals in ferromagnet/insulator/n-Si junctions are caused by inelastic tunneling through impurities, not by spin accumulation in silicon.

Contribution

It reveals that 3T magnetoresistance signals originate from inelastic tunneling effects, challenging the previous assumption of spin accumulation as the cause.

Findings

IETS spectra depend on voltage bias and magnetic field.

Magnetoresistance signals are due to inelastic tunneling, not spin accumulation.

Impurities and defects dominate tunneling processes.

Abstract

We investigate the origin of purported "spin accumulation" signals observed in local "three-terminal" (3T) measurements of ferromagnet/insulator/n-Si tunnel junctions using inelastic electron tunneling spectroscopy (IETS). Voltage bias and magnetic field dependences of the IET spectra were found to account for the dominant contribution to 3T magnetoresistance signals, thus indicating that it arises from inelastic tunneling through impurities and defects at junction interfaces and within the barrier, rather than from spin accumulation due to pure elastic tunneling into bulk Si as has been previously assumed.