MICROSCOPY Vol.46▶No.1 2011
■Researches Today

Detection of Single Electron Spin by Using Scanning Tunneling Microscope (STM)

Tadahiro Komeda

Abstract: We discuss the detection of a single spin by monitoring the tunneling current of the scanning tunneling microscope (STM). First example is the detection of a single spin by the observation of the Kondo resonance feature, which is formed by a single spin placed in the conductance electrons and appeared as a sharp feature at the Fermi level in the differential conductance plot. When investigated on a double-decker bis(phthalocyaninato)terbium(III) complex (TbPc2) adsorbed on an Au(111) surface, the dI/dV curve of the tunneling current recorded onto a TbPc2 molecule shows a Kondo peak whose origin is an unpaired spin of a π-orbital of a Pc ligand. Next the detection of a single spin by monitoring the high-frequency component of the tunneling current in the presence of a magnetic field. For a submonolayer oxide thin film on the Si(111)-7×7 surface, it was demonstrated that a spin signal synchronized with the Larmor precession of the electron spin associated with a dangling bond can be detected. With site-specific measurement, it was found that the spin signal appears on the bright Si adatom in which oxygen atoms occupy the backbonds and weakened the metallic nature of the Si(111)- 7×7 surface. The measured Larmor frequency corresponded to g~2.00.

Key words: scanning tunneling microscope, spin, tunneling spectroscopy, ESR-STM, Kondo resonance