TUNNELING POTENTIAL BARRIER DEPENDENCE OF ELECTRON-SPIN POLARIZATION

Scanning tunneling microscopy experiments reveal that the degree of spin polarization of electrons tunneling from Ni into a semiconductor increases with decreasing potential barrier thickness. The results show that the highly polarized 3d bands as well as the low-polarized 4sp bands contribute to the tunneling current and that the ratio of their tunneling probabilities depends on the potential barrier thickness and height. Furthermore, the tunneling potential barrier for the 3d-like levels is estimated to be similar to 1 eV higher than for the 4sp contribution.