Bias-induced transfer of an aluminum atom in the scanning tunneling microscope

The transfer of an Al atom between tip and sample in the scanning tunneling microscope is analyzed theoretically. The bias required to reduce the activation barrier for transfer to zero is a strong function of tip-sample separation, changing from ∼5 to ∼0.5 V over a separation range of 2. The degree of bias-induced ionization of the atom is found to be small for the range of separations studied. © 1994 The American Physical Society.