Dependence of electric field on STM tip preparation

Voltage pulses applied between an STM tip and a surface can modify the surface on the nanometer scale due to electric-field-induced evaporation. However, at present, different groups have achieved surface modification with quite different bias conditions, and it is still difficult to obtain high reproducibility in such experiments. In this paper, we measure the tip displacement during a pulse at constant tunnelling current, and deduce that the electric field produced by the pulse depends in a systematic way on tip preparation. The results show how differences in tip preparation can be a major source of irreproducibility for STM nanofabrication and atom manipulation. q1998 Elsevier Science B.V. All rights reserved