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 evaporat ion. However, at present, different groups have achieved surface modif ication with quite different bias conditions, and it is still difficul t to obtain high reproducibility in such experiments. In this paper, w e measure the tip displacement during a pulse at constant tunnelling c urrent, and deduce that the electric field produced by the pulse depen ds in a systematic way on tip preparation, The results show how differ ences in tip preparation can be a major source of irreproducibility fo r STM nanofabrication and atom manipulation. (C) 1998 Elsevier Science B.V. All rights reserved.