Analysis of electric field-induced fabrication on Au and Ti with an STM in air

Studies of the modification mechanism of Au and Ti surfaces by electric fields applied with a scanning tunneling microscope (STM) are carried out at atmospheric pressure and room temperature. For pulses of 1–100 μs, nanodots can only be formed on Ti under conditions where the current shows substantial fluctuations, indicating tip–sample contact. If the field is applied gradually, Au is not affected and pits are formed on Ti. We interpret pit formation as a result of field-induced oxidation. Moreover, experiments show that the relative humidity plays an important part in nanostructure formation on Ti. Our results can be explained through a combination of direct contact and oxidation induced by electric field.