SURFACE MODIFICATION MECHANISM OF MATERIALS WITH SCANNING TUNNELING MICROSCOPE

The surface modification mechanism with scanning tunneling microscope (STM) is investigated. Experiments in both ultrahigh vacuum and air are reported, using several kinds of materials to understand the mechanism systematically. Threshold voltages (Vt's), which are defined as the voltages above which modification is possible under the STM tip, have linear dependence on the binding energies of the materials. Thus, the STM surface modification mechanism is attributed to the local sublimation induced by tunneling electrons. For the modification in air, it is also ascribed to the chemical reaction induced by tunneling electrons with adsorbed water, and the Vt's also fit on this line by taking the reaction energy into consideration. Therefore, the process is a direct consequence of the high flux of low-energy electrons incident on the surface from the STM tip. © 1995 American Institute of Physics.