Field evaporation of gold atoms onto a silicon dioxide film by using an atomic force microscope

Abstract

To investigate whether field evaporation of gold atoms is responsible for dot formation in an atomic force microscope (AFM) gold-coated tip/vacuum/SiO2 film/p-type Si substrate configuration, we have performed elemental analysis of the dots and measured the dependence of the threshold voltage on SiO2 thickness with both polarities for the dot formation. The experiments demonstrate that it is feasible to form gold dots on SiO2 films 17–107 Å thick by adjusting the pulsed voltages applied to the gold-coated AFM tip. Energy dispersive x-ray spectroscopy (EDX) shows that the dots include gold. The threshold voltages increase almost linearly with the SiO2 thickness. Furthermore, the voltage with negative polarity is lower than that with positive polarity. These results provide evidence that the dot formation on the SiO2 film using AFM occurs by field evaporation.