Effect of the tip-sample contact force on the nanostructure size fabricated by local oxidation nanolithography

Nanofabrication technique based on atomic force microscope (AFM)/scanning tunneling microscope (STM) can be applied to the fabrication of semiconductor micro/nano devices. Here, many oxide wires on Si surface were fabricated using conductive contact mode and tapping mode AFM in ambient atmosphere. The experiments show that tip-sample contact force plays an important role in electric-field-induced anodization with AFM. It is proved that the height and aspect ratio of oxide structures fabricated by contact mode AFM nano-oxidation technique will decrease gradually with increasing contact force between the tip and the sample. Compared with oxide structures fabricated by contact mode AFM, nanofabrication based on tapping mode AFM gives higher aspect ratio and height of oxide structures and narrower oxide width because of decreased contact force. In addition, field-induced oxidation by tapping mode AFM gives higher flexibility on the control of oxide size and aspect ratio by varying the oscillation amplitude, the range of the damping ratio with about 10%∼38% can optimize the height and aspect ratio of oxide structures.

► The tip-sample contact force plays an important role in field-induced anodization.
► Aspect ratio of structures fabricated by contact mode AFM decreases with increasing force.
► The range of the typical force with 0 nN∼150 nN would optimize the oxide structures.
► Field-induced oxidation based on tapping mode AFM gives higher flexibility.
► The range of damping ratio with 10%∼38% can optimize the aspect ratio of structures.