Atomic force microscope tip-surface behavior under continuous bias or pulsed voltages in noncontact mode

The atomic force microscope is now widely used to oxidize a silicon surface with a continuous bias or pulsed voltages applied between the tip and the silicon surface. The aim of this letter is to study the induced electrostat ic effect on the cantilever oscillation in noncontact mode when pulsed volt ages are used for nanooxidation. Depending on the relative amplitudes betwe en electrostatic and mechanical excitations, and also on the phase between the pulsed voltages and the mechanical excitation, the cantilever response can dramatically vary. We focus on the details of controlling the feedback loop and exposure conditions in noncontact mode. (C) 2000 American Institut e of Physics. [S0003-6951(00)01308-5].