Active probe for an atomic force microscope and method for use thereof

A method of measuring a sample in a fluid cell containing a fluid with a probe-based AFM having a self-actuated cantilever and a Z position actuator, the method comprising:

• placing the sample in a fluid cell for holding the fluid, and placing the self-actuated cantilever in the fluid cell;
• scanning a surface of the sample with the self-actuated cantilever;
• detecting a deflection of the cantilever in response to said scanning step and generating a corresponding deflection signal;
• generating, with a first feedback circuit, a cantilever control signal, the cantilever control signal being generated in response to said deflection signal;
• applying said cantilever control signal to the self-actuated cantilever to maintain a generally constant force between the self-actuated cantilever and the surface during said scanning step;
• generating, with a second feedback circuit, a position control signal, the position control signal being generated in response to said cantilever control signal, and said first feedback circuit being nested within said second feedback circuit;
• and
• applying said position control signal to the Z position actuator to position the sample during said scanning step.

A method of actively changing the bandwidth of amplitude detection of an AFM, the method comprising:

• providing a self-actuated cantilever having a piezoelectric element disposed thereon;
• providing a cantilever drive circuit;
• driving the self-actuated cantilever at a cantilever resonant frequency with an oscillation voltage signal;
• scanning a surface of a sample with the self-actuated cantilever;
• during said scanning step, generating a deflection signal in response to a deflection of the self-actuated cantilever;
• and
• in response to the deflection signal, operating the cantilever drive circuit to actively modify a quality factor (Q) associated with the self-actuated cantilever.