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

A method of imaging a sample with a probe-based AFM having a self-actuated cantilever and a Z-position actuator, the method comprising the steps of:

• scanning, with the self-actuated cantilever, a surface of the sample at a predetermined scanning rate;
• 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 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 in response to said cantilever control signal wherein said first feedback circuit is 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.

An AFM for analyzing a surface of a sample in cyclical mode, the AFM comprising:

• a self-actuated cantilever having a Z-positioning element integrated therewith;
• an oscillator that oscillates said self-actuated cantilever;
• a first feedback circuit that generates a cantilever control signal in response to vertical displacement of said self-actuated cantilever during a scanning operation;
• a second feedback circuit responsive to said cantilever control signal to generate a position control signal, wherein said first feedback circuit is nested within said second feedback circuit;
• and
• a Z-position actuator, responsive to said position control signal, to position one of said self-actuated cantilever and the sample to change the spacing between the self-actuated cantilever and the sample;
• wherein said self-actuated cantilever is responsive to said cantilever control signal to keep a parameter of probe oscillation generally constant.

An AFM comprising:

• a first feedback loop that outputs a first feedback signal;
• a self-actuated cantilever controlled by said first feedback signal;
• and
• a Z-position actuator controlled by a second feedback loop, wherein said first feedback loop is nested within said second feedback loop so as to permit said second feedback loop to use said first feedback signal as an error signal.

A method of imaging a sample in cyclical mode with a probe-based AFM having a self-actuated cantilever and a Z-position actuator, the method comprising the steps of:

• scanning a surface of the sample with the self-actuated cantilever, the self-actuated cantilever including a Z-positioning element integrated therewith;
• generating a deflection signal in response to a deflection of the self-actuated cantilever during said scanning step;
• applying an oscillating driving voltage to said Z-positioning element to oscillate the self-actuated cantilever;
• generating a cantilever control signal in response to said deflection signal;
• maintaining a parameter associated with the oscillation of the self-actuated cantilever at a constant value by servoing the position of the self-actuated cantilever relative to the sample in response to said cantilever control signal;
• generating a position control signal in response to said cantilever control signal;
• and
• controlling the Z-position actuator in response to said position control signal.

A method of imaging a sample in cyclical mode with a probe-based AFM, the method comprising the steps of:

• providing a self-actuated cantilever and a piezo-tube Z-position actuator, said self-actuated cantilever including a Z-positioning element integrated therewith;
• oscillating, with said Z-positioning element, said self-actuated cantilever at a cantilever resonant frequency and at a predetermined amplitude of oscillation;
• scanning a surface of the sample with said self-actuated cantilever;
• generating a deflection signal in response to said scanning step;
• generating, with a first feedback loop, a cantilever control signal in response to said deflection signal;
• maintaining said amplitude of oscillation at a constant value in response to said cantilever control signal;
• and
• using said cantilever control signal as an error signal in a second feedback loop to control the Z-position actuator, wherein said first feedback loop is nested within said second feedback loop.

A method of analyzing a surface of a sample with a probe based AFM, the method comprising the steps of:

• providing a self-actuated cantilever having (1) an elongated member comprised of silicon and (2) a Z-positioning element comprised of zinc oxide;
• oscillating said self-actuated cantilever at a cantilever resonant frequency and at a predetermined amplitude of oscillation;
• scanning the surface with said self-actuated cantilever;
• generating a deflection signal in response to said scanning step;
• generating, with a first feedback loop, a cantilever control signal in response to said deflection signal;
• maintaining said amplitude of oscillation at a generally constant value in response to said cantilever control signal;
• using said cantilever control signal as an error signal in a second feedback loop to generate a position control signal, wherein said first feedback loop is nested within said second feedback loop;
• and
• heating said self-actuated cantilever in response to said position control signal to control the Z-position of said self-actuated cantilever.

A method of analyzing a sample in cyclical mode with a probe-based AFM having a self-actuated cantilever and a Z-position actuator, the self-actuated cantilever including a Z-positioning element integrated therewith, the method comprising the steps of:

• applying an oscillating driving voltage to said Z-positioning element to oscillate the self-actuated cantilever and to cause a tip of the cantilever to intermittently contact a surface of the sample;
• generating a deflection signal in response to a deflection of the self-actuated cantilever;
• generating a cantilever control signal in response to said deflection signal;
• maintaining a parameter associated with the oscillating of the self-actuated cantilever at a constant value by servoing the position of the self-actuated cantilever relative to the sample in response to said cantilever control signal;
• generating a position control signal in response to said cantilever control signal;
• and
• controlling the Z-position actuator in response to said cantilever control signal.

A method of analyzing a sample in cyclical mode with a probe-based AFM having a self-actuated cantilever and a Z-position actuator, the self-actuated cantilever including a Z-positioning element integrated therewith, the method comprising the steps of:

• generating a deflection signal in response to a deflection of the self-actuated cantilever during said scanning step;
• applying an oscillating driving voltage to said Z-positioning element to oscillate the self-actuated cantilever;
• generating a cantilever control signal in response to said deflection signal;
• maintaining a parameter associated with the oscillation of the self-actuated cantilever at a constant value by servoing the position of the self-actuated cantilever relative to the sample in response to said cantilever control signal;
• generating a position control signal in response to said cantilever control signal;
• and
• controlling the Z-position actuator in response to said position control signal.

An AFM for analyzing a surface of a sample, the AFM comprising:

• a cantilever;
• a first feedback circuit that generates a cantilever control signal in response to vertical displacement of said cantilever during a scanning operation;
• a second feedback circuit responsive to said cantilever control signal to generate a position control signal, wherein said first feedback circuit is nested within said second feedback circuit;
• and
• a Z-position actuator, responsive to said position control signal, to position one of said cantilever and the sample to change the spacing between the cantilever and the sample;
• wherein said self-actuated cantilever is responsive to said cantilever control signal to keep a parameter of cantilever operation generally constant;
• wherein said position control signal is indicative of a low frequency component of the topography of the surface, and said cantilever control signal is indicative of a high frequency component of the topography of the surface;
• wherein the low frequency component includes the slope of the surface topography.