Claims
- 1. A method of actively changing the bandwidth of amplitude detection of an AFM having a cantilever, the method comprising:
applying an oscillating drive signal to the cantilever; measuring a response of the cantilever during operation; demodulating the response; and dynamically controlling the oscillating drive signal based on the demodulated response.
- 2. The method according to claim 1, wherein said dynamically controlling step includes using an amplitude detection circuit.
- 3. The method according to claim 2, wherein said demodulating step includes using an RMS-to-DC converter to determine an amplitude of the measured response and to generate a corresponding amplitude signal.
- 4. The method according to claim 3, further comprising the step of generating an error signal based on the amplitude signal, and wherein the amplitude detection circuit includes a gain stage that applies a gain to the error signal to generate a modified amplitude signal.
- 5. The method according to claim 4, wherein the gain is manually selected by a user.
- 6. The method according to claim 4, wherein said dynamically controlling step includes modulating the oscillating drive signal with the modified amplitude signal.
- 7. The method according to claim 6, further including the step of summing the modified amplitude signal with a selected amplitude offset signal.
- 8. The method according to claim 1, wherein said measuring step includes using an optical beam bounce technique.
- 9. The method according to claim 1, wherein the cantilever is a self-actuated cantilever.
- 10. A method of analyzing a sample in cyclical mode with a probe-based AFM, the method comprising:
providing a cantilever and a piezo-tube Z position actuator; oscillating the cantilever at a predetermined amplitude of oscillation so as to cause a tip of the cantilever to intermittently contact a surface of the sample; scanning the cantilever across the sample; generating a deflection signal in response to said scanning step; generating, with a first feedback loop, a cantilever control signal in response to the deflection signal; maintaining the amplitude of oscillation at a constant value in response to the cantilever control signal; using the cantilever control signal as an error signal in a second feedback loop to control the Z position actuator, wherein the first feedback loop is nested within the second feedback loop; damping the oscillating voltage with a active drive circuit to actively modify the quality factor (Q) of the cantilever resonant frequency during said scanning step; and wherein said damping step includes demodulating the deflection signal.
- 11. The method of claim 10, wherein said demodulating step includes using an amplitude detection circuit.
- 12. The method according to claim 11, wherein the amplitude detection circuit includes a gain stage.
- 13. 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 an active driving circuit; driving the self-actuated cantilever with the active driving circuit; 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; operating the active driving circuit to actively modify a quality factor (Q) associated with the self-actuated cantilever in response to the deflection signal; and wherein the active driving circuit demodulates the deflection signal and uses the demodulated deflection signal to modify said driving step.
- 14. An AFM for analyzing a surface of a sample, the AFM comprising:
a cantilever having a tip; an oscillator that oscillates said cantilever; and an amplitude detection circuit that actively modifies the quality factor (Q) associated with the cantilever in the amplitude domain and in response to the deflection signal to actively modify the bandwidth of amplitude detection of the AFM.
- 15. An AFM for analyzing a surface of a sample in cyclical mode, the AFM comprising:
a z-actuator; a cantilever having a tip for scanning the surface; an active driving circuit that includes an oscillator coupled to the cantilever to oscillate said cantilever; a deflection detection circuit that generates a deflection signal in response to deflection of the cantilever; and wherein said active drive circuit includes an amplitude detection circuit that actively modifies the quality factor (Q) associated with said cantilever in response to the deflection signal to actively modify the bandwidth of amplitude detection of the AFM in the amplitude domain.
- 16. The method according to claim 15, wherein said amplitude detection circuit generates an error signal based on said deflection signal.
- 17. The method according to claim 16, wherein the amplitude detection circuit includes a gain stage that applies a gain to the error signal to generate a modified deflection signal.
- 18. The AFM according to claim 17, wherein said oscillator generates an oscillating drive signal, and said amplitude detection circuit modulates the oscillating drive signal based on the modified deflection signal.
- 19. 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 an active driving circuit; driving the self-actuated cantilever with the active driving circuit; 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; operating the active driving circuit to actively modify a quality factor (Q) associated with the self-actuated cantilever in response to the deflection signal; and filtering an output of the active driving circuit with a band-pass filter.
CROSS-REFERENCE TO A RELATED APPLICATION
[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 09/476,163, filed on Dec. 30, 1999, which is a continuation in-part of U.S. patent application No. 09/280,160, filed on Mar. 29, 1999, each of these applications entitled ACTIVE PROBE FOR AN ATOMIC FORCE MICROSCOPE AND METHOD OF USE THEREOF, the latter of which is now issued as U.S. Pat. No. 6,189,374 B1 on Feb. 20, 2001.
Continuation in Parts (2)
|
Number |
Date |
Country |
Parent |
09476163 |
Dec 1999 |
US |
Child |
09904913 |
Jul 2001 |
US |
Parent |
09280160 |
Mar 1999 |
US |
Child |
09476163 |
Dec 1999 |
US |