Method of making a force curve measurement on a sample
View Patent ↗A force scanning probe microscope (FSPM) and associated method of making force measurements on a sample includes a piezoelectric scanner having a surface that supports the sample so as to move the sample in three orthogonal directions. The FSPM also includes a displacement sensor that measures movement of the sample in a direction orthogonal to the surface and generates a corresponding position signal so as to provide closed loop position feedback. In addition, a probe is fixed relative to the piezoelectric scanner, while a deflection detection apparatus is employed to sense a deflection of the probe. The FSPM also includes a controller that generates a scanner drive signal based on the position signal, and is adapted to operate according to a user-defined input that can change a force curve measurement parameter during data acquisition.
1. A method of making a force curve measurement on a sample, the method comprising:
measuring a force on a probe as the probe interacts with a sample in response to a user-defined input;
comparing the force to a set-point;
using a feedback loop to maintain the force at the set-point; and
adjusting the set-point according to the user-defined input, wherein the user-defined input defines at least one of multiple approach moves and multiple retract moves in one cycle.
2. The method of claim 1 , wherein said measuring step includes detecting motion of the probe.
3. The method of claim 1 , wherein the user-defined input is a path defined by force versus time.
4. The method of claim 1 , further including the step of determining a force gradient based on said measuring step performed for at least two points in time.
5. The method of claim 1 , further including producing relative motion between the probe and the sample in response to the user-defined input, the user-defined input defining intended motion in a direction generally orthogonal to a surface of the sample.
6. The method of claim 5 , wherein said producing step is interrupted prior to said adjusting step.
7. The method of claim 1 , wherein said measuring step is performed for at least two points in time, and said adjusting step is performed in response to a predetermined change in the force.
8. The method of claim 1 , wherein the user-defined input is an automatic input.
9. The method of claim 1 , wherein the user-defined input is defined by probe position versus time.
10. A method of making a force curve measurement on a sample, the method comprising:
measuring a force on a probe as the probe interacts with a sample in response to a user-defined input;
comparing the force to a set-point;
using a feedback loop to maintain the force at the set-point; and
adjusting the set-point according to the user-defined input, wherein said producing step is performed by a sensored Z stage.
11. The method of claim 10 , wherein said sensored Z stage is coupled to a piezoelectric tube scanner, said tube scanner providing scanning motion in a plane substantially orthogonal to the third axis.