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1. WO2020117056 - SCANNING PROBE MICROSCOPE, SCAN HEAD AND METHOD

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Claims

1. A scan head for a scanning probe microscope arranged for moving a probe including a conductive cantilever relatively to a substrate surface, the head comprising:

- a first electrode positioned such that a capacitor is formed across a gap between the first electrode and a second electrode, wherein the second electrode is formed by the conductive cantilever;

- a voltage source for actuating the conductive cantilever by applying a voltage to the capacitor; and

- at least a first resistor arranged in series between the voltage source and one of the first and second electrodes such as to form an RC circuit for damping a vibration of the cantilever.

2. A scan head according to claim 1, wherein the resistor is arranged to provide a RC time suited to enhance damping of the held cantilever.

3. The scan head according to claim 1 or 2, wherein the resistance of the first resistor is adjustable.

4. The scan head according to any one of claims 1-3, wherein the first resistor is a tunable resistor; or

wherein the first resistor is a switchable resistor comprising an array of selectable resistors.

5. The scan head according to any one of claim 1-4, wherein the

capacitor is a parallel plate capacitor.

6. The scan head according to any one of claim 1-5, further

comprising a diode and second resistor arranged parallel to the first resistor.

7. The scan head according to any one of cl im 1-6, comprising a electronic read-out means connected to the RC circuit for determining a position of the cantilever, and wherein the scan

head preferably further comprises a decoupling capacitor that matches the capacitance between cantilever and first electrode.

8. The scan head according to any one of claims 1-7,

wherein the first electrode is optically transparent to enable optical read-out of cantilever position.

9. The scan head according to any one of claims 1-8

comprising a means to cool the first and/or first and second resistor to reduce thermal vibrational noise.

10. Method for moving a probe including a conductive cantilever

relatively to a substrate surface comprising:

positioning a first electrode such that a capacitor is formed across a gap between the first electrode and a second electrode, wherein the second electrode is formed by the conductive cantilever;

applying a voltage to the capacitor for actuating the conductive cantilever; and

providing at least a first resistor arranged in series between the voltage source and one of the first and second electrodes such as to form an RC circuit for damping a vibration of the cantilever.

11. The method according to claim 10, further comprising choosing, setting or selecting the resistance of the first resistor such that the characteristic RC time matches a resonance frequency of the cantilever by a factor within a range from 0.1 to 10 to improve damping of cantilever oscillations due to probing of step changes in said substrate surface.

12. The method according to claim 11, wherein the RC time matches a resonance frequency of the cantilever by a factor within 0.5 to 2, preferably close to 1 such as to operate the cantilever in a, or in a near critical damping mode.

13. The method according to any one of claims 10-12 for further probing the substrate surface using sub-resonant imaging with force control, wherein the method further comprises:

reducing a voltage applied to the capacitor for driving the conductive cantilever towards the surface of the substrate such that the conductive cantilever deflects;

measuring the cantilever position;

comparing the measured cantilever position with pre-recorded reference data obtained with the cantilever at a distance from the substrate with essentially zero interaction between cantilever and substrate, the data comprising the position of the cantilever as function of provided actuation voltage;

calculating an applied force to the substrate using the position deviation from the reference data and a spring constant of the provided cantilever;

closing a feedback loop that adjusts the voltage to control the force applied to the substrate using a force setpoint;

periodically adjusting the applied force setpoint.

14. A scanning probe microscope comprising the head according to any one of claims 1-9.

15. A probe holder for holding a conductive cantilever for use in a scanning probe microscope, the holder comprising a first electrode positioned such that a capacitor is formed across a gap between the first electrode and a second electrode, wherein the second electrode is formed by the conductive cantilever.

16. An assembly of a probe comprising a conductive cantilever and a scan head according to any one of claims 1-9.