Force measurement with real-time baseline determination

Patent metadata

Field	Value
Publication number	US-9910064-B2
Application number	US-201715438429-A
Country	US
Kind code	B2
Filing date	Feb 21, 2017
Priority date	Dec 7, 2013
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An atomic force microscope (AFM) and corresponding method to provide low force (sub-20 pN) AFM control and mechanical property measurement is provided. The preferred embodiments employ real-time false deflection correction/discrimination by adaptively modifying the drive ramp to accommodate to deflection artifacts.

First claim

The invention claimed is:

1. An AFM having a probe that interacts with a sample, the AFM comprising:
a scanner to position at least one of the probe and the sample at a location of interest of the sample;
a Z-axis scanner to move at least one of the probe and the sample to lessen a separation therebetween and cause the two to interact;
a detector to measure a deflection of the probe;
a processor to discriminate a deflection artifact from a deflection due to probe-sample interaction from the measured deflection data by continuously identifying a baseline during the moving step to derive an artifact free deflection and compare it with a predefined trigger force;
wherein the Z-axis scanner retracts the probe from the sample if the artifact free deflection substantially corresponds to the trigger force; and
wherein the processor determines the force between the sample and the probe, wherein the force is less than 20 pN.

2. The AFM of claim 1 , wherein the force is used as a trigger to change a parameter associated with the moving step.

3. The AFM of claim 2 , wherein the parameter is at least one of a speed, a direction and a force gradient.

4. The AFM of claim 1 , wherein the processor compares a drive ramp to a fit line based on data corresponding to the deflection, and further extrapolates the baseline based on the comparison.

5. The AFM of claim 4 , wherein the fit line is determined by performing a least squares fit.

6. The AFM of claim 5 , wherein the processor provides a rolling baseline until a threshold trigger is met.

7. An atomic force microscope (AFM) that detects a force between a sample and a probe of the AFM, the AFM comprising:
an actuator that positions the at least one of the probe and the sample at a location of interest of the sample;
a Z actuator that moves at least one of the probe and the sample to lessen a separation therebetween and cause the two to interact;
a detector that measures a deflection of the probe in response to the probe-sample interaction; and
a processor that uses the measured deflection, in real time as the Z actuator moves at least one of the probe and the sample, to determine an instantaneous baseline.

8. An atomic force microscope (AFM) including a probe that interacts with a sample, the AFM comprising:
an actuator that positions at least one of the probe and the sample at a location of interest of the sample;
a Z actuator that moves at least one of the probe and the sample to lessen a separation therebetween and cause the two to interact;
a detector that measures an observable interaction between the probe and the sample based on the moving step;
a processor that determines an observable interaction artifact from the observable interaction and derives an artifact free observable interaction, and wherein the processor compares the artifact free observable interaction with a trigger; and
wherein the Z actuator retracts the probe from the sample if the artifact free observable interaction substantially corresponds to the trigger.

9. The AFM of claim 8 , wherein the observable interaction includes at least one of a group including: force, deflection, electric interaction, magnetic interaction, thermal interaction and electromagnetic interaction.

10. The AFM of claim 9 , wherein the observable interaction is an electric interaction, and the electric interaction is one of force, current and voltage.

11. The AFM of claim 9 , wherein the electromagnetic interaction is based on scattered near field optical signals.

Assignees

• Bruker Nano Inc

Inventors

• Liu Changchun
• Pittenger Bede
• Hu Shuiqing
• Su Chanmin

Classifications

• G01Q10/065 Primary

  Feedback mechanisms, i.e. wherein the signal for driving the probe is modified by a signal coming from the probe itself · CPC title

• G01Q30/06

  for error compensation · CPC title

• G01Q10/06

  Circuits or algorithms therefor · CPC title