Peakforce photothermal-based detection of IR nanoabsorption

1. A method of locally measuring IR absorption of a sample, the method comprising:

causing a probe to interact with a sample in an oscillating mode of AFM operation;

directing a locally amplified IR signal toward a sample; and

identifying a change in modulus based on the directing step;

and wherein the oscillating mode uses feedback to control the interaction between the probe and the sample, and wherein the feedback is based on a localized detected force between the probe and the sample in each oscillation cycle.

2. The method of claim 1 , wherein the oscillating mode is peak force tapping (PFT) mode.

3. The method of claim 1 , wherein the oscillating mode is contact resonance mode.

4. The method of claim 1 , further comprising tuning the IR signal over a range of frequencies to obtain a spectrum of the sample.

5. The method of claim 1 , further comprising an optical element focusing the IR signal on a tip of the probe.

6. The method of claim 1 , further comprising determining a ΔT.

7. The method of claim 6 , further comprising determining a mass by obtaining 3D topography data corresponding to a region in response to the directing step.

8. A method of photothermal chemical nanoidentification of a sample, the method comprising:

positioning a tip of a probe at a region of interest of the sample, the tip-sample separation being less than about 10 nm;

directing IR electromagnetic energy having a selected frequency, ω, towards the tip; and

using PFT mode of AFM operation to identify absorption of the energy at the region of interest.

9. The method of claim 8 , further comprising obtaining a spectrum of the sample by tuning the selected frequency to a range of frequencies.

10. The method of claim 9 , wherein absorptions of energy over the range of frequencies are acquired on a sub-millisecond timescale for at least a 20×20 nm sample area.

11. The method of claim 8 , further comprising determining an elastic modulus Y for the region of interest based on the absorption of energy.

12. The method of claim 8 , further comprising focusing the IR electromagnetic energy towards the tip using a lens.

13. The method of claim 8 , wherein the probe is metalized with at least one of Platinum Iridium and Platinum Silicide.

14. The method of claim 8 , further comprising directing the IR electromagnetic energy from a tunable monochromatic source operating in a pulsed mode with a line width below 1 cm −1 and a peak power of at least 1 mW.

15. The method of claim 8 , further comprising:

determining a ΔT based on the absorption of energy; and

determining a mass of the region of interest by obtaining 3D topography data corresponding to the region of interest.

16. A scanning probe microscope (SPM) comprising:

a probe interacting with a sample in an oscillating mode;

that uses feedback to control the interaction between the probe and the sample, and wherein the feedback is based on a substantially instantaneous force on the probe in each oscillation cycle;

a position detector for detecting a motion of the probe;

a monochromatic light source for directing monochromatic light having a selected frequency, ω, towards a tip of the probe;

an oscillating mode force detection block for determining a substantially instantaneous force between the probe and the sample from the detected motion of the probe; and

a controller in communication with the oscillating mode force detection block and operable to identify a change in a mechanical property of the sample induced by a localized enhanced electric field between the tip and the sample.

17. The SPM of claim 16 , wherein the oscillating mode is PFT Mode.

18. The SPM of claim 16 , wherein the tip radius is 50 nm or less.

19. The SPM of claim 18 , wherein the probe comprises at least one of doped Silicon and Diamond.

20. The SPM of claim 16 , wherein the monochromatic light source is a tunable External Cavity Quantum Cascade Laser (QCL).