Surface Sensitive Atomic Force Microscope Based Infrared Spectroscopy

Patent metadata

Field	Value
Publication number	US-2019011358-A1
Application number	US-201816030241-A
Country	US
Kind code	A1
Filing date	Jul 9, 2018
Priority date	Jul 6, 2017
Publication date	Jan 10, 2019
Grant date	—

Abstract

Systems and Methods may be provided for performing chemical spectroscopy on samples from the scale of nanometers with surface sensitivity even on very thick samples.

First claim

We claim:

1 . A method of obtaining a signal indicative of an infrared absorption spectrum of a thin surface layer of a sample with a probe of a scanning probe microscope, comprising the steps of:
a. Interacting the probe with a surface layer of the sample; b. Illuminating the surface layer with a beam of infrared radiation; c. Measuring a probe response comprising at least one of a resonance frequency shift and a phase shift of a resonance of the probe in response to infrared radiation absorbed by the surface layer; d. Measuring the probe response at a plurality of wavelengths of the infrared radiation; e. Constructing a signal indicative of infrared absorption of the surface layer.

2 . The method of claim 1 wherein the surface layer is disposed on a substrate that also absorbs IR radiation over the plurality of wavelengths.

3 . The method of claim 2 wherein the substrate is at least 10× thicker than the surface layer.

4 . The method of claim 2 wherein the substrate is at least 100× thicker than the surface layer.

5 . The method of claim 2 wherein the substrate is at least 800× thicker than the surface layer.

6 . The method of claim 2 wherein the signal indicative of the IR absorption of the surface layer is at least 5× stronger than residual absorption bands from the substrate.

7 . The method of claim 2 wherein residual absorption peaks from the substrate that appear in the signal indicative of the IR absorption of the surface layer are at least 8× smaller than absorption peaks measured on bare substrate without the surface layer. The method of claim 1 wherein the measuring probe response step comprises modulating an intensity of the beam of infrared radiation to induce an oscillatory response of the probe at or near a resonance of the probe.

8 . The method of claim 1 wherein the probe is oscillated at a frequency wherein there is a substantially maximum slope of probe oscillation phase with resonance frequency shift.

9 . The method of claim 1 wherein the measuring probe response step comprises oscillating the probe at or near a resonance of the probe with a piezoelectric actuator.

10 . The method of claim 1 wherein the measuring probe response step comprises modulating the probe at or near a resonance of the probe with an actuator comprising at least one of: an electrostatic drive, a magnetic drive, an acoustic drive, an ultrasonic drive, a photothermal drive, a bimetallic drive, and joule heating thermal drive.

11 . The method of claim 1 further comprising the step of linearizing the signal indicative of infrared absorption of the surface layer.

12 . The method of claim 12 wherein the linearizing step comprises compensating for at least one of: nonlinear dependence of sample elasticity with temperature, nonlinear dependence of probe resonant frequency with sample elasticity, and nonlinear dependence of probe oscillation phase with resonance frequency shift.

13 . The method of claim 12 wherein the linearizing step comprises measuring a probe response as a function of power of the beam of infrared radiation to create a linearization function.

14 . The method of claim 14 wherein measuring probe response as a function of IR beam power is used to infer a relationship between probe response and sample temperature rise.

15 . The method of claim 14 comprising the step of scaling the probe response at a plurality of wavelengths by the linearization function.

Assignees

• Bruker Nano Inc

Inventors

• Kjoller Kevin
• Prater Craig

Classifications

• G01Q60/32 Primary

  AC mode · CPC title

• G01Q30/02

  Non-SPM analysing devices, e.g. SEM [Scanning Electron Microscope], spectrometer or optical microscope · CPC title

• G01Q30/06

  for error compensation · CPC title

• G01N21/35 Primary

  using infrared light (G01N21/39 takes precedence) · CPC title

• G01Q30/04

  Display or data processing devices · CPC title