Peakforce Photothermal-Based Detection of IR Nanoabsorption

Abstract

An apparatus and method of performing photothermal chemical nanoidentification of a sample includes positioning a tip of a probe at a region of interest of the sample, with the tip-sample separation being less than about 10 nm. Then, IR electromagnetic energy having a selected frequency, ω, is directed towards the tip. Using PFT mode AFM operation, absorption of the energy at the region of interest is identified. calorimetry may also be performed with the photothermal PFT system.

What is claimed is: 
     
         1 . An apparatus for measuring IR nanoabsorption of a sample, the apparatus comprising:
 a probe interacting with the 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 mounted overhead of the probe for directing monochromatic light having a selected frequency, ω, towards a tip of the probe so as to produce a localized enhanced electric field between the tip and the sample;   a controller that determines a substantially instantaneous force between the probe and the sample from the detected motion of the probe and identifies a change in a mechanical property of the sample induced by the localized enhanced electric field; and   wherein a stiffness of the probe is greater than a stiffness of the sample.   
     
     
         2 . The apparatus of  claim 1 , wherein the the tip is metallized with a layer of one of Platinum Silicide and Platinum Iridium, and wherein the probe includes a cantilever having a spring constant between about 10-40 N/m. 
     
     
         3 . The apparatus of  claim 2 , wherein the probe is a silicon probe.