High Frequency Deflection Measurement of IR Absorption

• US 20120050718A1
• Filed: 11/04/2011
• Published: 03/01/2012
• Est. Priority Date: 05/15/2007
• Status: Active Grant

• Current Assignee: Bruker Nano, Inc. (Bruker Corporation)
• Original Assignee: Anasys Instruments Corp. (Bruker Corporation)
• Inventors: Dazzi, A. Dazzi, Vodopyanov, Konstantin, Policar, Clotilde, Kjoller, Kevin, Prater, Craig, Reading, M.
• Granted Patent: US 8,418,538 B2
• Time in Patent Office: Days
• US Class Current: 356/51
• CPC Class Codes: B82Y 35/00 Methods or apparatus for measurement or analysis of nanostructures
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01Q 30/02 Non-SPM analysing devices, e.g. SEM [Scanning Electron Microscope], spectrometer or optical microscope
• CPC Class Codes: G01Q 60/32 AC mode

Abstract

An AFM based technique has been demonstrated for performing highly localized IR spectroscopy on a sample surface. Such a technique implemented in a commercially viable analytical instrument would be extremely useful. Various aspects of the experimental set-up have to be changed to create a commercial version. The invention addresses many of these issues thereby producing a version of the analytical technique that cab be made generally available to the scientific community.

Claims

1. In a system for measuring a localized IR spectra of a sample by interacting an AFM probe tip with a region of a sample, illuminating the sample with pulsed variable wavelength IR radiation at a pulse frequency, and collecting deflection data from the probe due to exciting a resonant oscillation of the probe in response to thermal expansion of the sample due to spectrally dependent absorption of radiation from the IR, a method for reducing background sensitivity, comprising;

applying a modulation signal to modulate the tip-sample interaction; and

,

using heterodyne techniques to measure the tip response due to IR absorption as a function of the IR source pulse frequency and the tip modulation frequency, thereby reducing the effect of background forces not localized to the tip.

2. The method of claim 1 comprising operating the AFM in tapping mode.