Quantitative Measurement of Local Infrared Absorption and Dielectric Function with Tip-Enhanced Near-Field Microscopy.
Scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared nanospectroscopy (nano-FTIR) are emerging tools for nanoscale chemical material identification. Here, we push s-SNOM and nano-FTIR one important step further by enabling them to quantitatively measure local dielectric constants and infrared absorption. Our technique is based on an analytical model, which allows for a simple inversion of the near-field scattering problem. It yields the dielectric permittivity and absorption of samples with 2 orders of magnitude improved spatial resolution compared to far-field measurements and is applicable to a large class of samples including polymers and biological matter. We verify the capabilities by determining the local dielectric permittivity of a PMMA film from nano-FTIR measurements, which is in excellent agreement with far-field ellipsometric data. We further obtain local infrared absorption spectra with unprecedented accuracy in peak position and shape, which is the key to quantitative chemometrics on the nanometer scale.
†CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.
Alexander A
AA
Govyadinov
†CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.
Iban
I
Amenabar
†CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.|‡Neaspec GmbH, 82152 Martinsried, Germany.
Florian
F
Huth
¶Department of Electrical and Computer Engineering and the Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, Illinois 61801, United States.
P Scott
PS
Carney
†CIC nanoGUNE Consolider, 20018 Donostia-San Sebastián, Spain.|§IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain.
Rainer
R
Hillenbrand
chemical identification; ellipsometry; infrared nanospectroscopy; nano-FTIR; near-field scattering; s-SNOM; thin films