Plasmonic-enhanced infrared photoexpansion nano-spectroscopy using tunable quantum cascade lasers

Feng Lu; Mikhail A. Belkin

doi:10.1117/12.929192

11 October 2012 Plasmonic-enhanced infrared photoexpansion nano-spectroscopy using tunable quantum cascade lasers

Feng Lu, Mikhail A. Belkin

Proceedings Volume 8466, Instrumentation, Metrology, and Standards for Nanomanufacturing, Optics, and Semiconductors VI; 84660I (2012) https://doi.org/10.1117/12.929192
Event: SPIE NanoScience + Engineering, 2012, San Diego, California, United States

Abstract

Mid-IR photoexpansion nano-spectroscopy measures spectra of samples on nanoscale by detecting local thermal expansion associated with light absorption using a standard atomic force microscope (AFM). Cantilever deflection is directly proportional to sample absorption. This method results in a simple experimental setup with no optical detectors. We have recently demonstrated that the sensitivity of photoexpansion nano-spectroscopy can be dramatically enhanced by moving the laser pulses repetition frequency in resonance with the mechanical frequency of the AFM cantilever. We were able to produce spectra from ~100 nm thin films using low energy (4 nJ) pulses from a tunable quantum cascade laser (QCL). The spatial resolution, which is determined by thermal diffusion length, has been demonstrated to be better than 50 nm. Sample heating is limited to ~10 mK. Here we present a novel approach to increase both the sensitivity and spatial resolution of photoexpansion nano-spectroscopy. We utilize the plasmonic local-intensity enhancement below a gold-coated AFM tip. We successfully produced high quality vibrational absorption spectra from samples as thin as 10 nm positioned on top of gold-coated silicon substrates. In addition to higher photoexpansion signal, our technique features higher spatial resolution, which is no longer limited by thermal diffusion length but is instead determined by the dimensions of the high-intensity field region below the metal tip, which can be 10 nm or smaller.

Citation Download Citation

Feng Lu and Mikhail A. Belkin "Plasmonic-enhanced infrared photoexpansion nano-spectroscopy using tunable quantum cascade lasers", Proc. SPIE 8466, Instrumentation, Metrology, and Standards for Nanomanufacturing, Optics, and Semiconductors VI, 84660I (11 October 2012); https://doi.org/10.1117/12.929192

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available