AFM-IR for quantitative nanoscale chemical analysis

Santa Barbara, CA – A new paper authored by Dr Andrea Centrone and his colleagues at the National Institute of Standards and Technology (NIST) reported on experiments that carefully studied the AFM-IR signal strength versus sample thickness. The experiments showed that the AFM-IR signal increases linearly with thickness for samples up to 1µm thick. This observed linearity may pave the way for quantitative chemical analysis at the nanoscale.

AFM-IR enables chemical identification and imaging with nanoscale resolution. In this paper, published recently in Small, a publication which focuses on the nano and micro worlds, the researchers reports on electron beam nanopatterned polymer samples which were fabricated directly on zinc selenide prisms and used to experimentally evaluate the AFM-IR signal lateral resolution, sensitivity and linearity. The authors have shown that the AFM-IR lateral resolution for chemical imaging is comparable to the lateral resolution obtained in the AFM topography. Spectra and chemical maps were produced from samples as thin as 40 nm. The observations also provide experimental confirmation of theoretical predictions on AFM-IR previously developed by Prof Alexandre Dazzi of University of Paris-Orsay who is also the inventor of the technique. The patented AFM-IR technique is available commercially as the nanoIR platform from Anasys Instruments, Santa Barbara, CA. In AFM-IR, a rapidly pulsed infrared (IR) laser is directed on upon a thin sample which absorbs the IR light and undergoes rapid thermomechanical expansion. An AFM tip in contact with the sample resonates in response to the expansion, and this resonance is measured by the AFM.