16| PLASTICS ENGINEERING | OCTOBER 2011| www.4spe.orglaser as the light source, and thespectral coverage of laser-based lightsources is still limited. Now,researchers from the BasqueNanoscience Research Center, CICnanoGUNE (San Sebastian, Spain),and Neaspec GmbH have developeda novel near-field spectroscopy plat-form with a thermal source.3"Theinstrument that we call nano-FTIRallows the recording of broadbandinfrared spectra with nanoscale spa-tial resolution," says RainerHillenbrand, leader of theNanooptics group at nanoGUNE.The new setup could be used to ana-lyze polymer nanocomposites with100 to 1000 times better resolutionthan conventional Fourier-transforminfrared (FTIR) spectroscopy.Because the technique is based onatomic force microscopy (AFM), itsimultaneously provides topographicinformation about the sample's sur-face, says Hillenbrand. As the sharpmetallic AFM scans a sample sur-face, it is illuminated with theinfrared light from a thermal source.Acting like an antenna, the tip con-verts the incident light into ananoscale infrared spot at the tipapex. By analyzing the scatteredinfrared light with a speciallydesigned FTIR spectrometer, theresearchers can record infrared spec-tra from ultra-small sample volumes."Our technique allows for recordingspectra in the near-to-far-infraredspectral range. These spectra can beused to chemically identify the com-posite components by their specificinfrared 'fingerprint' spectrum,"Hillenbrand explains.They expect that polymer sampleswill have weaker signals than thesamples of silicon and oxides theyhave studied so far. The current ver-sion of the instrument could be usedfor chemical mapping of thin poly-mer films with a resolution betterthan 100 nm and an imaging time ofa few hours. "By improving the sig-nal-to-noise in the spectra with theuse of more powerful thermal sources(e.g. operating at increased tempera-ture) and optimized near-field probes,we aim on rapid spectroscopic imag-ing with a resolution in the 10-nmrange," says Hillenbrand. With suchimprovements, the researchers thinkthat the instrument will provide away to identify and analyze polymerswith nanoscale spatial resolution,broad spectral coverage, and a lightsource that is relatively simple andinexpensive.References1. H.S. Choi et al, "Studying polymer thinfilms with hybrid optical microcavities,"Optics Letters, Vol. 36, No. 11, 2152-54(June 1, 2011).2. V. Lauter et al, "Morphology of thinnanocomposite films of asymmetricdiblock copolymer and magnetitenanoparticles," Journal of Physics:Condensed Matter, Vol. 23, 254215 ff.(2011).3. F. Huth et al, "Infrared-spectroscopicnanoimaging with a thermal source,"Nature Materials,Vol. 10, pp. 352-56(May 2011). For infrared nanospectroscopy with a thermal source, an atomic force microscopetip probes a sample. The tip is illuminated with the broadband infrared radiation froma thermal source and the backscattered light is analyzed with a Fourier-transformspectrometer, yielding local infrared spectra with a spatial resolution better than 100nm. The displayed graph shows local infrared spectra of differently processed oxidesin an industrial semiconductor device. Copyright F. Huth, CIC nanoGUNE.