Nanoscale infrared spectroscopy instrument gets a boost by a thermal source

An instrument that allows for recording infrared spectra with a thermal source at a resolution that is 100 times better than conventional infrared spectroscopy is now possible, thanks to a development by researchers from CIC nanoGUNE and Neaspec GmbH.

An instrument that allows for recording infrared spectra with a thermal source at a resolution that is 100 times better than conventional infrared spectroscopy is now possible, thanks to a development by researchers from CIC nanoGUNE (San Sebastian, Spain) and Neaspec GmbH (Munich, Germany). The technique could be applied for analyzing the local chemical composition and structure of nanoscale materials in minerals or biological tissue, as well as in polymer composites and semiconductor devices.

Conventional optical instruments, such as Fourier transform infrared (FTIR) spectrometers, cannot focus light to spot sizes below several micrometers, preventing infrared-spectroscopic mapping of single nanoparticles, molecules or modern semiconductor devices. But researchers at nanoGUNE and Neaspec have now developed an infrared spectrometer that allows for nanoscale imaging with thermal radiation—nano-FTIR—which is based on a scattering-type near-field microscope (NeaSNOM) that uses a sharp metallic tip to scan the topography of a sample surface. While scanning the surface, the tip is illuminated with the infrared light from a thermal source. Acting like an antenna, the tip converts the incident light into a nanoscale infrared spot (nanofocus) at the tip apex. By analyzing the scattered infrared light with a specially designed FTIR spectrometer, the researchers were able to record infrared spectra from ultra-small sample volumes.

The researchers were able record infrared images of a semiconductor device from Infineon Technologies AG (also of Munich, Germany), achieving spatial resolution better than 100 nm and demonstrating that thermal radiation can be focused to a spot size that is hundred times smaller than in conventional infrared spectroscopy, says Florian Huth, who performed the experiments. Huth also demonstrated that nano-FTIR can be applied for recognizing differently processed silicon oxides or to measure the local electron density within complex industrial electronic devices.

Nano-FTIR could also—based on vibrational fingerprint spectroscopy—be applied for nanoscale mapping of chemical composition and structural properties of organic and inorganic nano-systems, including organic semiconductors, solar cells, nanowires, ceramics and minerals, according to Huth.

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Posted by Lee Mather

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