This package will use high-resolution Raman and infrared (IR-SNOM) techniques to characterise and measure strain in very small-scale piezoelectric materials. Similar methods have been used before for this purpose but never to such high spatial resolution. As with the rest of the Nanostrain project, work package 2 aims to develop new tools and techniques for the characterisation of piezoelectric materials at the nanoscale to better understand materials that could provide future microelectronics. The package is led by PTB with NPL and XMaS as partners. Activities will be divided into 3 different sections. In the first section, which will be conducted by PTB-BS, micro-Raman spectroscopy is used to characterise and quantify strain in materials. Raman spectroscopy uses monochromatic (laser) light to excite particular vibrational and rotational transitions of single molecules and lattice vibrations of crystals to evaluate stress (which results in strain). Raman spectroscopy has previously been applied by PTB to identify defects in graphene layers and also for measuring stress in silicon-based samples. In this project, Raman spectroscopy will be used to measure the strain in piezoelectric materials resulting from applied voltage. Raman spectra can be collected from a very small area, less than 1 micrometer (1000 nm) in diameter. The second section of this package will use infrared scanning near-field optical microscopy (IR-SNOM) and nano-FTIR spectroscopy with broadband synchrotron radiation, to measure strain in these materials and will be conducted by the PTB-B team. Infrared spectroscopy is complimentary to Raman spectroscopy which is sensitive to the change of dipole moment during vibrations and how stress (or pressure) results in asymmetric stretch. Previously the achievable spatial resolution of spectroscopy was dictated by the diffraction and therefore by the wavelength of the incident beam. This limitation can be circumvented by applying near-field based techniques such as IR-SNOM capable of achieving a spatial resolution significantly below 100 nm. Additionally, by using broadband Synchrotron radiation, provided by the Metrology Light Source (MLS), nano-FTIR measurements can be performed over a much broader spectral range than by using conventional tuneable gas laser sources. This allows us to obtain much more detailed information about the properties of materials at the nanoscale. The last section of this package will provide a comparison between the two spectroscopic techniques and will be addressed near the end of the Nanostrain project. It will compare the results achieved by the different methods to evaluate which provides the highest sensitivity for strain characterization, and therefore which has the potential to have the biggest impact for new nanoscale piezoelectric materials. This will have wide-reaching implications, interesting both to the microelectronics industry but also materials scientists looking at characterising other materials on a nanoscale. For more information on Work Package 2, please contact Peter Hermann at: peter.hermann@ptb.de
