ИСТИНА

Combination of high spatial resolution with chemical selectivity is an great demand for probing organic electronics materials. The maximum spatial resolution achievable in Raman microscopy is limited by approximately half the wavelength of the Raman excitation. Tip-enhanced Raman Spectroscopy (TERS) overcomes these limitations by combining scanning probe microscopy and Raman spectroscopy. TERS allows obtaining localized molecular vibrational information with a spatial resolution reaching 10 nm. Despite serious effort, TERS technique has not yet evolved to a commonly used spectroscopic method. Samples that can be efficiently studied by TERS are very limited. In organic electronics, where microscopic analysis with chemical selectivity at the nanometer scale is particularly in demand, practical implementation of TERS has met additional difficulties. Attempts to study organic bulk heterojunction materials using TERS microscopy were not successful because of tip degradation during the scanning. However, TERS was used to record of the local Raman spectra in selected points on the sample. In the present work, we used TERS to study bulk heterojunction morphology in ultrathin polymer-fullerene blends and semiconducting monolayers. We have evaluated two approaches to observe TERS in the scanning mode: a metal tip in the tunneling mode and a metallized AFM cantilever in the semi-contact mode. For each approach, we have optimized parameters of the scanning probe (material, hardness and radius). We optimized the fabrication of probes to achieve a tip radius less than 30nm. This allowed us to obtain a spectral map of P3HT:PCBM with submicrometer spatial resolution. Also we have successfully recorded a Raman spectrum of quaterthiophene siloxane dimer monolayer film by using TERS that can substantially increase the Raman signal. We discuss fabrication of probes, different approaches of measuring, and other issues related to TERS in organic electronics. Our results indicate that the TERS technique is a promising tool for organic electronics.