AFM-Raman and Tip Enhanced Raman studies of modern nanostructures Pavel Dorozhkin, Alexey Shchekin, Victor Bykov NT-MDT Co., Build. 167, Zelenograd Moscow, - презентация

1 AFM-Raman and Tip Enhanced Raman studies of modern nanostructures Pavel Dorozhkin, Alexey Shchekin, Victor Bykov NT-MDT Co., Build. 167, Zelenograd Moscow, Russia 5nm NT-MDT combines Atomic Force Microscope, Scanning Near Field Optical Microscope and Confocal Raman/Fluorescence Microscope in one experimental platform run by a single software. Individual nanoscale object can be studied simultaneously by many different techniques: AFM (up to 40 different measuring modes possible) and confocal Raman/fluorescence or SNOM. AFM maps provide information about topography and physical properties of the surface – mechanical electrical, magnetic, elastic etc. Raman imaging gives insight into the sample chemistry. When they are combined, extensive sample characterization becomes possible. AFM is integrated with optics in two different configurations: Inverted (based on commercial IOM) – for transparent samples and samples on microscope glass; Upright – for opaque samples. Dual scanning is realized: Scan by sample + scan by tip or Scan by sample + scan by laser spot. 1. Experimental setup – integrated AFM, optical microscope and confocal Raman/Fluorescence microscope 3. Tip Enhanced Raman Scattering – Raman maps with subwavelength lateral resolution F. E. Tip Enhanced Raman Scattering (TERS) on single-walled carbon nanotube (CNT) bundle (A),(B) AFM topography and line profile of the CNT bundle studied. Real height of the bundle is 5 nm. Observed width of the bundle is convolution of tip size. Some catalysis nanoparticles are attached to the bundle. (C) Searching for Hot Spot. Tip is scanned across the laser spot and Rayleigh (elastically scattered) light is recorded. Two hot spots where Rayleigh scattering reflection is maximum correspond to maximum interaction of light with localized surface plasmon at the end of the tip (this takes place in regions with maximum Z-polarization of electromagnetic field). TERS tip is then precisely positioned into one of the hot spots. Precision and temporal stability of tip positioning must be very high: nm. After that, sample is scanned to get TERS map (thanks to the Dual scan mode where both tip and sample can be scanned independently). (D) Intensity of Raman signal from CNT bundle as a function of tip-sample distance for two types of probes: gold coated AFM cantilever in tapping mode and etched Au wire with Shear Force (SFM) feedback. In Shear-force regime, Raman signal starts to increase when tip is only