Applications of scanning probe microscopy to data storage and Raman spectroscopy

Abstract

Scanning Probe Microscopy (SPM) has been proven to be a powerful tool for imaging and lithography with nanometer resolution. The application of SPM to data storage may produce aerial storage densities far greater than what is currently available. As an effort in this direction, the properties of reversible transitions on the molecular scale in a complex of 3-nitrobenzal malononitrile and 1,4-phenylenediamine have been studied, by application of local electric field pulses from a SPM probe. Current pulses injection during the operation of a conducting-tip tapping-mode atomic force microscope has also been developed. Combination of these two techniques should be of importance for MEMS-based data storage. Another effort of ours is to develop an experimental configuration by combining the analytical power of Raman spectroscopy with the nanometer resolution of atomic force microscopy (AFM). Here, an AFM silicon nitride probe, coated with a 40 nm silver layer, was used to significantly enhance the Raman signal by laser excitation of surface plasmons in the tip coating. Experimental results indicate a local surface enhanced Raman scattering (SERS) increase of 105. Lateral scanning of the sample and collecting the SERS signal allows for a 2D image of the chemical identity of the probed sample simultaneous with its topography as measured by the AFM. Also, the ratio of Stokes to anti-Stokes can be used to obtain an absolute map of the local temperature across the sample.