Comparative study of atomic force mode and tunneling mode tip-enhanced Raman spectroscopy G. Picardi, Q. Nguyen, J. Schreiber and R. Ossikovski Eur. Phys. J. Appl. Phys., 40 2 (2007) 197-201 Published online: 31 October 2007 DOI: 10.1051/epjap:2007144