The invention of the Scanning Tunnelling Microscope (STM) at the beginning of the eighties opened the way to a number of experimental techniques for characterizing surfaces at nanometre scale or below (Atomic Force Microscopy (AFM), Photon Scanning Tunnelling Microscope (PSTM), Scanning Near Field Optical Microscope (SNOM)…) These instruments involve many fundamental physical phenomenons which deserve detailed studies. The probe-sample junction possesses unique physical characteristics, confinement, symmetry breaking, high electric field, evanescent electromagnetic waves, localized coupled oscillation modes. The work reported in this part is devoted to the study of some of these physical phenomenons.
In the so-called “non-contact” or “frequency modulation” mode, the AFM uses the shift of the resonance frequency of the cantilever under the influence of the tip-sample forces to control the tip-surface distance. The cantilever oscillation is maintained at its resonance frequency by a positive, constant amplitude, feedback loop. This technique is well suited for the high quality factor cantilevers that are used in UHV studies. It has proven to be capable of true atomic resolution on metallic, semi-conducting and insulating surfaces. Our main objective is to image and manipulate individual molecules on insulating surfaces for applications in molecular electronics and nanosciences. Two UHV-AFM heads are operating in CEMES : -A modified VT AFM/STM from Omicron Nanotechnology that was modified to allow dynamic nanostencil experiments. -A RT AFM/STM from Omicron Nanotechnology whose primary use is high resolution NC-AFM studies. This head was greatly improved by changing the original light source to a superluminescent laser. - A modified LT STM that could be used to perform nc-AFM using tuning forks (Q+)
Fundings
PAMS (EU project)
