Microscope having a multimode local probe, tip-enhanced raman microscope, and method for controlling the distance between the local probe and the sample

A multimode local probe microscope comprising:

• a resonator having an input first electrode and an output second electrode arranged on the resonator;
• excitation mechanism adapted to generate mechanical resonance in the resonator;
• a metal or metal-plated tip having an end of nanometer dimensions, the tip being fastened to the resonator;
• and
• movement mechanism for imparting relative movement between the resonator and a sample, the movement being adapted to bring the end of the tip up to a distance Z lying in the range 0 to 100 nm from the surface of the sample;
• wherein:
• said tip is electrically connected to said output second electrode, said output second electrode forming a common electrical contact point for collecting firstly a first electrical signal representative of friction forces between the end of the tip and the surface of the sample, and secondly a second electrical signal relating to a tunnelling current between the end of the tip and the surface of the sample;
• and
• in that the microscope includes:
• amplifier electrically connected to said output second electrode, said amplifier being adapted to amplify the second signal relating to the tunnelling current;
• processor adapted to process separately firstly the first signal relating to friction forces and secondly the second signal relating to the tunnelling current;
• and
• regulator adapted to regulate the distance Z between the end of the tip and the surface of the sample, regulation in a first mode being as a function of the first signal representative of friction forces, and regulation in a second mode being as a function of the second signal relating to the tunnelling current.