Probing Local Properties of Nanostructures with Non-contact Atomic Force Microscopy

In this talk, I will describe our experiments of using non-contact atomic force microscopy (AFM) to probe local properties of nanostructures. The AFM tip is used as a mobile gate to perturb samples locally and at the same time a sensor to detect minute electrostatic forces due to single electron charging (~ 10 /f/N). This technique allows us to track the charging process of a semiconducting carbon nanotube with high spatial and energetic resolution and provide a map of its local potential fluctuations. A further development combines local force sensing with Au nanoparticle electrometers to probe potential distribution inside a carbon nanotube. These Au nanoparticle electrometers are weakly coupled to the carbon nanotube through molecular junctions. I will demonstrate the operation of the Au nano-electrometers, determine the impedance of the molecular junction through quality factor measurements of the AFM cantilever and measure the potential profile in a looped nanotube.