High resolution imaging of contact potential difference using a novel ultrahigh vacuum non-contact atomic force microscope technique

An ultrahigh vacuum scanning Kelvin probe force microscope (UHV SKPM) based on the gradient of electrostatic force was developed using the technique o f a UHV non-contact atomic force microscope (NC-AFM) capable of atomic leve l imaging, and used for simultaneous observation of contact potential diffe rence (CPD) and NC-AFM images. The CPD images with a potential resolution o f less than 10 meV were observed in the UHV SKPM, demonstrating an atomic l evel resolution. The change of potential corresponding to the charges on th e insulated surface of polypropylene have been observed in UHV SKPM. We als o demonstrated a reliable method to obtain the CPD from the bias voltage de pendence curves of the frequency shift in all of the scanning area. The res ults are consistent with comparing the barrier height images in that the wo rk functions of adatoms are greater than the work function of corner holes. (C) 1999 Elsevier Science B.V. All rights reserved.