Atomic force and scanning tunneling microscopy study of current-voltage properties of TiB2 microcontacts

Scanning probe microscopy was used to investigate electrical microcontacts in the nanometer range, With the atomic force microscope current flowing through the contact as well as current-voltage characteristics of the contact as a function of the force acting on the contact itself were recorded. With the scanning tunneling microscope current-voltage characteristics and voltage at constant current characteristics were measured as a function of the contact position. From these experiments we conclude that a TiB2 microcontact can sustain a maximum voltage of about 0.1-1 V before melting. These results were confirmed by a theoretical model. The implications for the functioning of so-called positive temperature coefficient current limiting devices based on filled polymers is discussed. (C) 1997 American Institute of Physics.