Current-voltage and imaging of TiSi ₂ islands on Si(001) surfaces using conductive-tip atomic force microscopy

Using conducting tip atomic force microscopy (c-AFM), we have measured the current-voltage (I-V) characteristics of individual submicron islands of TiSi ₂ on Si(100) surfaces, and we have developed an imaging approach that distinguishes the electrical properties of the islands. The Schottky barrier height (SBH) of the submicron TiSi ₂ islands was deduced from the I-V measurements. The results indicate that there is a significant variation of SBH among the islands on the same surface. The measurements employ a conventional AFM with a heavily B-doped diamond tip to obtain the current-voltage relations. In contact mode AFM, electrical signals are extracted independently from the topographic image. In addition, we have modified the imaging method to probe the local electrical properties of a surface with regions of different conductivity. Using a lock-in technique both phase and amplitude images were obtained, and the resultant image is essentially a map of the differential surface conductivity. Using this method, TiSi ₂ islands on a Si(100) surface were imaged. This approach can be readily extended to other materials systems.