Electrical Characterization of TiSi2 Nanoscale Islands by Scanning Probe Microscopy

Abstract

Using conducting tip atomic force microscopy (c-AFM), we have measured thecurrent voltage characteristics of individual sub-micron islands of TiSi2 on Si(100)surfaces and we have developed an imaging approach that distinguishes the electricalproperties of the islands. The Schottky barrier height (SBH) of the sub-micron TiSi2islands was deduced from the I-V measurements. The results indicate that there is asignificant variation of SBH among the islands on the same surface. The measurementsemploy a conventional AFM with a heavily B-doped diamond tip to obtain the currentvoltagerelations. In contact mode AFM, electrical signals are extracted independentlyfrom the topographic image. In addition, we have developed a new imaging method toprobe 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 theresultant image is essentially a map of the differential surface conductivity. Using thismethod, TiSi2 islands on a Si(100) surface were imaged. This approach can be readilyextended to other materials systems.Nanoscale TiSi2 islands of lateral diameter of ~5 nm are formed by electron beamdeposition of a few monolayers of titanium on atomically clean Si(111)7x7 surfacefollowed by in situ annealing at high temperatures (800-1000°C). Direct probing of theelectrical characteristics of these islands was performed using ultra high vacuumscanning tunneling microscope (UHV-STM) and scanning tunneling spectroscopy (STS).