Evaporated Metallic Contacts to Conducting Strontium Titanate Single Crystals

Abstract

Evaporated metallic contacts (area = 0.1 mm²) have been made to etched (100) surfaces of conducting strontium titanate single crystals. The metals employed were Mg, In, Au, Pd, and Pt. The electrical properties of these contacts were studied by measurements of: (1) differential capacitance as a function of bias voltage, (2) spectral variation of photoemission from the metal into the strontium titanate, and (3) current‐voltage characteristics. The measurements have been analyzed to yield effective values of Δφ (work function of the metal with respect to the strontium titanate conduction band at the contact) with the following results: (1) the electrical properties of the contacts are different for the different metals, (2) the low‐work‐function metals (Mg and In) form low‐resistance contacts, (3) the high‐work‐function metals (Au, Pd, and Pt) form blocking contacts, and (4) none of the blocking contacts can be characterized by a single value of Δφ; i.e., each blocking contact behaves as if it consists of patches of different Δφ.