Evaporated Metallic Contacts to Conducting Cadmium Sulfide Single Crystals

Vapor deposited metallic contacts (area =̇1 mm2) have been made to oriented conducting cadmium sulfide crystals. The metals employed were Al, Ag, Cu, Pd, Au, and Pt. The electrical properties of these contacts have been studied by measurements of: (1) differential capacitance as a function of bias voltage, (2) current-voltage characteristics, and (3) spectral variation of photoemission from the metal into the cadmium sulfide. These measurements have been analyzed to yield values of Δφ (work function of the metal with respect to the cadmium sulfide at the contact) that are reproducible from contact to contact for a given metal and different for different metals. The relationship between Δφ, φm (work function of the metal in vacuum), and χ (semiconductor electron affinity), Δφ=φm−χ, is confirmed consistent with χ=̇4.0 volts for cadmium sulfide.