OPTICAL-PROPERTIES AND SURFACE-MORPHOLOGY STUDIES OF PALLADIUM CONTACTS ON MERCURIC IODIDE SINGLE-CRYSTALS

Palladium is chemically suitable for electric contacts on mercuric iod ide detectors for photon and nuclear radiation detection, so the under standing of palladium contacts is important for fundamental and practi cal scientific purposes. A study has been conducted on the surface mor phology of evaporated contacts using atomic force microscopy and optic al transmission and reflection. Evaporated palladium coatings are typi cally non-uniform and may deposit selectively on mercuric iodide surfa ce defects. Reflection measurements show that the coating thickness an d the surface treatment affect the intensity, position and shape of a reflected peak characteristic of the mercuric iodide structure. The re sults indicate that the band gap energy in the surface of the mercuric iodide is lowered by palladium contacts.