Polycrystalline Lead Iodide Films: Optical, Electrical and X-ray Counting Characterization

Abstract

AbstractLead iodide purified by zone refining and repeated sublimation was used for growing Polycrystalline films by physical vapor deposition. Palladium film was deposited as rear contact onto glass and alumina substrates 2.5 × 2.5 cm2 in size. Onto it, lead iodide polycrystalline films were grown by sublimation at 390 °C and 5 × 10−5 mm Hg, substrate temperatures of about 200 °C and deposition times of about 10 days. Film thickness was measured by X-ray transmission at 59.5 keV giving values from 35 to 50 μm (5%). Optical and atomic force microscopy were performed to the films giving an average grain size of (80±20) μm. Low temperature photoluminescence was performed and peak position and broadness confirmed the high purity of starting materials. Films were characterized by X-ray diffraction, giving an [ΣI (0 0 l)] / [ΣI (h k l)] relation of 0.8 that indicates a strong growth preferred orientation along c axis. Front palladium thermal deposition contacts and acrylic encapsulation were done and apparent resistivity (2 × 1014 Ω. cm) and current density (7 pA/cm2 (30 V)) were obtained. X-ray film response was checked by irradiating with 241Am and an X-ray beam. Finally, film and detector characterizations were correlated with starting material, deposition parameters and previous results for the same and alternative materials like mercuric iodide.