Bismuth tri-iodide polycrystalline films for digital X-ray radiography applications

Bismuth tri-iodide polycrystalline films were grown by the physical vapor deposition method. Glass 1" × 1" in size was used as the substrate. Palladium was deposited previously onto the substrates as the rear contact. For growth, bismuth triiodide 99.999% was heated at 130 - 170°C under high vacuum atmosphere (5 × 10^-5 mmHg) or under Ar pressure for 20 hours. Film thickness was measured by the X-ray transmission of 59.5 keV ²⁴¹Am emission, giving values ranging from 90 to 130 μm (5%). Film grain size was measured by scanning electron microscopy, and it gave an average of (50 ± 20) μm. Detectors were made with the films by depositing palladium as the front contact (contact area 4 mm²) and then performing acrylic encapsulation.