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" /spl times/ 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/spl deg/C under high vacuum atmosphere (5 /spl times/ 10/sup -5/ mmHg) or under Ar pressure for 20 hours. Film thickness was measured by the X-ray transmission of 59.5 keV /sup 241/Am emission, giving values ranging from 90 to 130 /spl mu/m (5%). Film grain size was measured by scanning electron microscopy, and it gave an average of (50 /spl plusmn/ 20) /spl mu/m. Detectors were made with the films by depositing palladium as the front contact (contact area 4 mm/sup 2/) and then performing acrylic encapsulation.