Fabrication and characterization of large area mercuric iodide polycrystalline films

摘要

Mercuric iodide (HgI_2) polycrystalline films are being developed as a new photoconductor layer for direct converter X-ray imaging detector. A physical vapor deposition (PVD) device for HgI_2 deposition was developed specially. Depending on the device and low purity (99.5%) low-cost HgI_2 source material, polycrystalline HgI_2 films have been grown with dimensions Φ130 mm in diameter onto ITO-coated glass substrate. The grown techniques used can be easily extended to produce much larger films areas and the thickness of the grown layers, size of the grains and crystallinity can be regulated in a controlled way by adjusting the growth parameters. The basic physical characteristic, dark current and response characteristic to X-ray for the grown polycrystalline film were tested and the results show that the film has preferred crystalline orientation (001), low dark current density less than 10 pA/mm~2, high volume resistivity in the order of 10~(13) Ω·cm and high X-ray response sensitivity of about 16 μC/(cm~2·R), and the results put HgI_2 polycrystalline films in position as a leading candidate material for use in digital X-ray imaging system.