Mercuric iodide (HgI2) polycrystalline films are being developed as a new photoconductor layer for direct converter X-ray
imaging detector. A physical vapor deposition (PVD) device for HgI2 deposition was developed specially.
Depending on the device and low purity (99.5%) low-cost HgI2 source material, polycrystalline HgI2 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 (00l), low dark current density less than 10 pA/mm2, high volume resistivity in the order
of 1013 Ω•cm and high X-ray response sensitivity of about 16 μC/(cm2•R), and the results put HgI2 polycrystalline films
in position as a leading candidate material for use in digital X-ray imaging system.
X-ray phase contrast imaging is a promising new technology today, but the requirements of a digital detector with large
area, high spatial resolution and high sensitivity bring forward a large challenge to researchers. This paper is related to
the design and theoretical investigation of an x-ray direct conversion digital detector based on mercuric iodide
photoconductive layer with the latent charge image readout by photoinduced discharge (PID). Mercuric iodide has been
verified having a good imaging performance (high sensitivity, low dark current, low voltage operation and good lag
characteristics) compared with the other competitive materials (α-Se,PbI2,CdTe,CdZnTe) and can be easily deposited on
large substrates in the manner of polycrystalline. By use of line scanning laser beam and parallel multi-electrode readout
make the system have high spatial resolution and fast readout speed suitable for instant general radiography and even
rapid sequence radiography.
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