Abstract: An element adapted for at least one use selected from high energy radiation detection, imaging and barrier use, which includes a planar substrate on a surface of which there is a layer polycrystalline mercuric iodide, which has been deposited from the vapor phase, having a thickness within the range of from more than 0.5 mm and up to about 10 mm. A process for preparing an element having such thicknesses. A planar substrate, having deposited on a surface thereof, a layer of mercuric iodide in at least two discrete adjacent sub-layers having a total thickness within the range of from greater than 0.5 mm to about 10 mm. A system adapted for at least one purpose selected from radiation detection, radiation imaging and high energy absorption, which includes an element having thicknesses as described above.