PHYSICAL-PROPERTIES OF THE X-RAY MEMBRANE MATERIALS

Over the last ten years, the materials most used for x-ray membrane ap plications have been boron nitride, silicon, silicon nitride, silicon carbide, and diamond. This work presents a review of the macroscopic p roperties (roughness, biaxial Young's modulus, optical transmission, f racture strength, and radiation hardness) of these materials. From an examination of the overall criteria, it can be concluded that silicon carbide and diamond continue to be the potential material candidates, even if few properties of diamond membranes have still to be improved. On the other hand, to optimize the physical properties of the membran e material, one has to understand the relationship between the macrosc opic characteristics of the membrane and its microstructure. To this a im, we have studied two types of SiC membrane materials, namely, (i) p lasma enhanced chemical vapor deposited a-SiC:H and (ii) laser ablatio n deposited a-SiC. The microstructural characterizations were carried out by means of x-ray diffraction, x-ray photoelectron spectroscopy, F ourier transform infrared spectroscopy, and elastic recoil detection a nalysis techniques. We were thus able to (i) point out the role of C-H and Si-H hydrogenated bonds and Si-C bonds in the stress evolution, f rom compressive to tensile, (ii) demonstrate the linear dependence of the biaxial Young's modulus upon the Si-C bond density and (iii) show the effect of dangling bonds on the optical transmission.