Accessing the hidden lamellar nanostructure of semi-crystalline nascent polymers by small-angle X-ray scattering contrast variation

Most melt-crystallized polymers present a lamellar nanostructure of alternating crystalline and amorphous lamellae which is coherent enough to display a broad interference peak in small-angle X-ray scattering experiments (SAXS). Nascent semi-crystalline polymers, on the other hand, though highly crystalline, hardly show an interference peak. This has long been attributed either to the formation of extended chain crystals or to a highly incoherent lamellar stacking. Here it is shown that a coherent lamellar order is shaded by a large scattering contribution from the air/grain interface. This is revealed by a SAXS contrast variation technique that suppresses the air/grain interface scattering and leaves only the scattering contribution from the internal lamellae.

Properties Of SiC Film As X-Ray Mask Membrane

Many properties of LPCVD SiC film as X-ray mask membrane have been investigated in detail. The film has an atomic ratio of 1.0 and negligible impurities, and was found to be damage-free to SR X-rays up to 500 KJ/cm2. An integrated transparency of 1.05 μm thick SiC membrane for SR X-rays was measured to be 76%. The interference peak at 633 nm of optical spectrum has given the membrane of around 1.0 μm in thickness the transmittance peak of 70% and increased to more than 80% after an AR coating or planarizations by polishing and etching-back. The attainable transmittance was found to be limited to about 84%, theoretically and experimentally, due to the absorption of the membrane. The peak transmittance of 87% is obtainable by the AR coating on the polished SiC membrane. The internal stress was found to be independent of thicknesses above 0.6 μm and the measured Young's modulus is 4.5×1011 Pa irrespective of the thickness and stress. Some extremely polished (0.1 nm Ra) and all the etched-back membranes studied withstood breakage at the pressure as high as the as-deposited ones. The stress uniformity in 30 mm square of the membrane was found to be ± 10 % by measuring five local stresses with a bulge method.