Pulsed laser deposition of laterally graded Ni/C-multilayers and their application in parallel beam X-ray optics

Since the end of the eighties Pulsed Laser Deposition (PLD) has been successfully used for the preparation of multilayers having X-ray optical quality. Outstanding features of the PLD-process are high thickness uniformity, precision of deposition process, formation of smooth interfaces and suppression of columnar thin film growth regime. In order to gain high quality layer stacks involving uniform thickness or graded thickness distributions across 4"-wafers the conventional thin film PLD-equipment has been modified. It provides a precise spatial control of the plasma plume orientation in the UHV deposition chamber. Layer stack morphology, interface roughness and reproducibility of period thickness in the total layer stack were characterized by means of grazing incidence X-ray reflectometry (Cu K alpha radiation) and HREM (High Resolution Electron Microscopy). PLD-Ni/C multilayers consisting of up to 75 double layers with period thicknesses between 3.0 nm and 5.5 nm show constant thickn ess gradients in the range of 0. 1 - 1.0 nm/cm across the total substrate length. A high reflectivity of up to 85 per cent and an excellent energy resolution are obtainable. For parallel beam X-ray optics these multilayers are bent to a parabolical shape. The performance of such PLD-manufactured Göbel-Mirrors is demonstrated by selected results.