Ultra-thin (<2 µm) silicon carbide free-standing membranes as beam position monitors for soft and tender X-ray beamlines

Conventional beam intensity monitor technologies, such as 'gold-meshes' and 'diamond conductive thin films', currently applied to tender and soft X-ray beams, encounter numerous application challenges, including diffraction effects, low signal strength, non-uniform transparency, and lack of position information. This study explores the potential of very thin (<2 μm) silicon carbide free-standing membranes, as in-line, minimally interfering beam intensity and position monitors, with high-lateral resolution, for soft and tender X-ray beamlines. Initial experimental assessments were conducted at the NanoMAX beamline at MAX IV to analyze the performance of such very thin devices in monitoring tightly focused (<1 μm FWHM) beams. The tests revealed that employing four-quadrant sensor layouts on such thin sensors resulted in significant charge collection losses in the regions between the quadrants and, under high electric field conditions, in charge multiplication effects (avalanche effects). Through Sentaurus TCAD theoretical simulations, the limitations of the four-quadrant design for such applications and the potential of an alternative technology (resistive X-ray beam postion monitor) were clarified.