Monolithic integration of SiC diode detectors into scanning X-ray microscopy optical elements for in situ beam diagnostics

: Reliable monitoring of the incident X-ray beam intensity and position is essential in soft X-ray microspectroscopy, where beam instabilities directly affect data normalization and achievable spatial resolution. Conventional beam diagnostics are often implemented using offline detectors located far from the sample or by measuring downstream on empty regions of the sample support membrane, not fully reflecting the experimental conditions experienced during measurements. In this work, the development of functionalized soft X-ray optical elements based on monolithic silicon carbide (SiC) diode detectors, enabling real-time in situ beam diagnostics directly within a scanning transmission X-ray microscopy (STXM) setup, is presented. Two complementary device geometries are investigated: order-sorting aperture (OSA)-based detectors and center-stop-based detectors. The devices are fabricated using plasma-focused-ion-beam milling and substrate thinning, allowing the integration of optical and sensing functionalities with minimal changes to the beamline and endstation setup. The performance of the functionalized optics is experimentally validated at the PolLux STXM beamline of the Swiss Light Source. The devices provide simultaneous access to the transverse beam position and the incident beam intensity I0 through the unfocused 0th-order component. Using this component, the OSA detector enabled simultaneous measurements of the intensity and transverse displacement of the beam from the focused beam illuminating the sample. Between 700 and 1000 eV, the SiC measured current exhibited linear correlation to the avalanche photodiode (APD) signal, with coefficient of determination R2 = 0.997. Position-sensitive detection was possible with a four-sector diode, where all sectors were electrically continuous and beam responsive, while gaps between the quadrants were insensitive. These results demonstrate the feasibility of SiC-based functionalized X-ray optics as beam diagnostic tools for soft X-ray microscopy and spectroscopy.