Soft X-ray Detectors Based on SnS Nanosheets for the Water Window Region

The structural characteristics of biological specimens, such as wet proteins and fixed living cells, can be conveniently probed in their host aqueous media using soft X-rays in the water window region (200-600 eV). Conventional X-ray detectors in this area exhibit low spatial resolution, have limited sensitivity, and require complex fabrication procedures. Here, many of these limitations are overcome by introducing a direct soft X-ray detector based on ultrathin tin mono-sulfide (SnS) nanosheets. The distinguishing characteristic of SnS is its high photon absorption efficiency in the soft X-ray region. This factor enables the fabricated soft X-ray detectors to exhibit excellent sensitivity values on the order of 104 mu CGyVac-1 cm-2 at peak energies of approximate to 600 eV. The peak signal is found to be sensitive to the number of stacked SnS layers, with thicker SnS nanosheet assemblies yielding a peak response at higher energies and with peak sensitives of over 2.5 x 104 mu CGyVac-1 cm-2 at 1 V. Detailed current-voltage and temporal characteristics of these detectors are also presented. These results showcase the excellent performance of SnS nanosheet-based soft X-ray detectors compared to existing direct soft X-ray detectors, including that of the emerging organic-inorganic perovskite class of materials.