Micron-scale Direct-detection X-ray Detectors

Techniques such as high‐energy x‐ray microscopy and Bragg coherent diffraction imaging are being developed. These techniques provide unique structural information at the micro‐ and nano‐scale for the discovery of novel materials. However, due to the limitations of suitable detectors, these techniques are severely limited when applied at high x‐ray energies (> 30 keV). In particular, these techniques require detectors with micron‐ scale spatial resolution that are also efficient at the high x‐ray energies. Such detectors do not currently exist. To address this need, in this SBIR effort, we will manufacture large‐area high‐energy x‐ray detector arrays, with micron‐scale pixel resolution, with performance optimized for emerging applications that benefit from the coherence and higher brilliance available from emerging diffraction‐limited synchrotron light sources. Our approach directly sensitizes silicon CMOS imager readout integrated circuits (ROICs) with x‐ray‐sensitive colloidal quantum dot (CQD) nanocrystal detector films to realize robust high‐performance fine‐pixel‐resolution direct‐detection arrays. This approach eliminates both the need to manufacture large single‐crystal detector arrays and the need to perform die‐level hybridization of crystalline semiconductor detectors to the silicon readout circuits, which is difficult to do for micro‐scale detector pitches. In Phase I, we will manufacture a number of test arrays that demonstrate the performance of the CQD detector films for imaging greater than 30 keV X‐rays. Our effort will start with PbI2 nanocrystal detector structures, which we have previously shown effective for fabricating highly stable high‐ performance high‐energy x‐ray detectors. If deemed beneficial, we may also explore HgI2 nanocrystal detector films, or PbI2 / HgI2 heterostructures—we are experienced at manufacturing and integrating both into detectors. Detector test structures, consisting of simple field‐effect transistor (FET) structures and small‐sized arrays of various detector geometries, will be used to characterize performance and to demonstrate high conversion efficiencies and fine spatial resolution. Then, a 15‐micron 1K x 1K photovoltaic x‐ray imager will be fabricated and demonstrated. From their discovery to this day, X‐rays have been used for characterization of the spatial distribution of matter, imaging encompasses fields from medical applications to x‐ray microscopy and even crystallography. X‐rays are valued for their penetration power, their specificity of contrast, and their short wavelength underpinning the potential for high‐resolution microscopy. Emerging diffraction‐limited synchrotron light sources will increase the coherent flux up to a few orders of magnitude and reduce the horizontal beam divergence, which in turn will increase the brilliance enabling techniques that provide unique structural information at the micro‐ and nano‐scale, which will accelerate the pace for the discovery of novel materials that can impact every aspect of our daily lives, including the generation, transmission and use of energy.