A new generation of direct X-ray detectors for medical and synchrotron imaging applications

Large-area X-ray imaging is one of the most widely used imaging modalities that spans several scientific and technological fields. Currently, the direct X-ray conversion materials that are being commercially used for large-area (> 8 cm × 4 cm without tiling) flat panel applications, such as amorphous selenium (a-Se), have usable sensitivities of up to only 30 keV. Although there have been many promising candidates (such as polycrystalline HgI2 and CdTe), none of the semiconductors were able to assuage the requirement for high energy (> 40 keV) large-area X-ray imaging applications due to inadequate cost, manufacturability, and long-term performance metrics. In this study, we successfully demonstrate the potential of the hybrid Methylammonium lead iodide (MAPbI3) perovskite-based semiconductor detectors in satisfying all the requirements for its successful commercialization in synchrotron and medical imaging. This new generation of hybrid detectors demonstrates low dark current under electric fields needed for high sensitivity X-ray imaging applications. The detectors have a linear response to X-ray energy and applied bias, no polarization effects at a moderate bias, and signal stability over long usage durations. Also, these detectors have demonstrated a stable detection response under BNL's National Synchrotron Light Source II (NSLS-II) 70 keV monochromatic synchrotron beamline.

Optical loss study of MPEOU-based polyceram planar waveguides

Sol-gel-derived polyceram materials based on organically modified silicon and titanium alkoxides have been synthesized in planar waveguide forms. They exhibit optical losses as low as <0.25 dB/cm and refractive indices as high as 1.685, coupled with exceptional ease of processing. The optical properties of the films (index of refraction, loss, and dispersion) are studied as functions of processing and composition, and the influence of chemistry on volume homogeneities and surface roughness of the films is investigated.

Organic-inorganic optical materials

We describe the use of an intriguing class of materials, termed polycerams, for applications in integrated optics. Polycerams are ceramic-polymer hybrid materials that are synthesized by wet-chemical methods. As films they can be deposited in single-step operations with thicknesses from <100 nm to >5 microm, and their refractive indices and Abbe numbers can be varied over a wide range. Polycerams synthesized as planar waveguides exhibit optical attenuations as low as <0.15 dB/cm, and they can be patterned by embossing. These materials exhibit exceptional optical properties that are due to combination of organic and inorganic constituents at the molecular level.