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Accurate detection of x-ray radiation is essential for tissue equivalence detection and safety control during medical radiotherapy. Here, a promising radiation detector based on organic 1,8-naphthalimide (C12H7NO2, NTI) single crystals is proposed. NTI single crystals with dimensions of 8 × 2 × 1 mm3 were synthesized by an optimized solvent-cooling method, and the crystal structure was characterized to elucidate the anisotropy mechanism. The coplanar detector made by NTI has a leakage current of less than 0.1 pA at an electric field strength of 1 kV cm−1 and provides excellent detection of 5.49 MeV α-particles (241Am) with a full-energy peak resolution of up to 32.3%. The calculated electron mobility (μ e) and electron mobility-lifetime product (μ τ)e were 7.9 cm2 V−1s−1 and 1.56 × 10−6 cm2 V−1, respectively. Additionally, the detection limit of the NTI detector was 0.35 µGy s−1 in the electric field strength range of 0.2–1.0 kV cm−1 under a 20 kV x-ray beam with a high sensitivity of 56.2 μC Gy−1cm−2. Consequently, the NTI detector achieves an excellent spatial resolution of 0.8–0.9 lp mm−1 in terms of x-ray imaging capability. [ABSTRACT FROM AUTHOR]

Soft x-ray detectors play crucial roles in biology, chemistry, and lithography. Current soft x-ray detectors suffer from insufficient responsivity (R), excessively large cell area, and limited stability. Here, the β-Ga2O3 soft x-ray detector is constructed, and the effects of varying the sensitive layer thickness and voltage on the soft x-ray detection characteristics of the device are explored. Meanwhile, the mechanism of the multiplication ionization process from soft x-ray and the photoconductivity gain on the photoresponse performance of the device are analyzed. The device obtains the R up to 3.05 × 103 A/W under 300 eV soft x-ray irradiation at the synchrotron beamline, which is about 1.19 × 104 times higher than that of the conventional device. The Ga2O3 device also maintains stable operation under long-term irradiation and multicycle switching. These results indicate that Ga2O3 is an ideal candidate material for soft x-ray detection, which has great potential for applications such as imaging of biological cells. [ABSTRACT FROM AUTHOR]

The recently reported two-dimensional lead halide perovskites have attracted much attention in high-energy radiation detector applications due to its high structural stability and low ion migration. However, the increased exciton binding energy and the charge transport barrier resulting from the A-site cation can easily limit the charge extraction and device performance. As an emerging material in high-energy detection field, guanidinium {GA+ = [C(NH2)3]+} is a relatively large organic cation composed of three amino groups, which can enhance the hydrogen bond formation and the van der Waals interactions with the metal halide framework. Meanwhile, the polymer symmetry of GA+ cation leads to almost zero dipole moments, excellent electronic properties, and high thermodynamic stability. However, there is a lack of report on the preparation, structure, and properties of GA-based 2D perovskite single crystals as well as their applications in x-ray detection. Herein, we have synthesized large-size two-dimensional GA2PbI4 single crystals with a bandgap of 2.28 eV by cooling crystallization and applied them to x-ray detectors. GA2PbI4 single crystals exhibit a high μτ product of 7.5 × 10−4 cm2 V−1 and a low trap density of 6.44 × 108 cm−3. An effective x-ray photoresponse was realized with a sensitivity as high as 392.4 μC Gyair−1 cm−2. The unique structure and excellent charge transport properties of GA+ organic cations exhibit promising prospects in high-performance x-ray detection. [ABSTRACT FROM AUTHOR]

Metal halide perovskites have emerged as promising candidates for x-ray detection; in particular, the in-direct detectors based on perovskite scintillators have demonstrated appealing performance metrics. However, both perovskite thin films and nanocrystals still suffer from poor stability. In this work, we introduce a heterovalent cation exchange strategy to effectively modulate the optoelectronic properties of perovskite nanocrystals and further enhance their stability. Here, a portion of Pb2+ in perovskite nanocrystals was replaced with lead-free Sb3+. This is a versatile method that can be applied to cation exchange of various perovskite nanocrystals, such as CsPbX3 and FAPbX3, allowing for the synthesis of a wide range of mixed-cation perovskite compositions. The resulting nanocrystals exhibit relatively high photoluminescence quantum yields and improved thermal stability and water resistance. The Sb@CsPbBr3 nanocrystals also demonstrated great potential for x-ray detection as scintillators with fast response, bright and radioluminescence, and excellent image quality. [ABSTRACT FROM AUTHOR]

Owing to the large x-ray attenuation coefficient, appropriate bandgap, high resistivity, and high mobility-lifetime (μτ) product, binary II–VI semiconductor CdSe is a promising x-ray detection material and it has exhibited excellent x-ray detection at room temperature (RT). For further improving the characteristics of CdSe x-ray detectors, the electrical properties of CdSe single crystals (SCs) grown through the pressure-assisted vertical Bridgman method and their x-ray detection performance have been investigated at RT and liquid nitrogen temperature (LNT), respectively. The significantly enhanced x-ray photocurrent and the prolonged response time of the devices operating at LNT indicate the photogenerated carrier lifetime could be increased by the enhanced trapping–detrapping effect obviously, and the μτ product of CdSe SCs increases from 1.39 × 10−5 to 5.34 × 10−4 cm2 V−1 with temperature lowering from RT to LNT. Meanwhile, an ultrahigh sensitivity of 5.24 × 106μC Gyair−1 cm−2 and an extremely low detection limit of 3.68 nGyair s−1 have been acquired by the CdSe SC based x-ray detectors at LNT, which is 140 times higher and 5.8 times lower than it has been at RT. Compared with conventional semiconductor x-ray detectors, the ultra-high sensitivity and extremely low detection limit of CdSe SC based detectors make their application prospects very promising. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) perovskites have been demonstrated great promise in x-ray detection application because of their stability, tunability, and the unique electronic properties. The centimeter-sized 2D perovskite (PMA)2PbI4 single crystal and the corresponding x-ray detector were fabricated. The Cu ion implanted device exhibits an excellent sensitivity of 283 μC Gyair−1 cm−2, the significantly enhanced mobility-lifetime (μτ) product of 8.05 × 10−3 cm2 V−1, and the lowest detectable dose rate of 2.13 μGyair s−1. Experimental observation combined with the DFT calculations shows that the improvement in Cu ion implanted x-ray detection is ascribed to the enhanced photoinduced charge carrier density and μτ product, and the increased carrier dissociation capability associated deeply with the decreased binding energy of exciton in the inorganic layer quasi-quantum well. The incorporation of the Cu interstitials by high-energy Cu ion implantation is able to introduce the donor and acceptor states with additional charge transfer channeling, resulting in the decreased exciton binding energy and fast dissociation of the exciton and the quick carrier extraction. Cu ion implantation regulating the dissociation of charge carriers in low-dimensional perovskites will motivate the application for 2D perovskite in high-performance x-ray detectors. [ABSTRACT FROM AUTHOR]

Typical x-ray detectors have a fundamental trade-off between resolution and quantum efficiency (QE). High quantum efficiency x-ray detection requires a thick conversion medium, but decreases the resolution due to limited pixel aspect ratios for both direct and indirect x-ray detection. We present a method for x-ray detection, holographic x-ray detection, which uses photorefractive materials to create a high resolution and high efficiency detector. The x-ray image is recorded in the volume of the photorefractive material, bypassing the aspect ratio issue of typical x-ray detectors. Holographic x-ray detection operates in three stages: recording an x-ray hologram in a photorefractive crystal, reading the hologram with visible light, and then erasing the hologram using ultraviolet light. We have experimentally demonstrated holographic x-ray detection with a resolution of 208 lp/mm (80% QE at 40 keV), an order of magnitude resolution improvement over commercially available x-ray detectors while maintaining > 80% QE. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid perovskites have exhibited unprecedented advantages for x-ray photon detection due to their exotic properties. Their high-crystalline quality has a great impact for high-detection sensitivity under a low electric field, especially related to the synthesis method. In this work, we analyze the capability of CH3NH3PbI3 (MAPbI3) perovskites as an x-ray detection material and propose to control the temperature gradient (TG) during the synthesis of MAPbI3 single crystal perovskites for device fabrication. Our results show that the decreasing TG can effectively reduce the trap density and improve the crystal quality, which could lead to a boosted sensitivity of 1471.7 μC/Gyair/cm2 under a low electric field of 3.3 V/mm. In addition, a higher detection sensitivity can be achieved by increasing the electric field. Our work presents a strategy to construct high-performance direct x-ray detectors. [ABSTRACT FROM AUTHOR]

Thanks to their unique combination of semiconducting properties and a large cross section for energetic photons, metal halide perovskites could theoretically achieve high x-ray to charge carriers conversion rates, making them materials of high interest for the direct x-ray detection. In this work, we focus on the transport properties of methylammonium lead tribromide (MAPbBr3) single crystals. Time of Flight measurements and x-ray focused experiments along the edge of the samples were carried out. We report homogenous holes transit throughout the thickness of the samples as well as poor electrons transit. We also report the continuity of the electric field throughout the thickness of the MAPbBr3 samples, and we present preliminary fitting results to discuss its nature. [ABSTRACT FROM AUTHOR]

Metal halide perovskites (MHPs) changed the world of solution processed semiconductors, previously dominated by organic semiconductors, toward predominantly inorganic materials with a relatively high electron/hole mobility. A series of devices benefit from their optoelectronic properties, including X-ray detectors. After the introduction of MHP X-ray detectors in 2013, they have achieved significant improvements in the form of single crystals, polycrystalline materials, and pixelated imaging devices. In addition, MHPs in the form of colloidal nanocrystals act as excellent scintillators. We see the bright future of MHPs in energy resolved X-ray detection, either achieved in the single counting mode, or in nanocrystal multilayer stacked devices, acting as a combination of selective X-ray filters and scintillators. [ABSTRACT FROM AUTHOR]

This work is focused on a detailed study of pulsed mode infrared light induced depolarization of CdZnTe detectors operating at high photon fluxes. This depolarizing effect is a result of the decrease of positive space charge that is caused by the trapping of photogenerated holes at a deep level. The reduction in positive space charge is due to the optical transition of electrons from a valence band to the deep level due to additional infrared illumination. In this paper, we present the results of pulse mode infrared depolarization, by which it is possible to keep the detector in the depolarized state during its operation. The demonstrated mechanism represents a promising way to increase the charge collection efficiency of CdZnTe X-ray detectors operating at high photon fluxes. [ABSTRACT FROM AUTHOR]

Cadmium Zinc Telluride (CZT) is a wide band gap semiconductor for room temperature radiation detection. The electro-optic Pockels effect of the material has been exploited in the past to study electric field non-uniformities and their consequence on conventional detector signals in CZT, by imaging the intensity distribution of infrared (IR) light transmitted through a device placed between crossed polarizers. Recently, quantitative monitoring of extremely high intensity neutron pulses through the change of transmitted IR intensity was demonstrated, offering the advantage to place sensitive electronics outside the measured radiation field. In this work, we demonstrate that X-ray intensity can be deduced directly from measuring the change in phase of 1550 nm laser light transmitted through a 7 x 7 x 2 mm³ CZT based Pockels cell in a simple Mach Zehnder interferometer. X-rays produced by a 50 kVp Mo X-ray tube incident on the CZT cathode surface placed at 7 mm distance cause a linearly increasing phase shift above 0.3 mA tube current, with 1.58 60.02 rad per mA for an applied bias of 500 V across the 2 mm thick device. Pockels images confirm that the sample properties are in agreement with the literature, exhibiting electric field enhancement near the cathode under irradiation, which may cause the non-linearity at low X-ray tube anode current settings. The laser used to probe the X-ray intensity causes itself some space charge, whose spatial distribution does not seem to be exclusively determined by the incident laser position, i.e., charge carrier generation location, with respect to the electrodes. [ABSTRACT FROM AUTHOR]

Ring artifacts on tomogram slices hinder image interpretation. They are caused by minor variation in the response from individual elements in a two dimensional (2D) X-ray detector. Polar space decreases the suppression complexity by transforming the rings on the tomogram slice to linear stripes. However, it requires that the center of rings lie at the origin of polar transformation. If this is not the case, all methods employing polar space become ineffective. We developed a method based on Gaussian localization of the ring center in Hough parameter space to assign the origin for the polar transformation. Thus, obtained linear stripes can be effectively suppressed by already existing methods. This effectively suppresses ring artifacts in the data from a variety of experimental setups, sample types and also handles tomograms that are previously cropped. This approach functions automatically, avoids the need for assumptions and preserves fine details, all critical for synchrotron based nanometer resolution tomography. [ABSTRACT FROM AUTHOR]

The presence of Te inclusions is one of the main factors limiting performances of CdZnTe crystals as X-ray detectors. We show that by means of infrared laser radiation it is possible to move and anneal tellurium inclusions exploiting a thermo-diffusion mechanism. The process is studied live during irradiation by means of an optical microscope equipment. Experimental conditions, and, in particular, energy laser fluence, for annealing inclusions of different dimensions are determined. [ABSTRACT FROM AUTHOR]

With the aim of enhancing the efficiency with which plastic scintillators detect high-energy X-rays, hafnium-doped organic-inorganic hybrid scintillators were fabricated via a sol-gel method. Transmission electron microscopy of sampled material reveals the presence of HfxSi1-xO2 nanoparticles, dispersed in a polymer matrix that constitutes the active material of the X-ray detector. With HfxSi1-xO2 nanoparticles incorporated in the polymer matrix, the absorption edge and the luminescence wavelength is shifted, which we attribute to Mie scattering. The detection efficiency for 67.4-keV X-rays in a 0.6-mm-thick piece of this material is two times better than the same thickness of a commercial plastic scintillator-NE142. [ABSTRACT FROM AUTHOR]

Near edge responsivity in diamond x-ray detectors has been used to confirm the carrier loss mechanism as recombination due to diffusion into the incident electrode. We present a detailed study of the bias dependence of the diamond responsivity across the carbon k-edge. The carrier loss is modelled by incorporating a characteristic recombination length into the absorption model and is shown to agree well with Monte Carlo simulated carrier losses. Using the high sensitivity to the x-ray absorption depth, the responsivity is converted to a near edge x-ray absorption fine structure pattern allowing easy identification of absorption mechanisms. [ABSTRACT FROM AUTHOR]