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Halide perovskites have demonstrated great potential in x-ray detectors, due to their high x-ray attenuation coefficient, large bulk resistance, ultralong carrier diffusion length, and adjustable bandgap. Moreover, their abundant raw materials and simple processing combined with excellent compatibility with integrated circuits make them ideal for cost-efficient and high-efficiency real-world imaging applications. Herein, we comprehensively reviewed advances and progress in x-ray detection devices based on halide perovskites. We expound on the fundamental mechanisms of interactions between x rays and matter as background and indicate different parameters for different types of x-ray detectors, which guides the basic requirements on how to select and design suitable materials for active layers. After emphasizing the superb properties of halide perovskites through the shortcomings of commercial materials, we evaluate the latest advancements and ongoing progress in halide perovskites with different dimensions and structures for both direct and indirect x-ray detectors, and discuss the effect of dimensional varieties on the device performance. We also highlight current challenges in the area of perovskite x-ray detectors and propose corresponding solutions to optimize halide perovskites and optimize x-ray detectors for next-generation imaging applications. [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]

Solution grown metal halide perovskites (MHPs) are a class of low-cost, direct conversion semiconducting materials with the potential to meet the need for large areas, high stopping power, and high sensitivity x-ray detectors. While polycrystalline MHP thin films have shown significant potential for meeting this need, their efficiencies for detecting x rays are limited by their thickness. This article presents an MHP variant, methylammonium lead tribromide (MAPB) in the form of 3D polycrystalline mosaic wafers with relatively high hole transport properties that demonstrated stable sensitivity during irradiation. An expedited and efficient detector fabrication method that did not include polishing or sintering was evaluated, and a radiograph of a brass key was produced using electron collection from the resulting wafer. However, a high dose rate was required due to very low sensitivity values. The effects of surface inhomogeneity and radiation damage were investigated as explanatory factors, and these phenomena were further characterized through IV measurements, current response as a function of electric field and x-ray dose rate, and alpha particle irradiation. The results indicated that although compromising surface quality for fabrication efficiency was the primary hindrance to the x-ray detection performance of 3D polycrystalline MAPB, stable performance could still be achieved under reasonable dose rates. [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]

Two-dimensional transition metal dichalcogenides (TMDCs) are demonstrated to be appealing semiconductors for optoelectronic applications, thanks to their remarkable properties in the ultraviolet-visible spectral range. Interestingly, TMDCs have not yet been characterized when exposed to x rays, although they would be ideal candidates for optoelectronic applications in this spectral range. They benefit from the high cross section of the constituent heavy atoms, while keeping the absorption very low, due to the ultrathin structure of the film. This encourages the development of photodetectors based on TMDCs for several applications dealing with x rays, such as radioprotection, medical treatments, and diagnosis. Given the atomic thickness of TMDCs, they can be expected to perform well at low dose measurements with minimal perturbation of the radiation beam, which is required for in vivo applications. In this paper, the use of TMDCs as active materials for direct x-ray detection is demonstrated, using a photodetector based on a MoS2 monolayer (1L-MoS2). The detector shows a response to x rays in the range of 101–102 keV, at dose rates as low as fractions of mGy/s. The sensitivity of 1L-MoS2 reaches values in the range of 108–109µC Gy−1 cm−3, overcoming the values reported for most of the organic and inorganic materials. To improve the x-ray photoresponse even further, the 1L-MoS2 was coupled with a polymeric film integrating a scintillator based on terbium-doped gadolinium oxysulfide (Gd2O2S:Tb). The resulting signal was three times larger, enabled by the indirect x ray to visible photoconversion mechanism. This paper might pave the way toward the production of ultrathin real-time dosimeters for in vivo applications. [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]

This paper describes the development of a novel medical x-ray imaging system adapted to the needs and constraints of low- and middle-income countries. The developed system is based on an indirect conversion chain: a scintillator plate produces visible light when excited by the x rays, and then, a calibrated multi-camera architecture converts the visible light from the scintillator into a set of digital images. The partial images are then unwarped, enhanced, and stitched through parallel field programmable gate array processing units and specialized software. All the detector components were carefully selected focusing on optimizing the system's image quality, robustness, cost-effectiveness, and capability to work in harsh tropical environments. With this aim, different customized and commercial components were characterized. The resulting detector can generate high quality medical diagnostic images with detective quantum efficiency levels up to 60% (@2.34 μGy), even under harsh environments, i.e., 60 °C and 98% humidity. [ABSTRACT FROM AUTHOR]

In this work, a large size x-ray detector with a 25 mm2 active area is demonstrated based on a thick 4H-SiC p-i-n structure. The detector exhibits obvious merits of high photon sensitivity over 4 × 104μC Gy−1 cm−2, good photon-response linearity, and high-temperature operation compatibility. Meanwhile, due to the ultralow leakage current level achieved, single photon detection performance for x-ray photons is further realized with energy resolutions of 1.1 and 4.9 keV at 5.9 and 59.5 keV, respectively. This work thus suggests the significant potentials of wide-bandgap SiC semiconductor for photon-resolved x-ray detection in a harsh environment. [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]

Large-grain-sized polycrystalline diamond films are fabricated by electron assisted chemical vapor deposition. A pure SP3 carbon bond in the cubic lattice structure is confirmed by Raman spectrum analysis. The grain size is on the order of several hundreds of μm or larger. Interlaced-finger electrodes are imprinted onto a 6 × 6 mm2 × 500 µm film to fabricate the x-ray detector. The width of every finger is 25 µm, and the distance between nearby fingers is 25 μm. Strong x ray irradiates when a pulsed current flows through a double-layer nested tungsten wire array in the Z-pinch. This diamond detector now works as one of the main x-ray detectors for the Z-pinch device. The diamond detector is calibrated using a plastic scintillator. The comparison between the signal measured by these two methods confirms that the large-grain-sized polycrystalline diamond is a good candidate for the detection of nanosecond pulsed x ray. [ABSTRACT FROM AUTHOR]

X-ray communication (XCOM) offers important advantages to both civilian and military space projects. Rapid advance in high-intensity laser interaction with plasma has become a driving force for providing a new X-ray carrier generation based on the laser wakefield acceleration scheme. XCOM has the potential to eliminate RF shielding on the ground and communicate with the re-entry supersonic spacecraft during blackout occurrence. In this process, the plasma sheath is formed around the surface due to air compression and ablation, which blocks the traditional communication signals. In this paper, the hazardous substance was proactively exploited and coupled with the modulated laser. Particle-In-Cell simulation results indicate the ultra-bright controllable X-ray emission with a small angular divergence (0.04 rad × 0.03 rad), a tunable X-ray energy range (4.60 keV to 321.48 keV), and high photon yields. Additionally, the data rate of the communication via the X-ray carrier during re-entry was estimated up to ∼20.7 Mbps by considering the transmission model, encoding schemes and photon information efficiency. Combined with an existing or developing X-ray detection technique, this regime can eliminate re-entry blackout and also provide a novel modulated X-ray source to acquire high-rate, low transmit power, and highly secure space-based data links. [ABSTRACT FROM AUTHOR]