1 CMOS based high -resolution dynamic X -ray imaging with inorganic perovskite

2025-04-28 0 0 927.87KB 18 页 10玖币

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CMOS based high-resolution dynamic X-ray imaging

with inorganic perovskite

Yanliang Liua, Chaosong Gaob, Jiongtao Zhua, Xin Zhanga, Meng Wub, Ting Sua, Jiahong Wanga, Zonghai

Shenga, Wenjun Liua, Tongyu Shia, Xingchen Hea, Dong Lianga, Hairong Zhenga, Xue-Feng Yua,

Xiangming Sunb, Yongshuai Gea

aShenzhen Institute of Advanced Technology, Chinese Academy of Sciences, China

bCentral China Normal University, Wuhan, Hubei, China

Y.Liu and C.Gao made equal contribution to this work.

Email: xf.yu@siat.ac.cn, xmsun@phy.ccnu.edu.cn, ys.ge@siat.ac.cn

Abstract: High-resolution dynamic X-ray detector is crucial for time-resolved digital radiography

(DR) imaging and fast 3D medical computed tomography (CT) imaging. Recently, perovskites

have become promising alternatives to conventional semi-conductor materials, e.g., Si, a-Se

and CdTe, for direct X-ray detection. However, the feasibility of their combination with high-

speed pixelated complementary metal-oxide-semi- conductor (CMOS) arrays remains unknown.

This work originally reports an innovative direct-conversion X-ray detector fabricated with 300

micrometer thick inorganic perovskite film printed on a tailored CMOS array. In-house

measurements demonstrate that the CsPbBr3 film has excellent optoelectric properties of a μτ

product of 3.40×10-5 cm2 V–1, and the X-ray detector exhibits high sensitivity of 9341 µC Gyair–1

cm–2, and low detection limit of 588 nGyair s–1. This CMOS X-ray imaging detector achieves a

high spatial resolution up to 5.5 lp/mm (close to the resolution limit of 6.0 lp/mm), and >300 frame

per second (fps) readout speed. DR image of a resolution pattern phantom and a anesthesia

mice, CT images of a biological specimen are acquired for the first time.

 
2 
 
Since its discorvery in 1895, X-ray imaging has shown superb performance in unveiling the 
anatomical sturctures of the human body. By far, X-ray imaging has been widely used in many 
medical  applications,  such  as  the  diagnosis  and  treatment  of  cardiovascular  and  cancer 
diseases1,2.  In  order  to  generate  sufficient  X-ray  imaging  information  for  clinicians  to  make 
precise diagnoses, usually, X-ray detectors with unique features such as high spatial resolution, 
fast  imaging speed are highly demanded. In addition, to minimize its cancerous damage to 
human body, its low dose X-ray imaging performance is also an important factor to be considered 
to use as low as reasonably achievable (ALARA) radiation dose3. 
Over the past two decades, dedicated academic and clinical investigations have been performed 
to develop the most appropriate X-ray detectors for ultra-high quality medical imaging. Results 
demonstrate the direct-conversion type X-ray detectors made of semi-conductor materials show 
better spatial and temporal resolution at low radiation dose  X-ray imaging than the indirect-
conversion ones made of scintillator materials4. However, the current semi-conductor materials 
used in commercial direct-conversion type X-ray detectors are less satisfactory for generic X-
ray imaging purposes. For example, the amorphous selenium (a-Se)5,6 only works at low energy 
X-ray photons (<40 keV) due to its low stopping power (Z=34), which are merely restricted for 
breast imaging. Moreover, the cadmium zinc telluride (CdZnTe)7 or cadmium telluride (CdTe) 
crystals have shown its advancements in fabricating high-energy (>140 keV) X-ray detectors 
with energy-resolving capability. However, the CdZnTe/CdTe are are difficult to grow into large 
dimensions, and thus are hard to be used for large area X-ray imaging. The high cost also 
prohibits their wide spreads in medical X-ray imaging applications. In addition, the requirement 
of flip chip assembly using Indium solder bumps to interconnect the CdZnTe/CdTe crystal slab 
to the back-end ASIC readout circuit complicates the detector fabrication as well. 
As an emerging candidate, metal halide perovskites8,9,10,11, e.g., single crystal, polycrystalline 
wafer  and  solvent-processed  thick  film,  show  excellent  potentials  in  realizing  high-sensitive 

 
3 
 
(≥50000 µC Gyair-1cm-2) direct X-ray detection, such as high X-ray absorption, high charge carrier 
mobility (μ) and long carrier lifetime (τ). By integrating with pixelated sensor arrays, prototypes 
of perovskite-based X-ray imaging detectors have been successfully fabricated. In 2017, Park 
et.al. first reported the promise of high-resolution X-ray imaging with blade-coating CH3NH3PbI3 
films on a large-scale thin-film transistor (TFT) backplane12. In 2021, Sarah et.al. reported a two-
step  procedure  to  manufacture  X-ray  detector  with  microcrystalline  CH3NH3PbI3  on  TFT 
backplane13. Recently, Tang et.al. fabricated a flat-panel X-ray imager by combination of soft-
presssing CH3NH3PbI3 films and TFT backplane14. 
Technically,  the  direct-conversion  perovksite  X-ray detectors  having  the most  ideal  imaging 
performance  should  be  fabricated  upon  the  Complementary  Metal-Oxide-Semiconductor 
(CMOS) sensors15, which have become the majority of consumer and prosumer cameras these 
days due to their much more distinct advantages16,17,18 in achieving ultra-high image resolution 
and data readout speed19. For example, the pixel size of CMOS sensor can be easily made 
smaller  than  5  micrometers,  whereas,  the  pixel  size  of  TFT  array  is  usually  larger  than  70 
micrometers. Besides, the CMOS sensor also has stronger noise immunity and lower static 
power utilization. As a consequence, CMOS sensor arrays should be selected to completely 
fulfill the advancements of perovksites in achieving high-end direct-conversion X-ray imaging 
with unprecedented spatial and temporal resolution. Moreover, special electrical circuits can be 
designed and integrated into the CMOS pixel unit to surpress the leakage dark current of the 
perovksites20,  which  is still  a  remaining  issue  in  developing  X-ray  imaging  detector array21. 
Unfortunately,  by  far  no  such  studies  have  been  demonstrated  on  a  CMOS  sensor  based 
perovskite X-ray detector. 
In  this  work,  we  report  an  innovative  direct-conversion  X-ray  detector  fabricated  with  300 
micrometer thick inorganic CsPbBr3 perovskite film printed on a tailored CMOS sensor array22,23. 
The main structure of the X-ray imager was illustrated in Fig. 1a. As shown, certain electric field 

is applied to propel the X-ray photon stimulated electrons within the perovskite to drift towards

the signal collection electrode, namely, the CMOS pixel. The perovskite film covered CMOS

device with total number of 72×72 pixels is depicted in Fig. 1b. The perovskite film was printed

directly on the CMOS chip via the silk-screen priting process. The cross-section SEM image

shows that such in-situ grown CsPbBr3 film has good affinity with the CMOS array, in which

multi-layered parasitic capacitance with multifunctional complex circuits of amplifier and leakage

current compensation are integrated to enhance high SNR signal detections. The detector could

endure more than four months without significantly degrading its X-ray imaging performance,

indicating a excellent working stability of CsPbBr3 film under X-ray exposure and high electric

field conditions. This CMOS based direct-conversion X-ray detector can resolve objects with a

very fine structure of 5.5 lp/mm, see Fig. 1c. It was obtained at a bias voltage of 15V,

corresponding to an electric field of 0.05 V/um inside the perovskite film. This experiment was

validated by a bar pattern plate having 33 groups of different Pb lines with varied widths and

spacing distances. Since the limit spatial resolution of this CMOS array is found to be 6.0 lp/mm

(corresponds to the 83.2 μm pitch dimension), therefore, this X-ray detector shows an

unprecedented high-resolution imaging performance. For this special CMOS array, the gate

voltage of the feedback transistor, denoted as V, controls the decay time of the Charge Sensitive

Amplifier (CSA) for every single pixel (see Methods for details). To inhibit the pixel-by-pixel varied

leakage current, especially to avoid the signal saturations, the gate voltage was adjusted

according to the amplitude of the leakage current without turning on the X-ray beam. The 3D

distribution map of the pixel response is illustrated in Fig. 1d. In general, the pixel response

decreases as the used gate voltage increases. To suppress the internal dark current of the

perovskite film, certain gate voltages are calibrated and adopted before X-ray exposures. For

larger dark current signals, higher gate voltages are needed to maintain similar pixel responses.

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1CMOSbasedhigh-resolutiondynamicX-rayimagingwithinorganicperovskiteYanliangLiua,ChaosongGaob,JiongtaoZhua,XinZhanga,MengWub,TingSua,JiahongWanga,ZonghaiShenga,WenjunLiua,TongyuShia,XingchenHea,DongLianga,HairongZhenga,Xue-FengYua,XiangmingSunb,YongshuaiGeaaShenzhenInstituteofAdvancedTechnology,Chine...

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1 CMOS based high -resolution dynamic X -ray imaging with inorganic perovskite

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