Bilayer lead oxide X-ray photoconductor for lag-free operation

AbstractPolycrystalline Lead Oxide (poly-PbO) was considered one of the most promising photoconductors for the direct conversion X-ray medical imaging detectors due to its previous success in optical imaging, i.e., as an optical target in so-called Plumbicon video pick-up tubes. However, a signal lag which accompanies X-ray excitation, makes poly-PbO inapplicable as an X-ray-to-charge transducer in real-time X-ray imaging. In contrast, the recently synthesized Amorphous Lead Oxide (a-PbO) photoconductor is essentially lag-free. Here, we report on our approach to a PbO detector where a thin layer of a-PbO is combined with a thick layer of poly-PbO for lag-free operation. In the presented a-PbO/poly-PbO bilayer structure, the poly-PbO layer serves as an X-ray-to-charge transducer while the a-PbO acts as a lag prevention layer. The hole mobility in the a-PbO/poly-PbO bilayer structure was measured by photo-Charge Extraction by Linearly Increasing Voltage technique at different temperatures and electric fields to investigate charge transport properties. It was found that the hole mobility is similar to that in a-Se—currently the only commercially viable photoconductor for the direct conversion X-ray detectors. Evaluation of the X-ray temporal performance demonstrated complete suppression of signal lag, allowing operation of the a-PbO/poly-PbO detector in real-time imaging.

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The X-ray Sensitivity of an Amorphous Lead Oxide Photoconductor

Sensors ◽

10.3390/s21217321 ◽

2021 ◽

Vol 21 (21) ◽

pp. 7321

Author(s):

Oleksandr Grynko ◽

Tristen Thibault ◽

Emma Pineau ◽

Alla Reznik

Keyword(s):

Electric Fields ◽

Lead Oxide ◽

Direct Conversion ◽

Amorphous Selenium ◽

X Rays ◽

X Ray ◽

Optimal Detector ◽

Imaging Detector ◽

Electron Hole Pair ◽

Underlying Mechanisms

The photoconductor layer is an important component of direct conversion flat panel X-ray imagers (FPXI); thus, it should be carefully selected to meet the requirements for the X-ray imaging detector, and its properties should be clearly understood to develop the most optimal detector design. Currently, amorphous selenium (a-Se) is the only photoconductor utilized in commercial direct conversion FPXIs for low-energy mammographic imaging, but it is not practically feasible for higher-energy diagnostic imaging. Amorphous lead oxide (a-PbO) photoconductor is considered as a replacement to a-Se in radiography, fluoroscopy, and tomosynthesis applications. In this work, we investigated the X-ray sensitivity of a-PbO, one of the most important parameters for X-ray photoconductors, and examined the underlying mechanisms responsible for charge generation and recombination. The X-ray sensitivity in terms of electron–hole pair creation energy, W±, was measured in a range of electric fields, X-ray energies, and exposure levels. W± decreases with the electric field and X-ray energy, saturating at 18–31 eV/ehp, depending on the energy of X-rays, but increases with the exposure rate. The peculiar dependencies of W± on these parameters lead to a conclusion that, at electric fields relevant to detector operation (~10 V/μm), the columnar recombination and the bulk recombination mechanisms interplay in the a-PbO photoconductor.

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Analysis of lead oxide (PbO) layers for direct conversion X-ray detection

IEEE Transactions on Nuclear Science ◽

10.1109/tns.2005.856790 ◽

2005 ◽

Vol 52 (5) ◽

pp. 2035-2040 ◽

Cited By ~ 46

Author(s):

M. Simon ◽

R.A. Ford ◽

A.R. Franklin ◽

S.P. Grabowski ◽

B. Menser ◽

...

Keyword(s):

Lead Oxide ◽

Direct Conversion ◽

X Ray

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Analysis of lead oxide (PbO) layers for direct conversion X-ray detection

IEEE Symposium Conference Record Nuclear Science 2004. ◽

10.1109/nssmic.2004.1466833 ◽

2005 ◽

Cited By ~ 5

Author(s):

M. Simon ◽

R.A. Ford ◽

A.R. Franklin ◽

S.P. Grabowski ◽

B. Menser ◽

...

Keyword(s):

Lead Oxide ◽

Direct Conversion ◽

X Ray

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Morphology, Opto-Electronic and Dielectric Properties of Vacuum Sublimed CuPc Based Thin Films

Journal of Nanoelectronics and Optoelectronics ◽

10.1166/jno.2019.2654 ◽

2019 ◽

Vol 14 (11) ◽

pp. 1523-1531

Author(s):

Manjit Kaur ◽

Rakesh Dogra ◽

Narinder Arora ◽

Navjeet Sharma ◽

Rajesh Kumar

Keyword(s):

Thin Films ◽

Hole Mobility ◽

X Ray Diffraction ◽

Visible Absorption ◽

X Ray ◽

Optical Band Gaps ◽

Different Temperatures ◽

Evaporation Technique ◽

Uv Visible ◽

Substrate Temperatures

AC transport properties and dielectric response of sandwich geometry (Ag/CuPc/Ag) of CuPc(CuPc) thin films deposited using thermal evaporation technique have been studied within frequency range 1 Hz–10 KHz and in temperature range 303–383 K. Scanning electron microscope (SEM) investigations of these films reveal fiber like morphology. Crystalline natures of CuPc films have been characterized using X-ray diffraction for different temperatures. The molecular orientations in films for different substrate temperatures have been confirmed by Raman spectroscopy. The optical band gaps calculated from the UV–Visible absorption spectra is found to lie in the range 3.01–3.15 eV. Electrical conductivity of CuPc films increases with increase of temperature. The hole mobility values of CuPc films at different temperatures have been calculated using negative differential susceptance (–ΔB) technique. Both capacitance and dielectric constant have been found to decrease with the increase of frequency and temperature.

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Examples of Hydrothermal Titration and Real Time X-Ray Diffraction in the Synthesis of Open Frameworks

MRS Proceedings ◽

10.1557/proc-453-103 ◽

1996 ◽

Vol 453 ◽

Cited By ~ 3

Author(s):

J. B. Parise ◽

K. Tan ◽

P. Norby ◽

Y. Ko ◽

C. Cahill

Keyword(s):

Real Time ◽

Ammonium Hydroxide ◽

Continuous Exposure ◽

X Ray Diffraction ◽

X Ray ◽

Synthetic Strategy ◽

X Ray Scattering ◽

Different Temperatures ◽

Imaging Plates ◽

Insight Into

AbstractHydrothermal titration (HTT) techniques represent a new synthetic strategy for the production of open frameworks. As an example, initial digestion of amorphous GeS2 in the presence of tetraethyl ammonium hydroxide (TEAOH) at 100°C is followed by injection of Ag+ into this mixture to condense the [Ge4S10]4− clusters and form a framework consisting of 8-ring channels bounded by alternating GeS-clusters and Ag+. The rational use of this apparatus depends upon determining the timing of injection. Insight into the changes occurring during reactant digestion is provided by real time synchrotron X-ray powder diffraction. Changes in the the system dimethylamine-Sb-S have been followed in real time at different temperatures. The transformation from mixtures of DMA, Sb and S to the known open phase DMA-SbS-SB8 was followed by observing monochromatic X-ray scattering detected on an imaging plates over a 8 hr period with one continuous exposure.

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Characterization of polycrystalline lead oxide for application in direct conversion X-ray detectors

Scientific Reports ◽

10.1038/s41598-017-09168-3 ◽

2017 ◽

Vol 7 (1) ◽

Cited By ~ 14

Author(s):

O. Semeniuk ◽

O. Grynko ◽

G. Decrescenzo ◽

G. Juska ◽

K. Wang ◽

...

Keyword(s):

Lead Oxide ◽

Direct Conversion ◽

X Ray

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Current Status of Solid-State X-Ray Systems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117789 ◽

1985 ◽

Vol 43 ◽

pp. 158-161

Author(s):

Martin Peckerar ◽

Anastasios Tousimis

Keyword(s):

Solid State ◽

Electric Fields ◽

Spectral Lines ◽

Current Status ◽

Mobile Charge ◽

Electron Hole ◽

X Ray ◽

Sensing Systems ◽

Transmission Electron ◽

Electron Microscopes

Solid state x-ray sensing systems have been used for many years in conjunction with scanning and transmission electron microscopes. Such systems conveniently provide users with elemental area maps and quantitative chemical analyses of samples. Improvements on these tools are currently sought in the following areas: sensitivity at longer and shorter x-ray wavelengths and minimization of noise-broadening of spectral lines. In this paper, we review basic limitations and recent advances in each of these areas. Throughout the review, we emphasize the systems nature of the problem. That is. limitations exist not only in the sensor elements but also in the preamplifier/amplifier chain and in the interfaces between these components.Solid state x-ray sensors usually function by way of incident photons creating electron-hole pairs in semiconductor material. This radiation-produced mobile charge is swept into external circuitry by electric fields in the semiconductor bulk.

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