Sensitive direct-conversion X-ray detectors formed by ZnO nanowire field emitters and β-Ga2O3 photoconductor targets with an electron bombardment induced photoconductivity mechanism

Zhipeng Zhang; Manni Chen; Xinpeng Bai; Kai Wang; Huanjun Chen; Shaozhi Deng; Jun Chen

doi:10.1364/PRJ.438204

Journals >Photonics Research >Volume 9 >Issue 12 >Page 2420 > Article

Photonics Research
Vol. 9, Issue 12, 2420 (2021)

Sensitive direct-conversion X-ray detectors formed by ZnO nanowire field emitters and β-Ga₂O₃ photoconductor targets with an electron bombardment induced photoconductivity mechanism

Zhipeng Zhang, Manni Chen, Xinpeng Bai, Kai Wang, Huanjun Chen, Shaozhi Deng, and Jun Chen^*

Author Affiliations

State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China

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DOI: 10.1364/PRJ.438204 Cite this Article Set citation alerts

Zhipeng Zhang, Manni Chen, Xinpeng Bai, Kai Wang, Huanjun Chen, Shaozhi Deng, Jun Chen. Sensitive direct-conversion X-ray detectors formed by ZnO nanowire field emitters and β-Ga₂O₃ photoconductor targets with an electron bombardment induced photoconductivity mechanism[J]. Photonics Research, 2021, 9(12): 2420 Copy Citation Text

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Comparison of conceptual design of X-ray detectors and corresponding X-ray response mechanism. (a) Conventional X-ray detectors with TFT readout. (b) Proposed X-ray detectors with vacuum FEA readout.

Fig. 1. Comparison of conceptual design of X-ray detectors and corresponding X-ray response mechanism. (a) Conventional X-ray detectors with TFT readout. (b) Proposed X-ray detectors with vacuum FEA readout.

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Implementation and characterizations of the X-ray detectors. (a) Schematic layout of the vacuum cold cathode X-ray detector. (b) Actual picture of the fabricated X-ray detector. (c) Arrays of patterned ZnO NWs (top image) and cross-sectional view of ZnO NWs (bottom image). (d) Field emission J-E curve of the ZnO NWs with inset showing the corresponding F-N curve. (e) Typical XRD pattern of β-Ga2O3 bulk photoconductor. (f) Total mass attenuation of X-rays in β-Ga2O3 bulk photoconductor showing the contribution from Compton scattering, photoelectric effect, and pair production and that of a-Se and CsPbBr3 photoconductors.

Fig. 2. Implementation and characterizations of the X-ray detectors. (a) Schematic layout of the vacuum cold cathode X-ray detector. (b) Actual picture of the fabricated X-ray detector. (c) Arrays of patterned ZnO NWs (top image) and cross-sectional view of ZnO NWs (bottom image). (d) Field emission J-E curve of the ZnO NWs with inset showing the corresponding F-N curve. (e) Typical XRD pattern of β-Ga2O3 bulk photoconductor. (f) Total mass attenuation of X-rays in β-Ga2O3 bulk photoconductor showing the contribution from Compton scattering, photoelectric effect, and pair production and that of a-Se and CsPbBr3 photoconductors.

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Fig. 3. Detection performance and operation principle of the proposed X-ray detector. (a), (b) Dark current and photocurrent of the X-ray detector at low and high electric fields. (c) F-N curves of the dark current and photocurrent. (d)–(f) Schematic of the operation principle of X-ray detector at different applied electric fields. (g) The detection sensitivity versus applied electric field curves of the X-ray detector. (h) Internal gain versus electric field curve of the detector under X-ray illumination with the X-ray tube voltage of 6 kV and the X-ray tube current of 0.6 mA. (i) The detection sensitivity versus X-ray tube voltage curves of the X-ray detector with inset showing the theoretical determination of detector sensitivity as a function of X-ray energy. (The experimental value was measured using a DC X-ray tube without beam filters.)

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Fig. 4. Temporal response of the X-ray detector. (a)–(c) Time-dependent photocurrent of the X-ray detector with pulsed X-ray source on and off at 5 V μm-1 electric field. (d) The SNRs under different X-ray dose rates with inset showing the temporal responses under different X-ray dose rates.

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X-ray Detector Type	Photomultiplier Mechanism	Linear Attenuation Coefficient (for 20 keV X-ray, ${mm}^{- 1}$ )	X-ray Energy Range (keV)	Operating Electric Field ( $V {μm}^{- 1}$ )	Dark Current ( $pA {mm}^{- 2}$ )	Photocurrent ( $pA {mm}^{- 2}$ , @X-ray energy, X-ray dose, thickness)	Sensitivity ( ${μCGy}_{air}^{- 1} {cm}^{- 2}$ )	Internal Gain	Response Time (ms)	Detection Limit ( ${mGy}_{air} s^{- 1}$ )	Reference
${Ga}_{2} O_{3}$ driven by cold cathode	EBIPC	17.2	6–50	22.5	$1.6 \times 10^{5}$	$1.8 \times 10^{5}$ (50 keV, $22.8 {mGy}_{air} s^{- 1}$ , 0.68 mm)	$3.0 \times 10^{3}$	$2.9 \times 10^{2}$	40	0.28	This work
${Ga}_{2} O_{3}$	None	17.2	30–60	0.025	$4.0 \times 10^{6}$	$1.8 \times 10^{7}$ (24 keV, $383 {mGy}_{air} s^{- 1}$ , 1 mm)	$\sim 1.4 \times 10^{3}$	None	$1.4 \times 10^{3}$	$\sim 3.8 \times 10^{2}$	[40]
a-Se driven by cold cathode	Avalanche effect	22.8	20–40	100	$\sim 9.0$	$\sim 90$ (80 keV, $1.8 {nGy}_{air} s^{- 1}$ , 15 μm)	Unknown	$2.0 \times 10^{2}$	$\sim 33$	Unknown	[41,42]
a-Se	None	22.8	20–60	10	$\sim 10$	$\sim 10^{3}$ (20 keV, unknown, 200 μm)	22.5	None	$< 33$	$5.5 \times 10^{- 3}$	[11,43,44]
Perovskite ( ${CsPbBr}_{3}$ )	Photoconductive gain effect	26.2	30–50	0.01	$\sim 2.0 \times 10^{4}$	$\sim 8.0 \times 10^{4}$ (30 keV, $140 {μGy}_{air} s^{- 1}$ , 240 μm)	$5.6 \times 10^{4}$	$\sim 9.0 \times 10^{3}$	92	$2.2 \times 10^{- 4}$	[6]
Perovskite ( ${CsPbBr}_{3}$ )	None	26.2	20–60	0.005	$\sim 10$	$\sim 500$ (60 keV, $20 {μGy}_{air} s^{- 1}$ , 1 mm)	$4.1 \times 10^{3}$	None	$< 0.3$	$< 2.2 \times 10^{- 4}$	[45]

Table 1. Comparison of Performance Metrics of Direct-Conversion X-ray Detectors Based on Different Photoconductors and Photoelectron Multiplication Mechanisms