Simulation and Experimental Validation of the Uniformity of Thermally Evaporated Amorphous Selenium Films for Large-Area Imaging and Radiation Detection Applications

Farahmandzadeh, Maryam; Marcinko, Steven; Jaramillo, Camilo; Cheng, Ming Kit; Curreli, Davide; Abbaszadeh, Shiva

doi:10.1109/ted.2020.3045963

Cited by 6 publications

(5 citation statements)

References 21 publications

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“…In all cases, substrates were cleaned by ultrasonication in acetone and isopropanol for 10 min each, rinsed with DI water, and dried with nitrogen. Films were deposited in a dedicated selenium evaporator capable of uniform layers covering areas up to 4 in., with a deposition rate of ∼100 Å/s and with the substrate at room temperature and rotated at 40 rpm . Pure selenium (Sigma-Aldrich, 99.999%), stabilized selenium (0.2% As, 10 ppm of Cl, Amalgamet), and 10% and 20% tellurium-doped selenium (Amalgamet) were combined to achieve intended concentrations of 0–15% Te atomic weight.…”

Section: Methodsmentioning

confidence: 99%

“…Hybrid functional approaches like HSE06 that express the exchange−correlation energy in terms of contributions from density functional theory and Hartree−Fock exact exchange have been shown to provide reasonable estimates for the experimental band gap of many materials. 45 For band gap predictions, we have taken the structures relaxed using density functional theory with the PBE functional and performed additional calculations using the HSE06 hybrid functional. The electronic structure of amorphous materials differs greatly from crystalline materials due to the loss of symmetry.…”

Section: Methodsmentioning

confidence: 99%

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Tuning Amorphous Selenium Composition with Tellurium to Improve Quantum Efficiency at Long Wavelengths and High Applied Fields

Hellier

Stewart

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et al. 2023

ACS Appl. Electron. Mater.

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Amorphous selenium (a-Se) is a large-area compatible photoconductor that has received significant attention toward the development of UV and X-ray detectors for a wide range of applications in medical imaging, life science, high-energy physics, and nuclear radiation detection. A subset of applications require detection of photons with spectral coverage from UV to infrared wavelengths. In this work, we present a systematic study utilizing density functional theory simulations and experimental studies to investigate optical and electrical properties of a-Se alloyed with tellurium (Te). We report hole and electron mobilities and conversion efficiencies for a-Se1–x Te x (x = 0, 0.03, 0.05, 0.08) devices as a function of applied field, along with band gaps and comparisons to previous studies. For the first time, these values are reported at high electric field (>10 V/μm), demonstrating recovery of quantum efficiency in Se–Te alloys. A comparison to the Onsager model for a-Se demonstrates the strong field dependence in the thermalization length and expands on the role of defect states in device performance.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Tuning Amorphous Selenium Composition with Tellurium to Improve Quantum Efficiency at Long Wavelengths and High Applied Fields

Hellier

Stewart

Read

et al. 2023

ACS Appl. Electron. Mater.

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“…This device, as will be shown in this paper, represents a low cost, simple to manufacture, and scalable solution to a large area VUV sensitive photosensor. The PCB manufacturing process for areas as large as 2000 cm 2 is commercially ready and low cost [45], the process of uniform and repeatable thermal evaporation techniques over these areas is well demonstrated [46], and the ability to scale together large area tiles into one uniform collection plane is commonly done in experiments [47,48]. Moreover, the ability for the device to respond to VUV light using this windowless approach simplifies the characterization and testing of the device.…”

Section: Amorphous Selenium Boardsmentioning

confidence: 99%

Development of a novel, windowless, amorphous selenium based photodetector for use in liquid noble detectors

et al. 2023

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Detection of the vacuum ultraviolet (VUV) scintillation light produced by liquid noble elements is a central challenge in order to fully exploit the available timing, topological, and calorimetric information in detectors leveraging these media. In this paper, we characterize a novel, windowless amorphous selenium based photodetector with direct sensitivity to VUV light. We present here the manufacturing and experimental setup used to operate this detector at low transport electric fields (2.7–5.2 V/μm) and across a wide range of temperatures (77 K–290 K). This work shows that the first proof-of-principle windowless amorphous selenium device is robust under cryogenic conditions, responsive to VUV light at cryogenic temperatures, and preserves argon purity. These findings motivate a continued exploration of amorphous selenium devices for simultaneous detection of scintillation light and ionization charge in noble element detectors.

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“…For the samples with a blocking layer, a diluted PI layer (2 g of HDMS PI-2610 to 1 mL N-methyl-2-pyrrolidone) was spun at 500 r/min for 5 s, then 1450 r/min for 60 s, dried at 90 • C for 120 s, then ramped to 350 • C at 4 • /min to hard bake for 30 min, and finally allowed to gradually cool to room temperature on the now-off hotplate. Stabilized selenium (0.2% As, 10 ppm Cl-Amalgamet) was deposited via thermal evaporation in a dedicated selenium evaporator at 100 Å/s while rotating at 40 r/min; further details of the system may be found in [45]. Gold electrodes with 3, 4, and 5 mm diameters were deposited by electron beam evaporation at 1 Å/s.…”

Section: A Device Fabricationmentioning

confidence: 99%

Performance Evaluation of an Amorphous Selenium Photodetector at High Fields for Application Integration

et al. 2023

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Polyimide (PI) has been utilized as a hole-blocking layer (HBL) in high-resistivity photoconductors such as amorphous selenium (a-Se) and amorphous lead oxide (a-PbO). It prevents hole injection from the positively biased electrode and suppresses the dark current of the detector. To determine the performance parameters of an a-Se/PI detector for readout design and specification for different radiation detection applications, knowledge of the accurate voltage drop within the photoconductor is crucial. Here, we precisely determine the voltage drop across a-Se when interfaced with a thin layer of PI (1 µm) and characterize its temporal resolution (rise time and jitter), dynamic range, and quantum efficiency (QE) as a function of the electric field. The photoresponse of the detector is characterized using light-emitting diodes in the ultraviolet (UV, 355-400-nm wavelength) and visible (400-533-nm wavelength) regions of the light spectrum. We find the voltage drop across a-Se as 91% of the total applied voltage. This results in a QE near unity at 405 nm for corrected fields beginning at 45 V/µm. At fields of 50 V/µm, we observe rise times of 3.7 ns and jitter of 130 ps.

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Simulation and Experimental Validation of the Uniformity of Thermally Evaporated Amorphous Selenium Films for Large-Area Imaging and Radiation Detection Applications

Cited by 6 publications

References 21 publications

Tuning Amorphous Selenium Composition with Tellurium to Improve Quantum Efficiency at Long Wavelengths and High Applied Fields

Tuning Amorphous Selenium Composition with Tellurium to Improve Quantum Efficiency at Long Wavelengths and High Applied Fields

Development of a novel, windowless, amorphous selenium based photodetector for use in liquid noble detectors

Performance Evaluation of an Amorphous Selenium Photodetector at High Fields for Application Integration

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