Microstructured Neutron Detectors Research Articles

A SiC micro-structured neutron detector based on deep trench etching process

A SiC micro-structured neutron detector based on deep trench etching process

Preliminary benchmarks and analysis of boundary conditions in a trenched microstructured silicon radiation detector

Microstructured neutron detectors have the benefit of enhanced neutron detection efficiency as compared to planar devices, achieved by etching 6LiF-filled trenches on the top surface of a silicon PIN diode. This sensor geometry results in a complex electric field distribution and depletion characteristics within the diode under reverse bias. For the first time on record, the effects of a fixed oxide charge on the microstructured device depletion characteristics and mobile carrier transport is investigated. Prototype detectors were fabricated with non-conformal surface doping. Capacitance voltage and current voltage measurements were performed for these prototypes and compared with COMSOL Multiphysics simulations. A spectral response from an 241Am alpha particle source was acquired and analyzed. It was found that monoenergetic alpha particles produce three prominent peaks in the pulse height spectrum output by the device. The peaks were confirmed by simulations to correlate with dead layers and incident trajectories into the microstructure. It was also found that significant differences in pulse rise time result, corresponding with events arriving in a low-field region in the fins and a high-field region in the bulk. Geant4 was utilized for radiation transport, interaction modeling, and benchmarking the spectral data. The results of this simulation work provide confidence in the ability to attain and benchmark electrical characteristics and spectral data for semiconductor radiation detectors employing complex microstructures.

3D Microstructured Inorganic Perovskite Materials for Thermal Neutron Detection

AbstractA combination of novel techniques such as a solvent‐free thin‐film deposition, perovskite patterning, and 10B back‐fill technique enables the high neutron detection efficiency in a perovskite‐based microstructured thermal neutron detector. High‐efficiency cesium lead bromide (CsPbBr3) perovskite‐based microstructured detectors are demonstrated here. Trenches up to 10 µm deep are etched into the CsPbBr3 thin films using a novel dry etching process involving a combination of HBr and Ar plasma. The microstructured diodes are then backfilled with isotopically enriched boron as neutron conversion material via a sedimentation process to preserve the perovskite integrity. The fabricated microstructured CsPbBr3 thermal neutron detectors show an efficiency of 4.3%. This represents >1.2x efficiency improvement over planar silicon (3.5%) and >2x efficiency improvement over planar CsPbBr3 (2.1%) detectors, respectively. More importantly, gamma‐ray discrimination of 107 is measured in CsPbBr3‐based microstructured neutron detectors.

Simulation of GaN micro-structured neutron detectors for improving electrical properties**Project supported by the National Natural Science Foundation of China (Grant Nos. 11675198, 11875097, 11975257, 61774072, 61574026, and 61971090), the National Key Research and Development Program of China (Grant Nos. 2016YFB0400600 and2016YFB0400601), the Fundamental Research Funds for the Central Universities, China (Grant No. DUT19LK45), the China Postdoctoral Science Foundation (Grant No.

Nowadays, the superior detection performance of semiconductor neutron detectors is a challenging task. In this paper, we deal with a novel GaN micro-structured neutron detector (GaN-MSND) and compare three different methods such as the method of modulating the trench depth, the method of introducing dielectric layer and p-type inversion region to improve the width of depletion region (W). It is observed that the intensity of electric field can be modulated by scaling the trench depth. On the other hand, the electron blocking region is formed in the detector enveloped with a dielectric layer. Furthermore, the introducing of p-type inversion region produces new p/n junction, which not only promotes the further expansion of the depletion region but also reduces the intensity of electric field produced by main junction. It can be realized that all these methods can considerably enhance the working voltage as well as W. Of them, the improvement on W of GaN-MSND with the p-type inversion region is the most significant and the value of W could reach 12.8 μm when the carrier concentration of p-type inversion region is 1017 cm−3. Consequently, the value of W is observed to improve 200% for the designed GaN-MSND as compared with that without additional design. This work ensures to the researchers and scientific community the fabrication of GaN-MSND having superior detection limit in the field of intense radiation.

Fast-neutron detector developments for the TREAT hodoscope

This work describes the theoretical and experimental performances of four alternatives to the original Hornyak Button-type device that was used in the construction of the Transient Reactor Test (TREAT) Facility hodoscope. The alternatives considered differ in geometry, construction and detection materials to improve performance while decreasing some of the negative aspects of the original device. A Geant4 model of the original Hornyak Button was developed as a benchmark to validate the physics modeled, which agreed well with the reported values. The four alternatives considered were (1) a homogenized ZnS:Ag/PMMA rectangular bar outfitted with silicon photomultipliers (SiPMs), (2) a layered ZnS:Ag/PMMA rectangular bar detector also outfitted with SiPMs, (3) a microstructured neutron detector (MSND) backfilled with hydrogenous material and (4) a pressurized, organic gaseous scintillator. In two scintillation devices, SiPMs were considered as a replacement for photomultiplier tubes for greater light collection. These alternatives were considered as they each had the potential to provide better signal-to-noise ratios, reduce Čerenkov light production, increase detection efficiency, and/or improve neutron-to-gamma discrimination. At comparable lengths, the layered design has been experimentally determined to yield an efficiency of 1.3% (the Hornyak button exhibits 0.4%), while studies on the performances of the other detectors are still underway.

Process effects on leakage current of Si‐PIN neutron detectors with porous microstructure

Using the technique of Microfabrication, such as deep silicon dry etching, lithography, etc. Si‐PIN neutron detectors with porous microstructure have been successfully fabricated. In order to lower the leakage current, the key fabrication processes, including the Al windows opening, deep silicon etching and the porous side wall smoothing, have been optimized. The cross‐section morphology and current–voltage characteristics have been measured to evaluate the microfabrication processes. With the optimized conditions presented by the measurements, a neutron detector with a leakage current density of 2.67 μA cm−2 at a bias of −20 V is obtained. A preliminary neutron irradiation test with 252Cf neutron source has also been carried out. The neutron irradiation test shows that the neutron detection efficiency of the microstructured neutron detectors is almost 3.6 times higher than that of the planar ones.

Improved High Efficiency Stacked Microstructured Neutron Detectors Backfilled With Nanoparticle $^{6}$LiF

Silicon diodes with large aspect ratio trenched microstructures, backfilled with <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> LiF, show a dramatic increase in thermal neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology using detector stacking methods to increase thermal neutron detection efficiency, along with the current process to backfill <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> LiF into the silicon microstructures. The highest detection efficiency realized thus far is over 42% intrinsic thermal neutron detection efficiency by device-stacking methods. The detectors operate as conformally diffused pn junction diodes each having 1 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area. Two individual devices were mounted back-to-back with counting electronics coupling the detectors together into a single dual-detector device. The solid-state silicon device was operated at 3 V and utilized simple signal amplification and counting electronic components that have been adjusted from previous work for slow charge integration time. The intrinsic detection efficiency for normal-incident 0.0253 eV neutrons was found by calibrating against a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He proportional counter.