High Bias Voltage Research Articles

Progress in Hexagonal Boron Nitride (h-BN)-Based Solid-State Neutron Detector

This article will briefly review the progress of h-BN based solid-state metal semiconductor metal (MSM) neutron detectors. In the last decade, several groups have been working on hexagonal boron nitride (h-BN)-based solid-state neutron detectors. Recently, the detection efficiency of 59% has been reported. Efficient, low-cost neutron detectors made from readily available materials are essential for various applications. Neutron detectors are widely used to detect fissile materials and nuclear power plants for security applications. The most common and widely used neutron detectors are 3He based, which are sometimes bulky, difficult to transport, have high absorption length, need relatively high bias voltage (>1000 V), and have low Q-value (0.764 MeV). In addition, 3He is not a readily available material. Thus, there is a strong need to find an alternative detection material. The 10B isotope has a high neutron absorption cross-section, and it has been tested as a coating on the semiconducting materials. Due to the two-step process, neutron capture through 10B and then electron–hole pair generation in a typical semiconducting material, the efficiency of these devices is not up to the mark. The progress in h-BN based detectors requires a review to envision the further improvement in this technology.

High-power inductive coupler with a high-voltage DC blocker

The authors of this study developed a high-power inductive coupler with a high-voltage DC blocker that is capable of delivering up to 100 kW of CW RF power at 176 MHz and 4 kV DC. The high-power indictive coupler was developed at the Soreq Nuclear Research Center for the radio-frequency quadrupole of the Soreq Applied Research Accelerator Facility. The purpose of the DC blocker is to enable the application of high-voltage DC bias to the inner conductors of the couplers in order to prevent the multipacting phenomena. A new, mechanically and thermally improved, version of the RF coupler is designed and implemented in conjunction with the DC blocker. The underlying design principles, indigenous development, and results of tests of the coupler are presented here.

Bias voltage optimization and cutting performance of AlCrN coatings deposited by a hybrid technology

AlCrN coatings have been studied extensively by arc ion plating or magnetron sputtering, while there are scarce reports on the AlCrN coatings prepared by a hybrid technology of arc ion plating and magnetron sputtering. In this paper, five AlCrN coatings were prepared by the hybrid technology under bias voltages from −40 V to −200 V. XRD, SEM, TEM and nano-indenter etc. were used to study the microstructure and properties of the coatings. Results show that all the five coatings possess fcc-(Al,Cr)N phase with preferential orientation of (111) crystal plane. With higher bias voltage, the quantity of micro-particles decreases and the coating's surface quality is improved. Compressive stress, hardness and elastic modulus of the AlCrN coatings increase firstly and then decrease. The AlCrN coating with bias voltage of −160 V possesses the highest hardness about 33.2 GPa and lowest wear rate about 1.47 × 10−6 mm3/N‧m. The cutting time of the AlCrN coated cutter deposited at −160 V is 2.4 times longer than that of the uncoated milling cutter, with H13 die steel as work-piece. The AlCrN coated cutter fails mainly due to abrasive and adhesive wear. In addition, oxidation and inter-diffusion between substrate/coating/workpiece also occur in the cutting zone.

Design and evaluation of UKRI-MPW0: An HV-CMOS prototype for high radiation tolerance

High-Voltage CMOS (HV-CMOS) sensors are emerging as a prime candidate for future tracking applications that have extreme requirements on material budget, pixel granularity, time resolution and radiation tolerance. This article presents a new HV-CMOS prototype chip, UKRI-MPW0, aimed at pushing some of the boundaries of these sensors. This HV-CMOS chip implements a novel sensor cross-section which is optimised for backside biasing to unprecedented high voltages. Preliminary measurements have shown the chip is able to withstand high bias voltages (>600V) much beyond the state of the art, thus promising a large improvement in radiation tolerance. The design details and initial performance evaluation are presented in this paper.

Bilayer armchair graphene nanoribbon photodetector with Stone-Wales defect: A computational study

Bilayer armchair graphene nanoribbons (BAGNRs), due to their low sensitivity to low frequency noise and high controllability of their bandgap have drawn a lot of attention as building blocks of photodetectors in recent years. In this work, using tight binding (TB) method and non-equilibrium Green's function formalism (NEGF) a computational study has been done on the BAGNR photodetector with perfect and Stone-Wales (SW) defected channel and the effect of defects' number and position on the device performance has been investigated. In order to validate the TB parameters used in this work, the bandstructures of both perfect and SW defected BAGNRs are compared with the results of DFT method and a good matching is obtained. Simulation results show that perfect BAGNR photodetector has quantum efficiency (QE) of 19.77% at 0.12 eV photon energy. Among defected photodetectors, highest QE of 21.77% belongs to the structure with single SW defect near the right contact (higher bias voltage) at 0.14 eV. This structure also possesses the highest Iph/Idark of 64.45 which is 1.8 times larger than Iph/Idark of perfect BAGNR photodetector. Moreover, the structure with two SW defects located at left and right sides of the channel exhibits a drastically low Idark which results in a high Iph/Idark. In addition, this structure yields the high QE (19.72%) at blue-shifted photon energy of 0.2 eV which makes it a suitable choice for mid-wavelength infrared applications.

Amplification of photoelectric injection in the photodiode based on large-grain cadmium telluride films

The results of studies of photoelectric injection amplification in the Al–Al2O3–p-CdTe–Mo structure at high bias voltages for the forward current are presented. It has been shown that the spectral sensitivity reaches its maximum value Sλ = 8.4∙104 A/W, when the diode is illuminated with the “own” light at λ = 450 nm and V = 7 V, while when it is illuminated with the “impurity” light at λ = 950 nm Sλ = 4.3∙104 A/W under the same bias voltage. It has been established that when illuminating the structure with the “own” light, the positive feedback mechanism is realized, and when illuminating with “impurity” light, the parametric amplification mechanism is realized.

A high-entropy alloy nitride protective coating for fuel cladding in high temperature lead-bismuth eutectic alloy

High temperature coatings possess great potential for improving operation temperature of 4th generation nuclear reactor. In this paper, a high-entropy alloy nitride coatings (CrAlTiNbV)Nx were investigated for the application in corrosive lead-bismuth alloy (LBE). The coatings were synthesized by unbalanced magnetron sputtering on ferritic/martensitic (F/M) steel. Properties of (CrAlTiNbV)Nx are systematically investigated from perspective of the electron structure, crystalline, and mechanical properties under different bias voltage applied on samples. Significant improvement of hardness (30 GPa) is obtained at bias voltage of -156 V. Furthermore, the corrosion behavior in 550 °C lead bismuth eutectic (LBE) was conducted for 1200 h with saturated oxygen content, which demonstrates the dense structure of coatings with no obvious crack, spallation that characterized by the SEM, EDS, and TEM. Upon the application of high bias voltage, more prone formation of high-density grain boundary with fine grains extends the diffusion path of Pb and Bi are achieved for excellent LBE corrosion resistance. Our work not only provide an insight to the electron structure of high entropy alloy nitrides, but also shows a potential application for (CrAlTiNbV)Nx protecting fuel cladding in the next generation lead based reactor.

Highly Efficient Filterless Bilateral Majority Carrier‐Type Color Photodetectors

AbstractPhotodetectors (PDs) are essential for promoting the modern technology‐reliant lifestyles. Accordingly, the demand for efficient PDs with built‐in signal amplification capabilities is constantly increasing. Generally, built‐in signal amplification is achieved using an avalanching process that operates at a high bias voltage with inevitable excess noise. In this study, back‐to‐back Schottky diodes (BTB SDs) are designed to demonstrate a significant amplification of signals at low bias voltages with relatively low excess noise. Furthermore, the detection efficiency is bilateral and relies less on the illuminated junction or the bias polarity, but is influenced by the wavelength of the illuminating light owing to the specific device structures employed. This enables the identification of the color of the incident light without using any color filters. The BTB graphene–insulator–silicon‐on‐insulator (BTB G–I–SOI) PDs fabricated with controlled interfacial oxides exhibit photoresponsivity up to 2.01 × 104 A W−1, specific detectivity of 1.57 × 1014 cm Hz1/2 W−1 at 5 V, and a rapid response (≈0.3 ms) for a two‐millimeter‐long channel. Thus, BTB G–I–SOI PDs are highly efficient filterless color sensors that establish a novel route for diverse applications of PDs.

Evidence of cluster dipole states in germanium detectors operating at temperatures below 10 K

By studying charge trapping in germanium detectors operating at temperatures below 10 K, we demonstrate for the first time that the formation of cluster dipole states from residual impurities is responsible for charge trapping. Two planar detectors with different impurity levels and types are used in this study. When drifting the localized charge carriers created by α particles from the top surface across a detector at a lower bias voltage, significant charge trapping is observed when compared to operating at a higher bias voltage. The amount of charge trapping shows a strong dependence on the type of charge carriers. Electrons are trapped more than holes in a p-type detector, while holes are trapped more than electrons in an n-type detector. When both electrons and holes are drifted simultaneously using the widespread charge carriers created by γ rays inside the detector, the amount of charge trapping shows no dependence on the polarity of bias voltage.

Rapid Charge Storage and Release at Etching‐Assist Electret in Organic Transistors for Memories, Photodetectors, and Artificial Synapses

AbstractInsulator materials can trap charges, referring to electrets, which are attractive for transistors and memories. However, insulators intrinsically exhibit high electrical resistance, thus the charge injection and release inside insulators typically need high voltage or long bias time, limiting the applications that require high writing/erasing speed. In this work, insulator polymer polystyrene (PS) film is treated by a soft plasma, which selectively induces a high density of charge traps at the top surface, without changing the electronic properties of the underneath materials. The thus‐prepared surface is easily occupied by external neat charges to form a meso‐stable electret. Subsequently, the electret is used as an ultra‐thin charge trapping layer to build transistors for some applications. Consequently, in transistor architecture, the charge injection and release at soft plasma treated PS surface can be more easily achieved in a short stimulus as compared with pristine PS counterpart, and the density of captured holes under gate bias reaches 2.9 × 1012 cm−2 in 1 ms. Under UV irradiation, charge transfer occurs from the photo‐excited semiconductor to the electret, contributing to the rapid release of the stored holes. This soft plasma‐generated electret is then utilized for flash‐type memories, photodetectors, and artificial synapses.

Effects of surface topography at different scales on the dispersion of the wetting data for sessile water droplets on nitrided austenitic stainless steels

Plasma nitriding is used to increase the durability of steels. The wettability of nitrided surfaces is poorly studied. The ability of nitriding in modifying the wetting and evaporation of sessile droplets on austenitic stainless steel is studied. Transferred plasma for nitriding provides independent substrate biasing giving the opportunity to tailor the surface before and during the nitriding treatments. It was shown that a cleaning treatment (ArH2 plasma) produces topographical modifications of the surface by selective sputtering of the grains giving contact angles between 80 and 90°. Similar results are obtained when the nitriding treatments are carried out with a rather high bias voltage. It is explained using the skewness (Ssk) topographical roughness parameter which reveals the asymmetry of the profile. The more the Ssk is, the higher the contact angle is. During nitriding treatments, the very high internal stresses leads to the formation of spikes at the grain boundaries. Pinning of the three-phase contact line on peaks localized at grain boundaries are responsible for high contact angles. For nitriding treatments carried out with lower bias, surface contamination occurs and a discontinuous oxynitride layer is formed. The nanostructure formed by these oxides gives contact angles up to 120°.

Fast neutron irradiation effects on Si- and GaN-based avalanche photodiodes

We report the behaviour of the dark current and gain characteristics of Si- and GaN-based avalanche photodiodes (APDs) irradiated by fast neutrons. For Si-based APDs, the dark current increases with the increase of neutron fluence, indicating that the avalanche property has been seriously affected. The gain values of Si-based APD slightly increase after irradiation by a low neutron fluence of 1.0 × 1012 cm−2, while the device exhibits gain degradation as the fluence increases to 1.0 × 1013 cm−2 or even above at high reverse bias voltage, unlike the previous studies where only degradation was observed. The steep increase of dark current and gain when approaching the breakdown voltage after neutron irradiation indicate that the avalanche property is almost unaffected for GaN-based APDs. Furthermore, we infer that the optical absorption between acceptor state and conduction band in the p-type layer plays an important role in influencing the change of dark current and gain at high reverse bias voltage. The findings not only enrich the understanding of neutron irradiation effect on Si- and GaN-based APDs, but also experimentally prove that GaN-based APDs hold better radiation resistance than Si-based devices.

Effects of Shallow Carbon and Deep N++ Layer on the Radiation Hardness of IHEP-IME LGAD Sensors

Low-gain avalanche diode (LGAD) is the chosen technology for the ATLAS high-granularity timing detector (HGTD). According to previous studies, the acceptor removal effect due to the radiation and the single-event burnout (SEB) at high bias voltages are still a challenge for the LGAD. The Institute of High Energy Physics (IHEP), Beijing, China, cooperated with the Institute of Microelectronics (IME), Beijing, China, for the design and fabrication of the IHEP-IME LGAD sensors with shallow carbon and deep N++ layer to improve the radiation hardness of LGAD. After neutron irradiation up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5 \times 10^{15}\,\,{\mathrm{ n}}_{\mathrm{ eq}}$ </tex-math></inline-formula> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the leakage current, the collected charge, and timing resolution of the three IHEP-IME sensors measured with a beta telescope setup meet the HGTD requirements ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt; 125~\mu \text{A}$ </tex-math></inline-formula> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , >4 fC, and <70 ps). The LGAD sensor with shallow carbon had the lowest operation voltage after irradiation and is very promising to avoid the SEB effect. A sensor with a deep N++ layer increased the breakdown voltage of the LGAD with a high dopant concentration, which could alleviate the problem of the early breakdown of radiation-hard LGAD before irradiation.

Ultra-Low-Voltage Capacitive Micromachined Ultrasonic Transducers with Increased Output Pressure Due to Piston-Structured Plates.

Capacitive micromachined ultrasonic transducers (CMUTs) represent an accepted technology for ultrasonic transducers, while high bias voltage requirements and limited output pressure still need to be addressed. In this paper, we present a design for ultra-low-voltage operation with enhanced output pressure. Low voltages allow for good integrability and mobile applications, whereas higher output pressures improve the penetration depth and signal-to-noise ratio. The CMUT introduced has an ultra-thin gap (120 nm), small plate thickness (800 nm), and is supported by a non-flexural piston, stiffening the topside for improved average displacement, and thus higher output pressure. Three designs for low MHz operation are simulated and fabricated for comparison: bare plate, plate with small piston (34% plate coverage), and big piston (57%). The impact of the piston on the plate mechanics in terms of resonance and pull-in voltage are simulated with finite element method (FEM). Simulations are in good agreement with laser Doppler vibrometer and LCR-meter measurements. Further, the sound pressure output is characterized in immersion with a hydrophone. Pull-in voltages range from only 7.4 V to 25.0 V. Measurements in immersion with a pulse at 80% of the pull-in voltage present surface output pressures from 44.7 kPa to 502.1 kPa at 3.3 MHz to 4.2 MHz with a fractional bandwidth of up to 135%. This leads to an improvement in transmit sensitivity in pulsed (non-harmonic) driving from 7.8 kPa/V up to 24.8 kPa/V.

Transient analysis of photomultiplication-type organic photodiodes

Photomultiplication-type organic photodetectors have emerged as a class of next generation solution-processed photodetectors with high gain. Despite this promising feature, the reported photodectors still suffer from relatively large dark currents at high bias voltages. To overcome this drawback, a mechanistic understanding of the photomultiplication effect in organic photodiodes is required. In this work, we advanced the performance of photomultiplication-type organic photodetectors by tuning the active layer composition and interfacial layers. The optimized devices exhibit small dark currents and flat dark current–voltage curves under the reverse bias condition up to −10 V. The optimized photodetectors also reached an ultra-high responsivity of 23.6 A/W and the specific detectivity of 1.04 × 1012 Jones at −10 V. More importantly, we investigated the photomultiplication process with multiple transient techniques and revealed that the photoconductive gain effect is a slow process, which relies on the photo-Schottky effect enabled by charge carrier tunneling and the accumulation of holes. Furthermore, we also demonstrated prototypical pulsed-light detection based on the optimized devices, which showed great potential for real applications.

A high voltage capacitance measurement method based on alternating coupled signal injection.

As high voltage pulse power capacitors, ceramic capacitors are widely used in high voltage pulse generators, trigger circuits, laser generators, and other fields. The capacitance of ceramic capacitors is closely related to the direct current (DC) bias voltage. However, the current capacitance measurement methods can only achieve a DC bias of 1 kV, which cannot meet the measurement requirements in high voltage environments. This paper proposes a capacitance measurement method that can accurately measure the capacitance under a DC bias of 3 kV. This method decouples the high DC bias voltage and high frequency alternating small signals and realizes low voltage calibration and high voltage isolation. The experimental results show that the proposed method measures the capacitance under a DC bias of 3 kV with a relative error within ±1%, which makes it possible to accurately quantify the capacitance hysteresis deviation in the process of increasing and decreasing back the voltage.

Single-molecule field effect and conductance switching driven by electric field and proton transfer.

Single-molecule junctions (SMJs) offer a novel strategy for miniaturization of electronic devices. In this work, we realize a graphene-porphyrin-graphene SMJ driven by electric field and proton transfer in two configurations. In the transistor configuration with ionic liquid gating, an unprecedented field-effect performance is achieved with a maximum on/off ratio of ~4800 and a gate efficiency as high as ~179 mV/decade in consistence with the theoretical prediction. In the other configuration, controllable proton transfer, tautomerization switching, is directly observed with bias dependence. Room temperature proton transfer leads to a two-state conductance switching, and more precise tautomerization is detected, showing a four-state conductance switching at high bias voltages and low temperatures. Such an SMJ in two configurations provides new insights into not only building multifunctional molecular nanocircuits toward real applications but also deciphering the intrinsic properties of matters at the molecular scale.

Temperature dependent erosion and Raman analyses of arc-deposited H free thick DLC coating on Cr/CrN coated plasma nitrided steel

Development of H and metal dopant-free single phase thick diamond like carbon (DLC) coating on metal nitride layer for automobile applications is still a challenging task due to internal stress developed during deposition of DLC films. A simple process was followed to deposit thick Cr/CrN/DLC (0.25/0.75/6 μm) coating on plasma nitrided steel using an un-filtered cathodic vacuum arc system without applying any high pulse bias voltage. In addition, the coating was deposited at room temperature and it showed very good adhesion on plasma nitrided steel surface and exhibited a very low coefficient of friction ~0.06 ± 0.005. Temperature dependent solid particle erosion tests were conducted according to ASTM-G-76-18 standards at an impinging angle of 45°. Erosion resistance of the coating is 33, 11, 7 and 6 times better than nitrided steel substrate at test temperatures of 25, 200, 300 and 400 °C, respectively. Better erosion resistance performance of a coating infers the long life of the coating on automobile components. A multi-wavelength Raman study gives a better understanding of the structural properties of DLC. So, the Raman spectra of the coating were recorded using three different laser wavelengths: 405 nm, 532 nm and 633 nm. The thermal stability of the coating was studied using temperature dependent Raman spectroscopy. The coating showed good thermal stability until a temperature of 425 °C.

In Situ Monitoring of Transmetallation in Electric Potential-Promoted Oxidative Coupling in a Single-Molecule Junction

In Situ Monitoring of Transmetallation in Electric Potential-Promoted Oxidative Coupling in a Single-Molecule Junction

Bias-dependent two-phase anisotropy in magnetoresistance of a GaMnAs-based magnetic tunnel junction

We report unique two-phase anisotropy in the tunnel magnetoresistance (TMR) of a GaMnAs-based magnetic tunnel junction, obtained by investigating the magnetic-field-direction dependence with various applied bias voltages. The TMR shows two-fold symmetry about the axis at a low bias voltage, while at higher bias voltages, it shows four-fold symmetry about the 〈100〉 axis in the large magnetic field H region. Considering modified Jullière’s model and multiple bands with different anisotropic features, we can well reproduce the experimental TMR characteristics. Our results will lead to novel functionalities using TMRs with different symmetries in multi-orbital materials.