Search Results (16)

Sn-doped Ga₂O₃ thin films and metal–semiconductor–metal (MSM) ultraviolet detectors were prepared using the co-sputtering method to enhance their photoelectric performance. The results revealed that Sn doping can effectively change the optical and electrical properties of thin films, greatly improving the photoelectric responsiveness of the devices. Through microstructure testing results, all of the thin film structures were determined to be monoclinic beta phase gallium oxide. At a DC power of 30 W, the thickness of the Sn-doped thin film was 430 nm, the surface roughness of the thin film was 4.94 nm, and the carrier concentration, resistivity, and mobility reached 9.72 × 10¹⁸ cm⁻³, 1.60 × 10⁻⁴ Ω·cm, and 45.05 cm³/Vs, respectively. The optical results show that Sn doping clearly decreases the transmission of thin films and that the bandgap can decrease to 3.91 eV. Under 30 W DC power, the photo dark current ratio of the detector can reach 101, time responses of t_r = 31 s and t_f = 22.83 s were obtained, and the spectral responsivity reached 19.25 A/W. Full article

The main consequence of radiation damage on a silicon photomultiplier (SiPM) is a significant increase in the dark current. If the SiPM is not adequately cooled, the power dissipation causes it to heat up, which alters its performance parameters. To investigate this heating effect, a measurement cycle was developed and performed with a KETEK SiPM glued to an Al₂O₃ substrate and with HPK SiPMs glued to either an Al₂O₃ substrate or a flexible PCB. The assemblies were connected either directly to a temperature-controlled chuck on a probe station, or through layers of materials with defined thermal resistance. An LED operated in DC mode was used to illuminate the SiPM and to tune the power dissipated in a measurement cycle. The SiPM current was used to determine the steady-state temperature reached by the SiPM via a calibration curve. The increase in SiPM temperature due to self-heating is analyzed as a function of the power dissipation in the SiPM and the thermal resistance. This information can be used to adjust the operating voltage of the SiPMs, taking into account the effects of self-heating. Similarly, this approach can be applied to investigate the unknown thermal contact of packaged SiPMs. Full article

The aim of this work is to investigate the degradation of perovskite solar cells (PSCs) by means of impedance spectroscopy, a highly sensitive characterization technique used to establish the electrical response of a device in a nondestructive manner. In this paper, PSCs with two different electron transport layers (ETLs) are studied: PSCs with undoped SnO₂ as an ETL are compared to PSCs with an ETL composed of graphene-doped SnO₂ (G-SnO₂). Experimental data were collected immediately after fabrication and after one week, monitoring both impedance spectroscopy and dark current-voltage (I-V) curves. It was observed that, in the case of the undoped PSCs, the degradation of the solar cells affected both the AC behavior of the devices, modifying the associated Nyquist plots, and the DC behavior, observable from the dark I-V measurements. Conversely, the solar cells with G-SnO₂ showed no variation. Considering the Nyquist plots, a quantitative analysis was performed by comparing the parameters of a proper equivalent circuit model. The results were coherent with those achieved in the DC analysis, thus proving that the analysis of impedance spectra, supported with dark I-V curves, allows one to gain a deeper knowledge of the degradation phenomena of perovskite solar cells. This study opens the door for further improvement of these devices through a better understanding of their electrical behavior. Full article

Using a new implantation technique with multielement molecular ions consisting of carbon, hydrogen, and phosphorus, namely, CH₂P molecular ions, we developed an epitaxial silicon wafer with proximity gettering sinks under the epitaxial silicon layer to improve the gettering capability for metallic impurities. A complementary metal-oxide-semiconductor (CMOS) image sensor fabricated with this novel epitaxial silicon wafer has a markedly reduced number of white spot defects, as determined by dark current spectroscopy (DCS). In addition, the amount of nickel impurities gettered in the CH₂P-molecular-ion-implanted region of this CMOS image sensor is higher than that gettered in the C₃H₅-molecular-ion-implanted region; and this implanted region is formed by high-density black pointed defects and deactivated phosphorus after epitaxial growth. From the obtained results, the CH₂P-molecular-ion-implanted region has two types of complexes acting as gettering sinks. One includes carbon-related complexes such as aggregated C–I, and the other includes phosphorus-related complexes such as P₄–V. These complexes have a high binding energy to metallic impurities. Therefore, CH₂P-molecular-ion-implanted epitaxial silicon wafers have a high gettering capability for metallic impurities and contribute to improving the device performance of CMOS image sensors. (This manuscript is an extension from a paper presented at the 6th IEEE Electron Devices Technology & Manufacturing Conference (EDTM 2022)). Full article

The reduction of the dark current (DC) to a tolerable level in amorphous selenium (a-Se) X-ray photoconductors was one of the key factors that led to the successful commercialization of a-Se-based direct conversion flat panel X-ray imagers (FPXIs) and their widespread clinical use. Here, we discuss the origin of DC in another X-ray photoconductive structure that utilizes amorphous lead oxide (a-PbO) as an X-ray-to-charge transducer and polyimide (PI) as a blocking layer. The transient DC in a PI/a-PbO detector is measured at different applied electric fields (5–20 V/μm). The experimental results are used to develop a theoretical model describing the electric field-dependent transient behavior of DC. The results of the DC kinetics modeling show that the DC, shortly after the bias application, is primarily controlled by the injection of holes from the positively biased electrode and gradually decays with time to a steady-state value. DC decays by the overarching mechanism of an electric field redistribution, caused by the accumulation of trapped holes in deep localized states within the bulk of PI. Thermal generation and subsequent multiple-trapping (MT) controlled transport of holes within the a-PbO layer governs the steady-state value at all the applied fields investigated here, except for the largest applied field of 20 V/μm. This suggests that a thicker layer of PI would be more optimal to suppress DC in the PI/a-PbO detector presented here. The model can be used to find an approximate optimal thickness of PI for future iterations of PI/a-PbO detectors without the need for time and labor-intensive experimental trial and error. In addition, we show that accounting for the field-induced charge carrier release from traps, enhanced by charge hopping transitions between the traps, yields an excellent fit between the experimental and simulated results, thus, clarifying the dynamic process of reaching a steady-state occupancy level of the deep localized states in the PI. Practically, the electric field redistribution causes the internal field to increase in magnitude in the a-PbO layer, thus improving charge collection efficiency and temporal performance over time, as confirmed by experimental results. The electric field redistribution can be implemented as a warm-up time for a-PbO-based detectors. Full article

A new fall rye (FR, Secale cereale L.) cv. Bono was investigated as a novel cropping option in Saskatchewan, Canada. In this study, the performance of Bono was compared to Hazlet FR, and both cultivars were compared to winter triticale (WT, Triticosecale Wittm.) cv. Pika in single cropping (SC) or in double cropping (DC) systems with spring barley (Hordeum vulgare L.) was evaluated in the Dark Brown soil zone, 2019–2021. Five replicated (n = 4) treatments were: (i) BonoFR; (ii) HazletFR; (iii) PikaWT; (iv) Barley–BonoFR; and (v) Barley–HazletFR. The first crop of barley was harvested at soft dough stage, followed by the second crop of FR seeded in the same year and harvested between flag leaf to heading emergence the following summer for greenfeed hay. Bono did not differ (p > 0.05) in DMY (1.2 Mg ha⁻¹) or nutritive value from Hazlet, however, both FRs differed (p = 0.01) from WT by higher nitrogen use efficiency (NUE, 41.0 vs. 33.7) and NDF (541.8 vs. 479.3 g kg^–1), but lower CP (155.3 vs. 187.1 g kg^–1). Double cropping barley with fall ryes increased total DMY, nutrients yield per ha, and minerals uptake by up to 83% and NUE by 35.3%. In conclusion, Bono fall rye could be an equal quality alternative to Hazlet, although the current higher seed price may delay its adoption. Full article

Towards the next generation of compact plasma-based accelerators, useful in several fields, such as basic research, medicine and industrial applications, a great effort is required to control the plasma creation, the necessity of producing a time-jitter free channel, and its stability namely uniformity and reproducibility. In this Letter, we describe an experimental campaign adopting a gas-filled discharge-capillary where the plasma and its generation are stabilized by triggering its ignition with an external laser pulse or an innovative technique based on the primary dark current (DC) in the accelerating structure of a linear accelerator (LINAC). The results show an efficient stabilization of the discharge pulse and plasma density with both pre-ionizing methods turning the plasma device into a symmetrical stable accelerating environment, especially when the external voltage is lowered near the breakdown value of the gas. The development of tens of centimeter long capillaries is enabled and, in turn, longer acceleration lengths can be adopted in a wide range of plasma-based acceleration experiments. Full article

Research has shown that both dark chocolate and exercise training may have favorable effects on antioxidant function in obese cohorts. However, their combined effect has not been established. We assessed the influences of six weeks of dark chocolate consumption combined with jump rope exercise on antioxidant markers in adolescent boys with obesity. Fifty adolescent boys with obesity (age = 15 ± 1 years) were randomly assigned into one of four groups; jump rope exercise + white chocolate consumption (JW; n = 13), jump rope exercise + dark chocolate consumption (JD; n = 13), dark chocolate consumption (DC; n = 12), or control (C; n = 12). Two participants dropped out of the study. Participants in JW and JD groups performed jump rope exercise three times per week for six weeks. Participants in the DC and JD groups consumed 30 g of dark chocolate containing 83% of cocoa during the same period. Serum concentrations of superoxide dismutase (SOD), total antioxidant capacity (TAC), glutathione peroxidase (GPx), and thiobarbituric acid reactive substances (TBARS) were evaluated prior to and after the interventions. All 3 intervention groups noted significant (p < 0.01) increases in serum concentrations of TAC, SOD, and GPx from baseline to post-test. In contrast, all intervention groups showed significantly reduced serum concentrations of TBARS from pre- to post-test (p ≤ 0.01). Bonferroni post hoc analysis revealed that post-test serum concentrations of TAC in the JD group were significantly greater than C (p < 0.001), DC (p = 0.010), and JW (p < 0.001) groups. In addition, post-test serum concentrations of SOD in the JD group were significantly greater than C group (p = 0.001). Post-test serum concentrations of GPx in the JD group were significantly greater than C (p < 0.001), DC (p = 0.021), and JW (p = 0.032) groups. The post-test serum concentrations of TBARS in the JD group was significantly lower than C (p < 0.001). No other significant between-group differences were observed. The current study provides evidence that dark chocolate consumption in combination with jump rope exercise is more efficient in improving antioxidant capacity than dark chocolate consumption or jump rope exercise alone among obese adolescent boys. Full article

Chocolate masses are one of the basic raw materials for the production of confectionery. Knowledge of their rheological and flow behaviour at different temperatures is absolutely necessary for the selection of a suitable technological process in their production and subsequent processing. In this article, the rheological properties (the effect of the shear strain rate on the shear stress or viscosity) of five different chocolate masses were determined—extra dark chocolate (EDC), dark chocolate (DC), milk chocolate (MC), white chocolate (WC), and ruby chocolate (RC). These chocolate masses showed thixotropic and plastic behaviour in the selected range of shear rates from 1 to 500 s⁻¹ and at the specified temperatures of 36, 38, 40, 42, and 44 °C. The degree of thixotropic behaviour was evaluated by the size of the hysteresis area, and flow curves were constructed using the Bingham, Herschel–Bulkley and Casson models with respect to the plastic behaviour of the chocolate masses. According to the values of the coefficients of determination R² and the sum of the squared estimate of errors (SSE), the models were chosen appropriately. The most suitable models are the Herschel–Bulkley and Casson models, which also model the shear thinning property of the liquids (pseudoplastic with a yield stress value). Using the coefficients of the rheological models and modified equations for the flow velocity of technical and biological fluids in standard piping, the 2D and 3D velocity profiles of the chocolate masses were further successfully modelled. The obtained values of coefficients and models can be used in conventional technical practice in the design of technological equipment structures and in current trends in the food industry, such as 3D food printing. Full article

Soybean production in the system of organic agriculture is not very demanding, and this has been well documented both through experimental results and commercial production. However, one of the biggest problems in organic production is the lack of adequate pre-sowing treatments. Therefore, the aim of this study was to examine the effect of the electrostatic field. This is a physical treatment that was first used for seed treatment in the 18th century but has mostly been neglected since then. Seeds of five soybean genotypes with differently colored seed coats (yellow, green, dark green, brown, and black) were included in this study. The seeds were exposed to different values of direct current (DC) with the following voltages: 0 V (control), 3 V, 6 V, and 9 V, to which the seeds were exposed for 0 min (control), 1 min, and 3 min. After exposing the seeds to the electric field, the physiological properties of seeds and seedlings at the first stage of growth were evaluated. The results show that the effect of the electrostatic field on seed quality depends on the genotype, voltage, and exposure time. The application of DC can be a suitable method for improving seed germination and the initial growth of soybean seedlings. In addition, the results indicate that it is necessary to adjust the DC treatment (voltage and duration of exposure of seeds) to particular genotypes since inadequate treatments may reduce the quality of seeds. Full article

In the field of near-infrared weak light detection, an InP/InGaAs single-photon avalanche diode (SPAD) is preferred due to the advantages of high sensitivity, low cost and room-temperature operation. To properly simulate and optimize the SPAD’s front-end circuit, a comprehensive and compact behavior model of the InP/InGaAs SPAD is normally required to accurately describe the statistical behavior of the detectors. In this paper, an InP/InGaAs SPAD analytical model is constructed, which not only includes the direct current (DC) and alternating current (AC) behavior simulating the avalanche and quenching processes, but also describes the dark count, after-pulsing and photon detection efficiency. For dark count noise, three important generation mechanisms are considered, including thermal generation, trap-assisted tunneling and band-to-band tunneling. The model described by the Verilog-A hardware description language (HDL) can be directly implemented in the commercial circuit simulator. A gated mode, passive quenching and recharging circuit is used to simulate and verify the developed model. The simulation results are in good agreement with the reported test data, demonstrating the accuracy of the developed InP/InGaAs SPAD model. Full article

We present and discuss parameters of a high dynamic range (HDR) image sensor with LED flicker mitigation (LFM) operating in automotive temperature range. The total SNR (SNR including dark fixed pattern noise), of the sensor is degraded by floating diffusion (FD) dark current (DC) and dark signal non-uniformity (DSNU). We present results of FD DC and DSNU reduction, to provide required SNR versus signal level at temperatures up to 120 °C. Additionally we discuss temperature dependencies of quantum efficiency (QE), sensitivity, color effects, and other pixel parameters for backside illuminated image sensors. Comparing +120 °C junction vs. room temperature, in visual range we measured a few relative percent increase, while in 940 nm band range we measured 1.46x increase in sensitivity. Measured change of sensitivity for visual bands—such as blue, green, and red colors—reflected some impact to captured image color accuracy that created slight image color tint at high temperature. The tint is, however, hard to detect visually and may be removed by auto white balancing and temperature adjusted color correction matrixes. Full article

In this paper we present a systematic approach to sort out different types of random telegraph noises (RTN) in CMOS image sensors (CIS) by examining their dependencies on the transfer gate off-voltage, the reset gate off-voltage, the photodiode integration time, and the sense node charge retention time. Besides the well-known source follower RTN, we have identified the RTN caused by varying photodiode dark current, transfer-gate and reset-gate induced sense node leakage. These four types of RTN and the dark signal shot noises dominate the noise distribution tails of CIS and non-CIS chips under test, either with or without X-ray irradiation. The effect of correlated multiple sampling (CMS) on noise reduction is studied and a theoretical model is developed to account for the measurement results. Full article

AC photoelectrochemical imaging at electrolyte–semiconductor interfaces provides spatially resolved information such as surface potentials, ion concentrations and electrical impedance. In this work, thin films of InGaN/GaN were used successfully for AC photoelectrochemical imaging, and experimentally shown to generate a considerable photocurrent under illumination with a 405 nm modulated diode laser at comparatively high frequencies and low applied DC potentials, making this a promising substrate for bioimaging applications. Linear sweep voltammetry showed negligible dark currents. The imaging capabilities of the sensor substrate were demonstrated with a model system and showed a lateral resolution of 7 microns. Full article

In free space optical communications, long-distance transmission leads to the attenuation of beacon light, where we adopt a quadrant detector (QD) to receive the weak signal. However, the background light interferes so strongly that the output signal-to-noise ratio (SNR) of QD is at a low level, which causes a decrease in accuracy of the direct detection method. This requires finding a new light spot detection method, so an improved detection method is proposed. Because the dark current noise and the background light noise are both white noise, we adopt a Kalman filter to estimate the real output of four electric signals of QD. Unfortunately, running these through an amplifier introduces some direct current (DC) offsets into the signals. In order to balance the effect of the DC offsets, we consider using the modulation method, where we employ a sine signal to modulate the intensity of the beacon light at the transmitting end, after which we can give an inverse gain to move the center of signals to near zero to eliminate the DC offsets when we calculate the data. In Kalman filtering, we use the peak values of the signals in every period after the analog to digital converter (ADC) as the elements of the measurement matrix. Experimental results show that even when QD output SNR is about −10 dB, the detection root-mean-square errors decrease by 51.5% using the improved detection method compared with the direct detection method. Moreover, Kalman filtering does not require a large amount of data, which means it works efficiently, can reduce the cost of hardware resources, and is available for the real-time calculation of spot position. Full article