Search Results (164)

This paper proposes a dual-mode CMOS analog front-end (AFE) circuit for short-wave infrared (SWIR) image sensors, which integrates a hybrid readout circuit (ROIC) and a 12-bit two-step single-slope analog-to-digital converter (TS-SS ADC). The ROIC dynamically switches between buffered-direct-injection (BDI) and direct-injection (DI) modes, thus balancing injection efficiency against power consumption. While the DI structure offers simplicity and low power, it suffers from unstable biasing and reduced injection efficiency under high background currents. Conversely, the BDI structure enhances injection efficiency and bias stability via an input buffer but incurs higher power consumption. To address this trade-off, a dual-mode injection architecture with mode-switching transistors is implemented. Mode selection is executed in-pixel via a low-leakage transmission gate and coordinated by the column timing controller, enabling low-current pixels to operate in low-noise BDI mode, whereas high-current pixels revert to the low-power DI mode. The TS-SS ADC employs a four-terminal comparator and dynamic reference voltage compensation to mitigate charge leakage and offset, which improves signal-to-noise ratio (SNR) and linearity. The prototype occupies 2.1 mm × 2.88 mm in a 0.18 µm CMOS process and serves a 64 × 64 array. The AFE achieves a dynamic range of 75.58 dB, noise of 249.42 μV, and 81.04 mW power consumption. Full article

This paper presents the design, fabrication, calibration, and comprehensive characterization of a homemade tri-axial fluxgate magnetometer. The magnetometer, utilizing a ring core configuration, was developed to measure ultra-low magnetic fields with high sensitivity and stability. Critical stages from material selection to sensor geometry optimization are discussed in detail. A series of critical characterization processes were conducted, including zero-field voltage determination, scale factor calculation, resolution measurement, noise analysis, bias assessment, cross-field effect evaluation, temperature dependency, and bandwidth determination. The sensor demonstrated a minimum detectable magnetic field resolution of 2.2 nT with a noise level of 1.1 nT/√Hz at 1 Hz. Temperature dependency tests revealed minimal impact on sensor output with a maximum shift of 120 nT in the range of 60 °C, which was effectively compensated through calibration to less than 5 nT. Additionally, the paper introduces a model function in matrix form to relate the magnetometer’s output voltage to the measured magnetic field, incorporating temperature dependency and cross-field effects. This work highlights the importance of meticulous calibration and optimization in developing fluxgate magnetometers suitable for various applications, from space exploration to biomedical diagnostics. Full article

In this paper, a capacitively coupled-fed reconfigurable wideband bandpass filter (BPF) is proposed based on liquid crystal (LC) technology, which achieved three transmission poles across varying bias voltages (V_B). An open-ended stepped impedance resonator configuration enables multi-mode resonance, offering significantly wider bandwidth compared to uniform-impedance resonators. The fractional bandwidth (FBW) and transmission pole positions are determined by the impedance ratio of the two resonators, allowing the filter to meet specific design requirements. An analytical methodology employing multilayer transmission line formulations and resonant frequency ratios was used to predict the modal stability of transmission poles under dielectric constant variation, which was subsequently validated through simulation. Experimental results show that the center frequency can be adjusted from 10.76 to 9.47 GHz with a maximum V_B of 30 V, achieving a tuning range of 12.71%. The normalized 3 dB FBW exceeds 64.66%, and the return loss remains above 10 dB from 0 to 30 V, offering the widest FBW among the reported LC BPFs without pole merging or mode collapse. The frequency response of the fabricated filter shows good agreement with the simulation results. Full article

This study investigates the degradation mechanisms of 1200 V SiC MOSFETs during High-temperature Reverse Bias (HTRB) reliability testing, focusing on breakdown voltage (BV) reduction. Experimental results reveal that trapped charges at the SiC/SiO₂ interface in the termination region alter electric field distribution, leading to premature breakdown. To address this issue, an optimized termination structure is proposed, incorporating reduced spacing between adjacent field rings and additional outer rings. TCAD simulations and experimental validation demonstrate that the improved design stabilizes BV within 2% deviation during 1000 h HTRB testing, which significantly enhances termination robustness. Full article

Al-Cr-N ternary coatings were deposited on the surface of Cr12MoV alloy tool steel via multiarc ion plating technology. The microstructure and mechanical and tribological properties of these coatings were systematically characterized, analyzed, and compared with those of the uncoated substrate specimens. The results indicated that under optimal conditions, Al70Cr30 alloy was effectively ionized, leading to the formation of AlN and CrN phases between Al ions, Cr ions, and nitrogen atoms. These phases were uniformly distributed within the coating, forming an ordered lattice structure. At a bias voltage of −60 V, the deposited Al-Cr-N coating exhibited a uniform and smooth morphology. However, because of the inherent characteristics of arc deposition, droplets and craters were observed on the coating surface as a result of sputtering and back-sputtering effects. The average nanohardness of the Al-Cr-N ternary coating reached 23.8 ± 3.1 GPa, while the coefficient of friction stabilized at approximately 0.7 during the wear process, compared with around 0.8 for the uncoated Cr12MoV substrate. Compared with the uncoated Cr12MoV substrate, the Al-Cr-N coating demonstrated significantly enhanced hardness and wear resistance, thereby effectively improving the performance of Cr12MoV alloy tool steel. Full article

This study proposed an innovative method for growing gate oxide on silicon carbide (SiC), where silicon oxide (SiO₂) was fabricated on a deposited Al₂O₃ layer, achieving high quality gate oxide. A thin Al₂O₃ passivation layer was deposited via atomic layer deposition (ALD), followed by Si deposition and reoxidation to fabricate a MOS structure. The effects of different ALD growth cycles on the interface chemical composition, trap density, breakdown characteristics, and bias stress stability of the MOS capacitors were systematically investigated. X-ray photoelectron spectroscopy (XPS) analyses revealed that an ALD Al₂O₃ passivation layer with 10 growth cycles effectively suppresses the formation of the proportion of Si-O_xC_y bonds. Additionally, the SiO₂/Al₂O₃/SiC gate stack with 10 ALD growth cycles exhibited optimal electrical properties, including a minimum interface state density (D_it) value of 3 × 10¹¹ cm⁻² eV⁻¹ and a breakdown field (E_bd) of 10.9 MV/cm. We also systematically analyzed the bias stress stability of the capacitors at room temperature and elevated temperatures. Analysis of flat-band voltage (ΔV_fb) and midgap voltage (ΔV_mg) hysteresis after high-temperature positive and negative bias stress demonstrated that incorporating a thin Al₂O₃ layer at the interface is the key factor in enhancing the stability of V_fb and midgap voltage V_mg. Full article

Schottky barrier thin-film transistors (SBTFTs) are promising for low-power electronics due to advantages such as low saturation voltage and high stability. In this study, we developed a high-performance bilayer IGZO SBTFT by combining a 4.7 nm atomic layer deposition (ALD) IGZO layer with an 11.8 nm sputtering IGZO layer, using platinum (Pt) and molybdenum (Mo) electrodes. The device exhibits dual-mode operation. In Schottky barrier TFT (SB-TFT) mode (Pt as source), the bilayer structure reduces defect density, achieving a very low saturation voltage (~0.4 V), high field-effect mobility (up to 20 cm²/V·s), and enhanced stability under stress conditions, including positive/negative bias and negative illumination. In quasi-Ohmic TFT (QO-TFT) mode (Pt as drain), the device retains conventional saturation behavior in output characteristics while delivering similar mobility and robust stability. This work provides a novel bilayer SBTFT design with dual functionality, enabling a higher current drive, improved stability, and flexibility for energy-efficient applications. Full article

To address the bias drift problem and hysteresis phenomenon of hemispherical resonator gyroscope (HRG) under temperature change, a temperature drift compensation method based on internal parameters is proposed. The influence model of zero-rate output bias is established with the parameters such as resonance frequency, driving signal amplitude and quadrature suppression voltage amplitude during HRG operation. The temperature cycle experiment is carried out in the range of −20 to 60 °C, and the relationship between internal parameters and working temperature is revealed. Using KAN neural network combined with time series data as input features, a real-time compensation model is designed to effectively improve the prediction accuracy of hysteresis phenomenon. The experimental results show that the model significantly reduces the output stability performance of HRG, from 0.022°/h to 0.013°/h, and the stability decreases from 1.1392°/h to 0.0651°/h, which improves the stability and reliability of HRG. Full article

A two-step annealing treatment was applied on a fully transparent amorphous InGaZnO4 (a-IGZO) top-gate thin-film transistor (TG-TFT) to improve the device performance. The electrical properties and stabilities of a-IGZO TG TFTs were significantly improved as the first-annealing temperature increased from 150 °C to 350 °C with a 300 °C second-annealing treatment. The a-IGZO TG-TFT with the 300 °C first-annealing treatment demonstrated the overall best performance, which has a mobility of 13.05 cm²/(V·s), a threshold voltage (V_th) of 0.33 V, a subthreshold swing of 130 mV/dec, and a I_on/I_off of 1.73 × 10⁸. The V_th deviation (ΔV_th) was −0.032 V and −0.044 V, respectively, after a 7200 s positive and negative bias stress under the gate bias voltage V_G = ±3 V and V_D = 0.1 V. The Photoluminescence spectra results revealed that the distribution and the density of defects in a-IGZO films were changed after the first-annealing treatment, whereas the X-ray photoelectron spectroscopy results displayed that contents of the oxygen vacancy and Ga-O bond varied in annealed a-IGZO films. In addition, a-IGZO TG-TFTs had achieved a transmittance of over 90%. Research on the effects of the first-annealing treatment will contribute to the fabrication of highly stable top-gate TFTs in the fields of transparent flexible electronics. Full article

Interface-passivated graphene/silicon Schottky junction solar cells have demonstrated promising features with improved stability and power conversion efficiency (PCE). However, there are some misunderstandings in the literature regarding some of the working mechanisms and the impacts of the silicon/insulator interface. Specifically, attributing performance improvement to oxygen vacancies and characterizing performance using Schottky barrier height and ideality factor might not be the most accurate or appropriate. This work uses Al₂O₃ as an example to provide a detailed discussion on the interface ALD growth of Al₂O₃ on silicon and its impact on graphene electrode metal–insulator–semiconductor (MIS) solar cells. We further suggest that the current conduction in MIS solar cells with an insulating layer of 2 to 3 nm thickness is better described by direct tunneling, Poole–Frenkel emission, and Fowler–Nordheim tunneling, as the junction voltage sweeps from negative to a larger forward bias. The dielectric film thickness, its band offset with Si, and the interface roughness, are key factors to consider for process optimization. Full article

The growing demand for high-performance oxide transistors in advanced integrated circuits (ICs) underscores the need for innovative device structures, with heterojunctions emerging as a promising approach. This study presents high-performance ITO/ZnO transistors, which outperform individual ITO or ZnO transistors by achieving an on-state current of 19.2 μA/μm at a drain voltage of 1 V and exhibiting a minimal threshold voltage shift of −0.16 V under negative bias illumination stress. Band structure analysis reveals that the differences in the conduction band minimum and Fermi level between the ZnO and ITO films lead to the formation of a potential well at the ITO/ZnO interface. Furthermore, the increase in the on-state current is attributed to electron confinement at the ITO/ZnO interface, while the enhanced NBIS stability is ascribed to both the band structure and ZnO passivation. These findings make significant contributions to both optimizing the performance and analyzing the mechanisms of oxide devices, highlighting the potential of high-performance ITO/ZnO transistors in 3D integrated circuits, advanced memory devices, and back-end-of-line (BEOL) processes. Full article

In this work, a tachometer based on a Metglas/PZT/Metglas magnetoelectric (ME) composite was developed to achieve high-precision rotational speed measurement over a wide temperature range (−70 °C to 160 °C). The tachometer converts external magnetic signals into electrical signals through the ME effect and operates stably in extreme temperature environments. COMSOL Multiphysics software was used for simulation analysis to investigate the ME response characteristics of the composite in such environments. To evaluate the properties of the ME composite under different conditions, its response characteristics at various frequencies, DC bias, and temperatures were systematically investigated. A permanent magnet and a DC motor were used to simulate gear rotation, and the voltage output was analyzed by adjusting the position between the sensor and the DC motor. The results show that the measured values of the ME tachometer closely match the set values, and the tachometer demonstrates high measurement accuracy within the range of 480 to 1260 revolutions per minute (rpm). Additionally, the properties of the ME composite at different temperatures were examined. In the temperature range from −70 °C to 160 °C, the ME coefficients exhibit good regularity and stability, with the measured trend closely matching the simulation results, ensuring the reliability and accuracy of the ME tachometer. To verify its practicality, the measurement capability of the ME tachometer was comprehensively tested under extreme temperature conditions. The results show that in high-temperature environments, the tachometer can accurately measure speed while maintaining a high signal-to-noise ratio (SNR), demonstrating excellent anti-interference ability. The proposed ME tachometer shows promising application potential in extreme temperature conditions, particularly in complex industrial environments that require high reliability and precision. Full article

The n-TiO₂ nanoballs–sticks (TiO₂ NBSs) were successfully deposited on p-lightly boron-doped diamond (LBDD) substrates by the hydrothermal method. The temperature-dependent optoelectronic properties and carrier transport behavior of the n-TiO₂ NBS/p-LBDD heterojunction were investigated. The photoluminescence (PL) of the heterojunction detected four distinct emission peaks at 402 nm, 410 nm, 429 nm, and 456 nm that have the potential to be applied in white-green light-emitting devices. The results of the I-V characteristic of the heterojunction exhibited excellent rectification characteristics and good thermal stability at all temperatures (RT-200 °C). The forward bias current increases gradually with the increase in external temperature. The temperature of 150 °C is ideal for the heterojunction to exhibit the best electrical performance with minimum turn-on voltage (0.4 V), the highest forward bias current (0.295 A ± 0.103 mA), and the largest rectification ratio (16.39 ± 0.005). It is transformed into a backward diode at 200 °C, which is attributed to a large number of carriers tunneling from the valence band (VB) of TiO₂ to the conduction band (CB) of LBDD, forming an obvious reverse rectification effect. The carrier tunneling mechanism at different temperatures and voltages is analyzed in detail based on the schematic energy band structure and semiconductor theoretical model. Full article

NiO_x is a p-type semiconductor with excellent stability, which makes it interesting for a wide range of applications. Broadband photodetectors with high responsivity (R) were fabricated by depositing r.f.-sputtered NiO_x layers on n-Si at room temperature (RT), 50 °C and 100 °C. In self-powered mode the RT diodes have R between 0.95 and 0.39 A/W for wavelengths between 365 and 635 nm, while at a reverse bias of −4 V, the responsivity increases to values between 22 A/W and 10.7 A/W for wavelengths in the same range. The increase of the deposition temperature leads to a decrease of R but also to a smaller reverse dark current. Thus, the 100 °C photodiodes might be more appropriate for applications where high responsivity is required, because of their smaller power consumption compared to the RT diodes. In addition, it was found that the increase of the deposition temperature leads to an increase of the diodes’ series resistance and the resistivity of NiO_x. The effect of Rapid Thermal Annealing (RTA) on the properties of the photodiodes was studied. Annealing at 550 °C for 6 min leads to much higher responsivity compared to R of diodes with as-deposited NiO_x. However, a disadvantage of the annealed diode is that the reverse current depends on the amplitude and polarity of previously applied bias voltage. The higher responsivity of the RTA photodiodes makes them useful as light sensors. Full article

The development and calibration of a measurement system designed for assessing the performance of the avalanche photodiodes (APDs) used in the Compton scattering polarimeter of the CUSP project is discussed in this work. The designed system is able to characterize the APD gain $G_{APD}$ and energy resolution across a wide range of temperatures T (from −20 °C to +60 °C) and bias voltages $V_{bias}$ (from 260 V to 410 V). The primary goal was to experimentally determine the $G_{APD}$ dependence on the T and $V_{bias}$ in order to establish a strategy for stabilizing $G_{APD}$ by compensating for T fluctuations, acting on $V_{bias}$. The results demonstrate the system capability to accurately characterize APD behavior and develop feedback mechanisms to ensure its stable operation. This work provides a robust framework for calibrating APDs for space environments. It is essential for the successful implementation of spaceborne polarimeters such as the Compton scattering polarimeter foreseen aboard the CUbeSat Solar Polarimeter (CUSP) mission under development to perform solar flare X-ray polarimetry. Full article