Oxide Semiconductor Research Articles

CMOS Logic and Capacitorless DRAM by Stacked Oxide Semiconductor and Poly-Si Transistors for Monolithic 3-D Integration

CMOS Logic and Capacitorless DRAM by Stacked Oxide Semiconductor and Poly-Si Transistors for Monolithic 3-D Integration

Inhibiting the imprint effect of the TiN/HZO/TiN ferroelectric capacitor by introducing a protective HfO2 layer

Interfacial differences between the Hf0.5Zr0.5O2 (HZO) and the top/bottom electrodes caused by the process sequence could lead to the imprint effect of the TiN/HZO/TiN ferroelectric capacitor, which leads to serious reliability problems. In this article, a method of introducing a HfO2 protective layer is proposed to inhibit the imprint effect of the TiN/HZO/TiN ferroelectric capacitor. By introducing the HfO2 protective layer, the leakage current at the positive electric field is reduced by three orders of magnitude, the asymmetry of the coercive field is reduced from 1.5 to 0.1 MV/cm, and the endurance is improved by two orders of magnitude with no degradation in retention. The proposed method provides a feasible strategy to inhibit the imprint effect of TiN/HZO/TiN ferroelectric capacitors and is more compatible with complementary metal–oxide–semiconductor processes.

Automatic Learning Rate Adaption for Memristive Deep Learning Systems.

As a possible device to further enhance the performance of the hybrid complementary metal oxide semiconductor (CMOS) technology in the hardware, the memristor has attracted widespread attention in implementing efficient and compact deep learning (DL) systems. In this study, an automatic learning rate tuning method for memristive DL systems is presented. Memristive devices are utilized to adjust the adaptive learning rate in deep neural networks (DNNs). The speed of the learning rate adaptation process is fast at first and then becomes slow, which consist of the memristance or conductance adjustment process of the memristors. As a result, no manual tuning of learning rates is required in the adaptive back propagation (BP) algorithm. While cycle-to-cycle and device-to-device variations could be a significant issue in memristive DL systems, the proposed method appears robust to noisy gradients, various architectures, and different datasets. Moreover, fuzzy control methods for adaptive learning are presented for pattern recognition, such that the over-fitting issue can be well addressed. To our best knowledge, this is the first memristive DL system using an adaptive learning rate for image recognition. Another highlight of the presented memristive adaptive DL system is that quantized neural network architecture is utilized, and there is therefore a significant increase in the training efficiency, without the loss of testing accuracy.

Research on single event effects and hardening design of LDMOS transistors

In this paper, an N-type Lateral Diffused Metal Oxide Semiconductor (LDMOS) device was designed using a heavily doped P+ well and drain N-type buffer layer structure in the BCD process. The hardened mechanism of heavily doped P+ well and drain N-type buffer layer structures was simulated and analyzed using a TCAD device simulator. To verify the anti-SEE performance of the LDMOS, the irradiation test was conducted using Ta ion (LET = 79.2 MeV·cm−2 mg−1). The results show that increasing P+ well doping concentration and using buffer layer structure can increase the single event burnout (SEB) voltage of high-voltage LDMOS devices. SEB did not occur within the full operation voltage range.

Photocatalytic properties of ZnO semiconductor nanoparticles green synthesized employing Ipomoea stans leave extracts

One of the biggest problems in the ecosystem is wastewater contaminated with industrial dyes. These pollutants have a very stable chemical structure, which causes complicated removal. However, a possible alternative for wastewater treatment is zinc oxide semiconductor nanoparticles (ZnO NPs). The approach of this study was the implementation of a green synthesis methodology for the obtention of ZnO nanoparticles employing Ipomoea stans (TV) leaves as extracts. The properties of the ZnO nanoparticles synthesized at 1 %, 2 %, and 4 % w/v (weight/volume) concentration of the extract were obtained from the characterization using different techniques. The FTIR analysis determined the presence of the active functional groups attached to the surface, which capped and stabilized the ZnO NPs; a band located in the range of 500-390 cm−1 confirms the presence of the Zn–O bond. The UV absorption spectra of all ZnO NPs samples were determined by executing the ultraviolet–visible spectroscopy technique, with a characteristic signal located at ∼370 nm and energy gap values between 3.036 eV and 3.101 eV. In addition, XRD patterns determined the average crystallite sizes to be 30.78 nm for ZnO-TV 1 %, 18.68 nm ZnO-TV 2 %, and 11.96 nm ZnO-TV 4 %, respectively. Furthermore, the results from transmission electron microscopy (TEM) displayed the following values of mean particle size of 21 nm, 24.4 nm, and 10.16 nm for ZnO-TV 1 %, ZnO-TV 2 % and ZnO-TV 4 % with S.D. 9.10, 12.5 and 3.6. Finally, the photocatalytic activity was evaluated utilizing the industrial dyes Methyl Orange, Methylene Blue, Rhodamine B, Malachite Green, and Congo Red. Obtaining outstanding results in the degradation of all industrial dyes. All syntheses achieved degradation greater than 91 % for methyl orange, methylene blue, and rhodamine B.

Controlling Oxygen Vacancy Content by Varying Calcination Temperature to Enhance the Gas Sensing Performance of BiVO4 Material

Compared to gas sensors based on single metal oxide, gas sensors based on binary metal oxide semiconductors (MOS) offer a rich variety of structural types and hold great potential for excellent selectivity. Inspired by this, we synthesized BiVO4 powder through a stepwise reaction combining calcination with hydrothermal bath and investigated the influence of different calcination temperatures on its gas sensitivity performance. Our study revealed that BiVO4-600 exhibited optimal TEA gas sensing behavior at 225 °C, showing high response values (Ra/Rg = 43.4) and fast response/recovery times (15 s/52 s). Additionally, the sensor displayed high stability, repeatability, and exceptional selectivity. Preliminary research indicates that calcination temperature induces changes in the oxygen vacancy content of BiVO4, thus affecting its sensing performance.

Analysis of an operational trans-conductance amplifier with positive feedback

In this paper, we present an analysis of an operational trans-conductance amplifier (OTA) with two positive feedback. The direct current (DC) transfer function is obtained by analyzing the OTA using the drain current in the weak inversion region. The analysis results were verified through comparison with SPICE simulations, and the characteristics of the DC transfer function analysis for the OTA design are well matched with the simulation results. The designed OTA dissipates a low power of 41.4 nW, and features the slew rate is improved by 436% compared to a conventional OTA without two positive feedback. Additionally, a DC gain and a unity-gain bandwidth is improved by 36 dB and 6.7 times, respectively. The OTAs are designed for the 0.18 μm complementary metal–oxide–semiconductor (CMOS) process.

Novel β-CdSnO3-SnO2 nanorod-like heterostructure materials for enhancing n-butanol sensing

n-butanol detection is crucial to environmental protection and mankind’s health because of its toxicity and irritation to the respiratory system. Mono-metal oxide semiconductors (such as SnO2) often face disadvantages such as low sensitivity, insufficient selectivity, and a high detection limit. Constructing heterojunctions has been considered an efficient way to enhance the performance of MOS gas sensors. This work presents the synthesis of a series of β-CdSnO3-SnO2 nanorod-like heterostructures with good n-butanol sensitivity using a hydrothermal and post-calcination approach. The optimized CSO/SO-8 shows the highest response value about 90–100 ppm n-butanol at 190 °C, which is 15 times greater than that of SnO2, and 6.5 times more than that of β-CdSnO3. Meanwhile, the CSO/SO-8 also exhibits a short response and recovery time (1–2 s/63 s). More importantly, the detection limit is reduced to ppb level (50 ppb). The improved gas-sensitive properties can be explained by the formation of n-n heterojunctions between β-CdSnO3 and SnO2, which increases the content of chemisorbed oxygen, thus enhancing the performance of the gas-sensitive. Our work not only provides a material with n-n heterostructures but also the strategy for constructing heterojunctions to improve gas-sensitive properties.

Numerical investigation of diamond complementary logic integrated circuits

Silicon complementary metal oxide semiconductor (CMOS) technology drives the integrated circuit industry due to its energy efficiency. The narrow bandgap of silicon has led to the development of wide bandgap semiconductor materials, such as diamond, favored in power electronics, radiofrequency and extreme environment applications. Here we have established a model of the diamond CMOS logic inverter for the first time and successfully simulated the static and dynamic characteristics. The simulated physical model and relevant model parameters are well calibrated with experimental data of diamond p-FET in the literature. The simulation results demonstrate that the all-diamond CMOS inverters possess rail-to-rail operation and excellent inversion characteristics, with the peak gain of 83 V/V, the transition region of 0.25 V, and the noise margins for low and high level of 2.44 V and 2.26 V under VDD = 5 V. Particularly, all-diamond CMOS inverters have improved performance compared to the diamond-GaN inverters, operating at 500 °C with well-preserved inversion characteristics. This thermal reliability indicates that diamond CMOS inverters can be better monolithically integrated for applications in high-temperature environments in the future.

Lorentz Force-Actuated Bidirectional Nanoelectromechanical Switch with an Ultralow Operation Voltage.

The high operating voltage of conventional nanoelectromechanical switches, typically tens of volts, is much higher than the driving voltage of the complementary metal oxide semiconductor integrated circuit (∼1 V). Though the operating voltage can be reduced by adopting a narrow air gap, down to several nanometers, this leads to formidable manufacturing challenges and occasionally irreversible switch failures due to the surface adhesive force. Here, we demonstrate a new nanowire-morphed nanoelectromechanical (NW-NEM) switch structure with ultralow operation voltages. In contrast to conventional nanoelectromechanical switches actuated by unidirectional electrostatic attraction, the NW-NEM switch is bidirectionally driven by Lorentz force to allow the use of a large air gap for excellent electrical isolation, while achieving a record-low driving voltage of <0.2 V. Furthermore, the introduction of the Lorentz force allows the NW-NEM switch to effectively overcome the adhesion force to recover to the turn-off state.

Localized Surface Plasmon Resonances of AgAl Alloy Nanoparticles Self-Organized by Annealing of Ag/Al Bilayer Films

Plasmonic applications have traditionally relied on noble metals such as gold (Au) and silver (Ag) for their excellent plasmonic performance in the visible and near-infrared spectrum. However, these metals are costly, scarce, and have limitations such as low stability (Ag) and interband transition losses, which restrict their spectral range. To address these issues, alternative plasmonic materials have been explored. One such material is aluminum (Al), which is inexpensive, abundant, and exhibits remarkable plasmonic properties in the UV region as well as wide tunability. Al is also compatible with complementary metal–oxide semiconductor (CMOS) fabrication processes and is very stable due to its ultrathin native oxide layer. Alloying different metals can combine their advantageous properties, resulting in enhanced tunable optical characteristics. This study investigates the LSPR properties of AgAl alloy nanoparticles grown after the annealing of precursor AgAl bilayer films. Interestingly, LSPRs were also observed in some cases for the as-deposited bilayers. The experimental results were complemented with simulations conducted via the rigorous coupled-wave analysis (RCWA) method. The investigated materials could be potentially useful for applications in energy harvesting or color printing.

Dynamic Power Saving for CMOS Circuits

With more functionalities being integrated into a microchip today, higher processing power is drawn. As a result of this, clock and logic power consumption has turned out to be a critical issue to be coped with by chip designers. In this paper, we present various power-saving approaches employed in complementary metal oxide semiconductor (CMOS) circuit designs. The approaches involve restructuring the logic circuits, performing clock gating, and selecting the appropriate circuits for counters and frequency divisions. In order to show their efficacies in power optimization, the approaches were applied to a phase-locked loop (PLL), clock divider (CD), full adder (FA), counter, arithmetic logic unit (ALU), and microprocessor without interlocked pipelined stages (MIPS) circuits and validated using Intel Quartus Prime Lite and Mentor Graphics Modelsim. The following conclusions can be drawn from the results: Firstly, the efficacy of minimizing power dissipation using logic restructuring is found to be in direct proportion with the rate of the switching activity (SA); secondly, a maximum of 3.5% of thermal power dissipation can be saved using clock gating; thirdly, gray counters give the lowest power consumption; and, finally, the thermal power estimation for the phase-locked loop (PLL) is relatively higher than that for the clock divider (CD) when both of them are implemented for dividing frequencies.

ZnO nanowires decorated with Pt nanoclusters for selective detection of ppb-level nitrogen dioxide

Noble metal loading is an efficient way to improve the sensing performance of metal oxide semiconductor (MOS) gas sensors. In this work, platinum (Pt) nanoclusters loaded ZnO nanowires (Ptc-ZnO) were used to fabricate a NO2 sensor. Pure ZnO nanowires were prepared by a solvothermal method and Pt nanoclusters were loaded via a sacrificial templating route. The Ptc-ZnO based sensor with a trace of Pt loading (0.17 wt%) shows a high response to ppb-level NO2 (26.1–100 ppb), 4.4 times higher than that of pure ZnO. Additionally, it also exhibits excellent selectivity, low theoretical limit of detection (1.19 ppb) and good stability to humidity. The enhancing mechanism on gas sensing performance by Pt loading was discussed and investigated via HAADF-STEM, XPS, NO2-TPD and other methods. This work provides a way to develop gas sensor for ultralow NO2 concentration real-time detection.

Unraveling the Chicken Meat Volatilome with Nanostructured Sensors: Impact of Live and Dehydrated Insect Larvae Feeding.

Incorporating insect meals into poultry diets has emerged as a sustainable alternative to conventional feed sources, offering nutritional, welfare benefits, and environmental advantages. This study aims to monitor and compare volatile compounds emitted from raw poultry carcasses and subsequently from cooked chicken pieces from animals fed with different diets, including the utilization of insect-based feed ingredients. Alongside the use of traditional analytical techniques, like solid-phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS), to explore the changes in VOC emissions, we investigate the potential of S3+ technology. This small device, which uses an array of six metal oxide semiconductor gas sensors (MOXs), can differentiate poultry products based on their volatile profiles. By testing MOX sensors in this context, we can develop a portable, cheap, rapid, non-invasive, and non-destructive method for assessing food quality and safety. Indeed, understanding changes in volatile compounds is crucial to assessing control measures in poultry production along the entire supply chain, from the field to the fork. Linear discriminant analysis (LDA) was applied using MOX sensor readings as predictor variables and different gas classes as target variables, successfully discriminating the various samples based on their total volatile profiles. By optimizing feed composition and monitoring volatile compounds, poultry producers can enhance both the sustainability and safety of poultry production systems, contributing to a more efficient and environmentally friendly poultry industry.

An octave tuning range quad-core VCO using a multi-mode resonator

This paper presents a novel multi-core multi-mode electric-magnetic (E-M) mixed-coupling voltage-controlled oscillator (VCO), achieving wide tuning range and phase noise optimization simultaneously through a multi-core structure. A symmetric multi-mode resonator is proposed to address the issue of differential signal mismatch caused by transformer asymmetry. An inductor ring is used to balance the inductance of each mode and its effect in each mode is analyzed in detail. A symmetrical switch network is employed for mode switching, offering advantages such as reduced parasitics and mismatch. The utilization of a varactor combined with a fixed capacitor enables electrical coupling, ensuring overlapping frequency bands even with variations in process, voltage, and temperature (PVT), and extending the tuning range. Furthermore, a switched resistor array is employed to bias the negative resistance pair and minimize the contribution of 1/f noise upconversion to the phase noise. Designed in a 40-nm complementary metal–oxide–semiconductor (CMOS) technology with a core area of 0.16 mm2, the VCO achieves a simulated continuous tuning range of 81.5%, spanning from 11.1 to 26.4 GHz. Operating at a 1.1 V supply with a power consumption of 16 mW, the phase noise at 12.15 GHz is −118.6 dBc/Hz at a 1 MHz offset, corresponding to a figure-of-merit (FoM) of 188.3 dBc/Hz and a FoMT of −206.3 dBc/Hz.

Comprehensive study on the physical properties of CuO-ZnO thin films: Insights into solar cell simulation

Metal oxide semiconductors have long been utilized in various optoelectronic applications, including solar cells, photocatalysis, and Schottky diodes. However, these materials often encounter challenges, prompting the exploration of alternative thin-film structures composed of non-toxic and cost-effective materials. One such promising system is the Coupled Oxide Systems (COS), exemplified by CuO-ZnO (CZO). Despite the potential of COS, comprehensive studies on their synthesis and optimization remain limited. Here, we investigate the physical and optical properties of CZO thin films, confirming successful synthesis and highlighting their potential as alternatives to conventional materials like CIGS and CdTe. In the second part, we explore a novel solar cell structure, FTO/ZnO/X/CuO-ZnO/Mo, with various buffer layer options (CdS, ZnS, Zn0.38Ge0.62O, SnS2, and [Al0.025Ga0.975]2O3). Our results reveal that the solar cell with CdS as the buffer layer exhibits the highest efficiency. This work not only summarizes the fundamental principles governing the optoelectronic properties of materials but also elucidates critical strategies for fabricating high-efficiency solar cells. Furthermore, we have conducted a comparative analysis involving 70 different solar cell structures. Additionally, we discuss potential strategies for the next generation of solar cells to further enhance power conversion efficiency (PCE).

Advancements and challenges in strained group-IV-based optoelectronic materials stressed by ion beam treatment

In this perspective article, we discuss the application of ion implantation to manipulate strain (by either neutralizing or inducing compressive or tensile states) in suspended thin films. Emphasizing the pressing need for a high-mobility silicon-compatible transistor or a direct bandgap group-IV semiconductor that is compatible with complementary metal–oxide–semiconductor technology, we underscore the distinctive features of different methods of ion beam-induced alteration of material morphology. The article examines the precautions needed during experimental procedures and data analysis and explores routes for potential scalable adoption by the semiconductor industry. Finally, we briefly discuss how this highly controllable strain-inducing technique can facilitate enhanced manipulation of impurity-based spin quantum bits (qubits).

Toward rationally designing high-performance perovskite sensing material: Role of dielectric constant and crystal symmetry

P-type oxide semiconductor gas sensors have gained increasing attention for their distinctive catalytic activity, high oxygen adsorption, and high humidity resistance. However, the low gas response of p-type sensors restricts their utilization, prompting numerous attempts to overcome this limitation. In this study, we have successfully engineered a promising p-type gas sensor by increasing the dielectric constant and optimizing crystal symmetry, departing from conventional approaches such as reducing particle size, constructing complex heterojunctions, and decorating with noble metals. The as-prepared multiferroic Bi0.92Dy0.8FeO3 gas sensor exhibits a well-defined gas response to acetone, demonstrating ultralow detection limits, distinctive selectivity, high humidity resistance, and long-term stability. Through comparisons of crystal symmetry, morphology, specific surface area, atomic chemical environment, dielectric properties, and sensing properties among a series of Dy3+ doped BiFeO3 solid solutions, we attribute this extraordinary sensing performance of Bi0.92Dy0.8FeO3 to its higher dielectric constant and unique domain-wall structure arising from its non-centrosymmetric crystal structure. This work provides additional perspective for preparing high-performance gas sensors.

Enhancing SERS sensitivity of semiconductors through constructing CuO@TiO2 heterojunctions via atomic layer deposition

Semiconductors hold great promise for surface-enhanced Raman scattering (SERS) applications. Various strategies have been proposed to address the challenge of low SERS sensitivity in semiconductors, with the construction of heterojunctions being among the most effective approaches. In this study, CuO@TiO2 heterojunctions were fabricated by depositing a precisely controlled layer of TiO2 film onto the surface of CuO nanowires (CuO NWs) using the atomic layer deposition (ALD) technique. This approach significantly enhances the SERS sensitivity of CuO NWs, and the SERS performance of the semiconductor heterojunction can be further optimized by accurately adjusting the thickness of TiO2. The SERS activity exhibits systematic variations with the TiO2 thickness across the CuO@TiO2-Rhodamine 6G (R6G) system, with the optimal SERS performance of the heterojunction substrate achieved at a TiO2 thickness of 250 cycles. This finding highlights the substantial influence of TiO2 coating thickness on the photo-induced charge transfer (PICT) processes within the CuO@TiO2-R6G system. Furthermore, CuO@TiO2 heterojunctions demonstrate exceptional stability and uniformity. As a result, this study holds significant importance in enhancing the SERS performance of oxide semiconductors, designing optimal semiconductor heterojunction SERS substrates, and investigating thickness-dependent charge transfer mechanisms in semiconductors.

Computational design and evaluation of a quad-MOSFET device for quality control of therapeutic accelerator-based neutron beams

Accurate real-time monitoring of neutron beams and distinguishing between thermal, epithermal and fast neutron components in the presence of a photon background is crucial for the effectiveness of accelerator-based boron neutron capture therapy (AB-BNCT). In this work, we propose an innovative quadruple metal–oxide–semiconductor field-effect transistor (MOSFET) device for real-time, cost-effective beam quality control; one detector is kept uncovered while the other three are covered with either a B4C, cadmium and B4C or polyethylene converter.Individual MOSFET converter configurations were optimised via Monte Carlo simulations to maximise signal selectivity across neutron energy spectra. Results demonstrate the quad-MOSFET device’s efficacy in quantifying changes in neutron flux, underscoring its potential as a useful instrument in the AB-BNCT quality control process.