Simple Semiconductor Research Articles

Synthesis of novel Fe-BiOCl based nanosheets assembled rod (FBC-NSR)-based photoactive materials: an effective photodegradation of antibiotics

Fe-incorporated BiOCl-nanosheet assembled rods (FBC-NSR) based photoactive materials were synthesized using a simple sol–gel process to degrade tetracycline (TC) pharmaceuticals compound (PCs) under solar irradiation. The as-prepared FBC-NSR-based photoactive materials were characterized using various characterization techniques including scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), photoluminescent (PL) spectroscopic analysis, and Fourier transform infrared spectroscopy (FT-IR). The structural changes were observed upon doping of Fe metals within the FBC-NSR-based photoactive materials. Intriguingly, the band gap value decreased from ~ 1.81 eV to ~ 1.29 eV with increasing the amount of Fe metals (0.5 g, and 1.0 g) within the FBC-NSR named as FBC-NSR-2 and FBC-NSR-3-based photoactive materials, respectively. The lower band gap value favors the photodegradation of environmental pollution. The synthesized FBC-NSR-3 shows the highest degradation ~ 97% and ~ 72.1% at 1 mg/L and 10 mg/L TC antibiotic, respectively. The photodegradation was higher at pH 10, indicating •OH radicals play a major role in the photodegradation of TC molecules. PL spectra confirm the higher oxygen vacancy, improved transfer of electrons, and separation efficiency of photo-induced electron hole-pairs, thereby high photodegradation efficiency. Therefore, the preparation of FBC-NSR-based photoactive materials is simple, cost-effective, and promising semiconductor materials for the removal of environmental pollution.

Predicting exciton binding energies from ground-state properties

We systematically investigate the correlations between exciton binding energies and various easily calculated ground-state properties (“predictors”) that have been proposed to correlate with them. We do so for 51 bulk compounds, ranging from simple binary semiconductors to more exotic materials such as noble gas solids, perovskites, and layered systems and show that using only a few easily calculable parameters, a broadly applicable clustering of materials according to their exciton binding energies is possible. While no single one of the proposed parameters satisfactorily predicts the exciton binding energy, a combination of several parameters that enter the Wannier-Mott model or characterize the nature of the valence band and the ionicity of the compound allows a reliable automated clustering of exciton binding energies. The results allow an efficient estimation of the importance of excitonic effects without the need for expensive many-body perturbation theory calculations or other advanced numerically demanding approaches. Published by the American Physical Society 2024

Surface structure-based model to calculate thermal and optical properties in nanoscale and quantum dot semiconductors

Surface combination structure was used to design the construction of nano and quantum films, particles, and dots. The created model was applied to tetrahedral semiconductor nanoparticles and quantum dots with a successful performance. It works better than reported experimental data across the whole size range, from the bulk state to the critical size of quantum dots. The model helps to figure out the melting point that changes with the nanosize scale as applied on Si and Sn, which are simple tetrahedral semiconductors, and for CdS and CdSe, which are among II-VI group compounds. It was also used to calculate melting-related parameters such as cohesive energy, Debye temperature, vibrational entropy, and melting enthalpy. The nanosize dependence of the lattice volume and the atom's ionization energy describes the solid surface structure. From the model, an equation was obtained to calculate the energy gaps in Si, CdS, and CdSe particles that are nano- and quantum-dot-sized, and the results are compared to the experimental data that goes with these particles.

Giant nonlinear Hall and wireless rectification effects at room temperature in the elemental semiconductor tellurium

The second-order nonlinear Hall effect (NLHE) in non-centrosymmetric materials has recently drawn intense interest, since its inherent rectification could enable various device applications such as energy harvesting and wireless charging. However, previously reported NLHE systems normally suffer from relatively small Hall voltage outputs and/or low working temperatures. In this study, we report the observation of a pronounced NLHE in tellurium (Te) thin flakes at room temperature. Benefiting from the semiconductor nature of Te, the obtained nonlinear response can be readily enhanced through electrostatic gating, leading to a second-harmonic output at 300 K up to 2.8 mV. By utilizing such a giant NLHE, we further demonstrate the potential of Te as a wireless Hall rectifier within the radiofrequency range, which is manifested by the remarkable and tunable rectification effect also at room temperature. Extrinsic scattering is then revealed to be the dominant mechanism for the NLHE in Te, with symmetry breaking on the surface playing a key role. As a simple elemental semiconductor, Te provides an appealing platform to advance our understanding of nonlinear transport in solids and to develop NLHE-based electronic devices.

1 V Electronically Tunable Differential Difference Current Conveyors Using Multiple-Input Operational Transconductance Amplifiers.

This paper presents electronically tunable current conveyors using low-voltage, low-power, multiple-input operational transconductance amplifiers (MI-OTAs). The MI-OTA is realized using the multiple-input bulk-driven Metal Oxide Semiconductor transistor (MIBD-MOST) technique to achieve minimum power consumption. The MI-OTA also features high linearity, a wide input range, and a simple Complementary Metal Oxide Semiconductor (CMOS). Thus, high-performance electronically tunable current conveyors are obtained. With the MI-OTA-based current conveyor, both an electronically tunable differential difference current conveyor (EDDCC) and a second-generation electronically tunable current conveyor (ECCII) are available. Unlike the conventional differential difference current conveyor (DDCC) and second-generation current conveyor (CCII), the current gains of the EDDCC and ECCII can be controlled by adjusting the transconductance ratio of the current conveyors. The proposed EDDCC has been used to realize a voltage-to-current converter and current-mode universal filter to show the advantages of the current gain of the EDDCC. The proposed current conveyors and their applications are designed and simulated in the Cadence environment using 0.18 μm TSMC (Taiwan Semiconductor Manufacturing Company) CMOS technology. The proposed circuit uses ±0.5 V of power supply and consumes 90 μW of power. The simulation results are presented and confirm the functionality of the proposed circuit and the filter application. Furthermore, the experimental measurement of the EDDCC implemented in the form of a breadboard connection using a commercially available LM13700 device is presented.

Tailoring second harmonic emission by ZnO nanostructures: Enhancement of directionality

Tailoring nonlinear optical properties at the nanoscale is a hot topic in nowadays nanophotonics, promising for applications spanning from sensing to ultrafast optical communications. Here we present a numerical approach of designing a simple semiconductor nanostructure able to tailor second harmonic emission in the near- and far-field. We start from linear simulations of ZnO nanospheres, which reveal multipolar nature of the scattering. Next, we show how the same nanospheres, with radii in 30–130 nm range, excited at 800 nm, manipulate the directivity of the emitted second harmonic. We observe that the nanospheres which exhibit Kerker condition at 400 nm, emit the second harmonic field in the forward direction. We further investigate how the asymmetry (ellipsoid geometry) tailors the second harmonic directivity. We finally introduce geometry with low chiro-optical response, and observe that the second harmonic far-field depends on the handedness of the light exciting the nanostructure at 800 nm.

Conductance modification of molybdenum oxide thin films through oxygen-vacancy engineering for visible-blind ultraviolet photodetection

We propose a simple approach to locally modify the conductance of molybdenum oxide thin films with thermal annealing in oxygen atmosphere at relatively low temperature for constructing a visible-blind ultraviolet photoconductor. The amorphous MoO x is grown by remote plasma enhanced atomic layer deposition (RPALD), and then crystallized into α-MoO x at 500 °C in argon atmosphere, which exhibits good conductance with resistivity of 3.9 × 10−3 Ω cm due to the formation of oxygen vacancies. Good ohmic contact between Ti and the crystallized MoO x is demonstrated with specific contact resistance of 9.74 × 10−4 Ω cm2. The lateral Au/Ti-MoO x -Ti/Au structures are defined and the conductance of the exposed MoO x channel is significantly modified by thermal annealing in oxygen atmosphere to form a photodetector, which shows obvious photoresponse at the wavelength of less than 372 nm with low dark current of 0.9 pA at 5 V, and the remarkable responsivity of 0.75 mA W−1 at 280 nm is achieved with a high ultravoilet/visible rejection ratio. The low dark current and incredible responsivity can be attributed to the good ohmic contacts of untreated MoO x and the reduction of number of oxygen vacancies in the MoO x channel. The key role of oxygen vacancy on the conductance of MoO x has been demonstrated. Those results suggest that the MoO x thin films are promising candidate for visible-blind ultraviolet photodetectors in a simple complementary metal oxide semiconductor (CMOS)-compatible process.

Demonstration of the feasibility and practical value of direct acoustic measurements in liquid metals

The temperature dependences of ultrasound absorption and propagation speed in simple semimetals, semiconductors, and semiconductor compounds have been studied in this article. Experimental and theoretical results testify to the microheterogeneity of semimetals and semiconductor melts. Generalization and analysis of experimental data on the absorption and propagation speed of ultrasound in melts based on D.I. Mendeleev periodic law clearly indicate the presence of micro-groups of atoms (clusters) in them, microheterogenizing melts of semimetals and semiconductors. The urgency of this problem is predetermined by the problem of the liquid state of matter. The dependence of ultrasound absorption and propagation speed on temperature is measured using several groups of samples in paper, each group is heated to a different temperature. It is proved that melts have clustered in their atomic matrix, and so melts with semiconductor properties are micro-inhomogeneous. These results are needed to scale melt sonication to an industrial scale and are needed to provide valuable new insights into temperature dependencies of ultrasound absorption.

Visible Light‐Driven Photocatalytic Transformation of Thiols to Disulfides in Water Catalyzed by Bi2S3

Selective coupling of thiols to produce disulfides is one very important and classic type of coupling reactions. Herein, an environmentally friendly and practical photocatalytic system for oxidative coupling of thiols to disulfides is developed. With no sacrificial agent, no additional additive, just sole water as solvent, performed in air at room temperature, excellent conversions of thiols and excellent selectivities of disulfides are obtained using a cheap and simple semiconductor material of bismuth sulfide (Bi2S3) under blue LED illumination. Excellent conversions and selectivities for coupling of thiols to produce disulfides are obtained, and the system is reusable. The as‐prepared photocatalyst is adequately characterized and the mechanism of photocatalytic reaction is discussed deeply.

Development of Pyr‐TPA as Interfacial Passivation Layer Enabling Efficient and Stable n–i–p Perovskite Solar Cells

Interfacial passivation is a crucial technique for improving the performance of perovskite solar cells (PSCs) by suppressing nonradiative recombination. Incorporating electron‐rich functional groups into organic semiconductors can combine the advantages of Lewis bases and organic semiconductors to achieve defect passivation of perovskite films and interfacial charge transport improvement simultaneously. However, interlayers generated by organic semiconductors are often destroyed during the deposition of the hole transport layer (HTL) in n–i–p PSCs. This prevents the accurate evaluation of interfacial passivation effects. Herein, a pyromellitic derivative, 2,6‐bis(4‐(bis(4‐methoxyphenyl)amino)phenyl)pyrrolo[3,4‐f]isoindole‐1,3,5,7(2 H,6 H)‐tetraone (Pyr‐TPA), containing four carbonyl groups that can passivate defects and enhance hole transport while simultaneously acting as a stable interlayer at the perovskite/HTL interface due to its ideal solubility profile is introduced. As a result, Pyr‐TPA as an interlayer can minimize nonradiative recombination loss, resulting in a power conversion efficiency of up to 24.16%. Additionally, the interfacial Pyr‐TPA passivation layer also exhibits strong resistance to moisture and ion migration, leading to enhanced long‐term ambient stability of PSCs based on this material. Findings provide valuable insights into developing efficient and stable PSCs with simple and effective organic semiconductor interfacial passivation materials.

Semiconductor Gas Sensors for Detecting Chemical Warfare Agents and Their Simulants

On-site detection of chemical warfare agents (CWAs) can be performed by various analytical techniques. Devices using well-established techniques such as ion mobility spectrometry, flame photometry, infrared and Raman spectroscopy or mass spectrometry (usually combined with gas chromatography) are quite complex and expensive to purchase and operate. For this reason, other solutions based on analytical techniques well suited to portable devices are still being sought. Analyzers based on simple semiconductor sensors may be a potential alternative to the currently used CWA field detectors. In sensors of this type, the conductivity of the semiconductor layer changes upon interaction with the analyte. Metal oxides (both in the form of polycrystalline powders and various nanostructures), organic semiconductors, carbon nanostructures, silicon and various composites that are a combination of these materials are used as a semiconductor material. The selectivity of a single oxide sensor can be adjusted to specific analytes within certain limits by using the appropriate semiconductor material and sensitizers. This review presents the current state of knowledge and achievements in the field of semiconductor sensors for CWA detection. The article describes the principles of operation of semiconductor sensors, discusses individual solutions used for CWA detection present in the scientific literature and makes a critical comparison of them. The prospects for the development and practical application of this analytical technique in CWA field analysis are also discussed.

Forecasting the chaotic dynamics of external cavity semiconductor lasers.

Chaotic time series prediction has been paid intense attention in recent years due to its important applications. Herein, we present a single-node photonic reservoir computing approach to forecasting the chaotic behavior of external cavity semiconductor lasers using only observed data. In the reservoir, we employ a semiconductor laser with delay as the sole nonlinear physical node. By investigating the effect of the reservoir meta-parameters on the prediction performance, we numerically demonstrate that there exists an optimal meta-parameter space for forecasting optical-feedback-induced chaos. Simulation results demonstrate that using our method, the upcoming chaotic time series can be continuously predicted for a time period in excess of 2 ns with a normalized mean squared error lower than 0.1. This proposed method only utilizes simple nonlinear semiconductor lasers and thus offers a hardware-friendly approach for complex chaos prediction. In addition, this work may provide a roadmap for the meta-parameter selection of a delay-based photonic reservoir to obtain optimal prediction performance.

Accurate thermochemistry of covalent and ionic solids from spin-component-scaled MP2.

We study the performance of spin-component-scaled second-order Møller-Plesset perturbation theory (SCS-MP2) for the prediction of the lattice constant, bulk modulus, and cohesive energy of 12 simple, three-dimensional covalent and ionic semiconductors and insulators. We find that SCS-MP2 and the simpler scaled opposite-spin MP2 (SOS-MP2) yield predictions that are significantly improved over the already good performance of MP2. Specifically, when compared to experimental values with zero-point vibrational corrections, SCS-MP2 (SOS-MP2) yields mean absolute errors of 0.015 (0.017) Å for the lattice constant, 3.8 (3.7) GPa for the bulk modulus, and 0.06 (0.08) eV for the cohesive energy, which are smaller than those of leading density functionals by about a factor of two or more. We consider a reparameterization of the spin-scaling parameters and find that the optimal parameters for these solids are very similar to those already in common use in molecular quantum chemistry, suggesting good transferability and reliable future applications to surface chemistry on insulators.

Effects of manganese-doping on the enhanced solar photocatalytic properties of AgBr catalyst: Mechanism and DFT modeling

Manganese ion doping engineering, is promising in the field of photocatalysis, but its effect on simple structure semiconductor is not clear. In this work, high-efficiency manganese doped AgBr photocatalysts were manufactured via an ice bath deposition process and were systematically characterized. Under simulated sunlight irradiation, Mn2+ doped AgBr possessed good degradation activity to rhodamine B (RhB) and Ciprofloxacin (CIP). Notably, the optimal sample AM-2 (the mole ratio of Mn element in the whole sample is 0.014 %) can degrade RhB at a reaction rate constant of 0.10334 min-1, which was 7.72 times that of pure AgBr. In light of density functional theory (DFT), the improvement of photocatalytic performance was due to the incorporation of Mn ions that induced lattice strain, affected the charge distribution, and generated an intermediate Mn 3d-Br 2p two-dimensional energy level in the AgBr band gap. Photoelectrochemical experiments verified that Mn2+ doping promoted the separation and transfer of photogenerated carriers and enhanced light absorption. In addition, the practical application ability of photocatalyst was investigated, and a reliable photocatalytic mechanism was proposed. This study may provide enlightening significance for the general application of doping engineering.

Passive mode-locking and terahertz frequency comb generation in resonant-tunneling-diode oscillator

Optical frequency combs in the terahertz frequency range are long-awaited frequency standards for spectroscopy of molecules and high-speed wireless communications. However, a terahertz frequency comb based on a low-cost, energy-efficient, and room-temperature-operating device remains unavailable especially in the frequency range of 0.1 to 3 THz. In this paper, we show that the resonant-tunneling-diode (RTD) oscillator can be passively mode-locked by optical feedback and generate a terahertz frequency comb. The standard deviation of the spacing between the comb lines, i.e., the repetition frequency, is reduced to less than 420 mHz by applying external bias modulation. A simulation model successfully reproduces the mode-locking behavior by including the nonlinear capacitance of RTD and multiple optical feedback. Since the mode-locked RTD oscillator is a simple semiconductor device that operates at room temperature and covers the frequency range of 0.1 to 2 THz (potentially up to 3 THz), it can be used as a frequency standard for future terahertz sensing and wireless communications.

Balancing the Photo‐Induced Carrier Transport Behavior at Two Semiconductor Interfaces for Dual‐Polarity Photodetection

AbstractThe carrier transport dynamics at the surface/interface of semiconductors determine the electronic and optical properties of devices. Thus, precise control of their dynamic processes while understanding the nature of these characteristics is crucial for modulating device functionalities. Here, a photoelectrochemical‐type photosensor is built using monocrystalline p‐GaN nanowires on the Si platform, which unambiguously exhibits either positive or negative photocurrent upon different light illumination. Such dual‐polarity photocurrents are attributed to photogenerated‐carrier‐transport competition at two interfaces: the GaN/electrolyte and GaN/Si interface. Particularly, a rational Pt decoration successfully accelerates the carrier migration at the GaN/electrolyte interface that breaks the original balance of carrier transport. This mechanism is further elaborated by Kelvin‐probe‐force‐microscopy characterization, which intuitively reveals the impact of Pt decoration on modulating nanowires’ surface band bending and the consequent carrier dynamics at the interfaces. These insights into the control of carrier dynamics shed light on achieving multi‐functional PEC devices built upon simple semiconductor architectures.

Prediction of spin-dependent electronic structures of 3d transition metals doped Hittorf's violet phosphorene towards spintronics

Modulation of spin-dependent properties in semiconductor is of importance in exploring the potential application in spintronics. Here, we theoretically investigated the structural deformation, electronic characters, and magnetic properties of the single-layered Hittorf's violet phosphorene nanosheet with 3 d transition metal atoms (ranging from Sc to Ni) doping and under external electric field. The electronic band structures and magnetic properties was found to be obviously modulated by the dopants: the existence of a large spin splitting of the dopant 3 d states tailors the semiconducting phosphorene into simple magnetic semiconductor or bipolar magnetic semiconductor, except for the case of Sc. The application of an appropriate electric field to V-doped system could induce a transition from bipolar magnetic semiconductor to half metal with the carriers fully spin-polarized in alternative spin channel. Moreover, Hittorf's violet phosphorene-based field-effect transistor was proposed with the aim of realizing gate-voltage control on the carriers' spin orientation. Our findings pointed out the possibilities for realizing spin-dependent field-effect transistor in doped Hittorf's violet phosphorene nanosheet and opened a window for the burgeoning field of multifunctional 2D nanoelectronics and spintronics devices. • Ranging from Ti to Ni dopants can behave (bipolar) magnetic semiconductors. • Sc-doped Hittorfene is a nonmagnetic semiconductor. • The application of the electric field to V-doped Hittorfene can induce half metal transition. • The reversed carriers' spin orientation would be potential for spintronic devices.

Real-Time Nonlinear Behavioral Electrothermal Device-Level Emulation of IGBT on Heterogeneous Adaptive Compute Acceleration Platform

Power converter design evaluation by means of real-time simulation techniques is prevalent, although it is mostly restricted to simple power semiconductor switch models that exclude device-level physical details. In this work, the nonlinear high-order electro-thermal model of the Insulated-gate bipolar transistor (IGBT) is developed and then deployed onto the heterogeneous digital hardware for real-time implementation. As the complexity of the nonlinear behavioral model (NBM) of the IGBT poses a significant computational burden on real-time hardware emulation, machine learning (ML) methodology is utilized so that the trained model can reproduce the characteristics of its original counterpart as much as possible and then it is implemented on the Adaptive Compute Acceleration Platform (ACAP), which composes of the processing system (PS), programmable logic (PL), and Artificial Intelligent Engine (AIE). The vector multiplication feature of the AIE caters to mathematical operations of the ML-based model particularly well and consequently enables it to be executed in real-time with remarkable speedup over the original model with which matrix inversion is otherwise mandatory. Finally, the validation for real-time device-level results and system-level results of a multi-converter system is provided by SaberRD® and MATLAB/Simulink®.

Detection of pH and Urea with an Extended Gate Field-Effect Transistor Based Microsensor

Here, extended gate field-effect transistor-based (EGFET) microsensors have been developed for high sensitive detection of pH and urea. EGFET was made by integrating with a microelectrode. Briefly, the EGFET-based pH microsensor was developed by modifying the surface of a microelectrode with polypyrrole (PPy) via electropolymerization and integrating it with a small, simple and inexpensive metal oxide semiconductor field-effect transistor (MOSFET). As for the EGFET-based urea microsensor, urease enzyme was immobilized in PPy. The measurements of pH and urea were made in solutions at different pH values and urea concentrations, respectively. The results showed that the pH microsensor had a very good sensitivity of 67 mV/pH in a pH range of 5-12. Similarly, the EGFET-based urea microsensor showed a linear response range of 10-9 to 10-5 M urea with sensitivities of 35.5 mV/decade urea and 10 µA/decade urea. The reported EGFET-based pH and urea microsensors have great potential for use in the biomedical field, especially in applications where local analysis is required.

Design and Realization of Ohmic and Schottky Interfaces for Oxide Electronics

Understanding band alignment and charge transfer at complex oxide interfaces is critical to tailoring and utilizing their diverse functionality. Toward this goal, both Ohmic‐ and Schottky‐like charge transfers at oxide/oxide semiconductor/metal interfaces are designed and experimentally validated. A method for predicting band alignment and charge transfer in ABO3 perovskites is utilized, where previously established rules for simple semiconductors fail. The prototypical systems chosen are the rare class of oxide metals, SrBO3 with B = V–Ta, when interfaced with the multifaceted semiconducting oxide, SrTiO3. For B = Nb and Ta, it is confirmed that a large accumulation of charge occurs in SrTiO3 due to the higher energy Nb and Ta states relative to Ti. This gives rise to a high mobility metallic interface, which is an ideal epitaxial oxide/oxide Ohmic contact. On the contrary, for B = V, there is no charge transfer into the SrTiO3 interface, which serves as a highly conductive epitaxial gate metal. Going beyond these specific cases, this work opens the door to integrating the vast phenomena of ABO3 perovskites into a wide range of practical devices.