Single Silicon Research Articles

Revealing the Singlet Fission Mechanism for a Silane-Bridged Thienotetracene Dimer.

Tetraceno[2,3-b]thiophene is regarded as a strong candidate for singlet fission-based solar cell applications due to its mixed characteristics of tetracene and pentacene that balance exothermicity and triplet energy. An electronically weakly coupled tetraceno[2,3-b]thiophene dimer (Et2Si(TIPSTT)2) with a single silicon atom bridge has been synthesized, providing a new platform to investigate the singlet fission mechanism involving the two acene chromophores. We study the excited state dynamics of Et2Si(TIPSTT)2 by monitoring the evolution of multiexciton coupled triplet states, 1TT to 5TT to 3TT to T1 + S0, upon photoexcitation with transient absorption, temperature-dependent transient absorption, and transient/pulsed electron paramagnetic resonance spectroscopies. We find that the photoexcited singlet lifetime is 107 ps, with 90% evolving to form the TT state, and the complicated evolution between the multiexciton states is unraveled, which can be an important reference for future efforts toward tetraceno[2,3-b]thiophene-based singlet fission solar cells.

Quantitative shear stress imaging in high throughput in-line Si wafer inspection

Defect inspection methods are basic steps in electronic chip manufacturing and power device production processes in the semiconductor industry. Based on stress induced photoelastic anisotropy, in-line polarized stress imaging (PSI) and quantitative determination of the local shear stress component are possible in single crystalline silicon wafers. Hereafter, such polarization stress images are compared and validated quantitatively with results of finite element simulations based on different 3D elastic models. Uniquely, high resolution at high throughputs is achieved for 300 mm wafer size in the present quantitative stress imaging study.

Enhanced second harmonic generation from supercavity mode and magnetic resonance in dumbbell-shaped silicon nanoblock

Abstract Electromagnetic multipole resonance can be excited by dielectric nanostructures of appropriate size to effectively promote light-matter interaction. The interactions between light and nanostructures have the capability to enhance the electromagnetic field in the near field, thereby improving the nonlinear effect of nanostructures. We illustrate that the supercavity mode and magnetic dipole resonance are activated by a single dumbbell-shaped silicon nanoblock (DS-SiNB), to trap the near-field electromagnetic field energy. Enhanced second harmonic generation is achieved by exploiting the localized electromagnetic field at the surface of the nanostructure. Numerical simulations reveal that magnetic quadrupole (MQ) and total electric dipole (TED) can be coupled to the same radiation channel by adjusting continuously the aspect ratio Lout/Ly (the outer edge length to the length of DS-SiNB) of the nanoblock. When the aspect ratio Lout/Ly = 1, the supercavity mode formed by the interference of MQ and TED is excited at λ1 = 1124 nm. And, the strong magnetic resonance mode formed by the coupling of two magnetic dipoles (MD) in the same direction is also excited at λ2 = 1124 nm. Supercavity mode and strong magnetic dipole resonance can effectively capture electromagnetic fields on the surface of nanostructures to attain enhanced second harmonic generation (SHG). Our study presents a novel approach to enhance the nonlinear optical effect of a single silicon nanostructure, which can lead to the development of more efficient nonlinear optical devices.

SiO Enabled by ZSM‐5 and Graphene as Long‐Cycle and High‐Rate Anodes for Lithium‐Ion Batteries

AbstractSilicon oxides (SiO, SiO2) with high theoretical capacity and low cost are viewed as promising anodes for the next‐generation lithium‐ion batteries (LIBs) but suffer from inferior rate capability and coulombic efficiency (CE) owing to the sluggish charge transfer kinetics. Herein, the study proposes a multichannel modulation strategy induced by ZSM‐5 and SiO as well as electron‐rich graphene to effectively solve the above issue. Specially, the ZSM‐5, which can not only provide a certain Li+ reserve capacity as an anode material, but also serve as a bridge to connect the isolated SiO nanoparticles, providing Li+ transport channel and adjusting the transfer kinetic, making it to achieve two things at one stroke, so that the as‐obtained SiO@ZSM@Gra composite shows improved rate performance and CE compared to that of single silicon oxides. Combing with the CV and EIS fitting analysis, it is demonstrated that the constructed composites own higher Li+ diffusion coefficient and more charge conduction capability. Furthermore, the fabricated full cell with LiNi0.8Co0.1Mn0.1O2 exhibits good electro‐chemical properties. The proposed strategy for intrinsic accelerating charge transfer can be conductive to electrode design for the next‐generation low cost and high energy LIBs.

A compact scintillator-based detector for high energy neutron spectrometry

A compact neutron spectrometer consisting of a 6 mm × 6 mm × 120 mm prism of EJ-276 plastic scintillator capable of pulse shape discrimination coupled to a single silicon photomultiplier is described. In principle this device will be capable of spectroscopic measurements exceeding 100 MeV using unfolding analyses with detector response functions measured at neutron time-of-flight facilities. A characterisation of the device is described and illustrated with measurements of the detector response made at three fast neutron facilities with energies between 5.0 MeV and 63.5 MeV. Nearly mono-energetic detector response functions were used to produce neutron energy spectra by unfolding light output distributions measured with the detector in the energy range of interest.

All-Optical XOR, AND, OR, NOT, NOR, NAND, and XNOR Logic Operations Based on M-Shaped Silicon Waveguides at 1.55 μm.

Silicon waveguides are essential to integrated photonics, which is where optical and electronic components are coupled together on a single silicon chip. These waveguides allow for the integration of signal processing and optical transmission, which advances data centers, telecommunications, and other optical applications. Thus, our study involves the simulation of essential all-optical logic operations, namely XOR, AND, OR, NOT, NOR, NAND, and XNOR, and utilizes M-shaped silicon optical waveguides at a wavelength of 1.55 μm. This simulation is conducted through Lumerical FDTD solutions. The suggested waveguide comprises four identical slots, configured in the shape of the letter 'M', and all of which are formed of core silicon and silica cladding. These logic operations work based on constructive and destructive interferences that are caused by phase changes in the input optical beams. The contrast ratio (CR) is employed to quantitatively and comparatively assess the degree to which the target logic operations are efficiently executed. The simulation results indicate that, compared to other reported designs, the considered logic functions constructed using the proposed waveguide can be implemented with higher CRs. The outcomes of this paper can be utilized regarding the implementation of optoelectronic combinational logic circuits of enhanced functionality.

One-step construction of multiplexed enzymatic biosensors using light-addressable electrochemistry on a single silicon photoelectrode

The multiplexed detection of metabolites in parallel within a single biosensor plate is sufficiently valuable but also challenging. Herein, we combine the inherent light addressability of silicon with the high selectivity of enzymes, for the construction of multiplexed photoelectrochemical enzymatic biosensors. To conduct a stable electrochemistry and reagentless biosensing on silicon, a new strategy involving the immobilization of both redox mediators and enzymes using an amide bond-based hydrogel membrane was proposed. The membrane characterization results demonstrated a covalent coupling of ferrocene mediator to hydrogel, in which the mediator acted as not only a signal generator but also a renewable sacrifice agent. By adding corresponding enzymes on different spots of hydrogel membrane modified silicon and recording local photocurrents with a moveable light pointer, this biosensor setup was used successfully to detect multiple metabolites, such as lactate, glucose, and sarcosine, with good analytical performances. The limits of detection of glucose, sarcosine and lactate were found to be 179 μM, 16 μM, and 780 μM with the linear ranges of 0.5–2.5 mM, 0.3–1.5 mM, and 1.0–3.0 mM, respectively. We believe this proof-of-concept study provides a simple and rapid one-step immobilization approach for the fabrication of reagentless enzymatic assays with silicon-based light-addressable electrochemistry.

THERMOREGULATION SYSTEM FOR BIOSENSORS BASED ON FIELD-EFFECT TRANSISTORS WITH A NANOWIRE CHANNEL

In this work we present an automatic thermoregulation system for biosensors based on field-effect transistors with a nanowire channel, which provides full control on the required temperature regime in bioanalytical analises. The system elements, including field-effect transistors with a nanowire channel, temperature sensors and heaters, were fabricated on a single silicon cristal using electron beam lithography, reactive ion etching and high-vacuum deposition techniques. Unicue electronics have been developed to control and maintain temperature. The dependence of thermometer readout on heating power was measured, which is in good agreement with the results of numerical simulation. A demonstration of a thermoregulation system with PID-feedback was carried out, ensuring the establishment of a desiered temperature in the range of 30-70◦ C in 18 s in liquid. A demonstration of a thermoregulation system for detecting nucleic acids was carried out using synthetic single-stranded DNA, which is a gene fragment from the bacterium Escherichia coli. The minimal detectable response was observed for a sample with a concentration of 3 fM.

Qudit-Based Spectroscopy for Measurement and Control of Nuclear-Spin Qubits in Silicon Carbide.

Nuclear spins with hyperfine coupling to single electron spins are highly valuable quantum bits. Here we probe and characterize the particularly rich nuclear-spin environment around single silicon vacancy color centers (V2) in 4H-SiC. By using the electron spin-3/2 qudit as a four level sensor, we identify several sets of ^{29}Si and ^{13}C nuclear spins through their hyperfine interaction. We extract the major components of their hyperfine coupling via optical detected nuclear magnetic resonance, and assign them to shells in the crystal via the density function theory simulations. We utilize the ground-state level anticrossing of the electron spin for dynamic nuclear polarization and achieve a nuclear-spin polarization of up to 98±6%. We show that this scheme can be used to detect the nuclear magnetic resonance signal of individual spins and demonstrate their coherent control. Our work provides a detailed set of parameters and first steps for future use of SiC as a multiqubit memory and quantum computing platform.

Growth optimization and crossover of transport mechanisms in Bi2Se3 thin films

We report the growth, structural characterization, and transport studies of Bi2Se3 thin film on single crystalline silicon (Si), Si/SiO2, quartz, and glass substrates by thermal evaporation method. Our results show that 300 °C is the optimum substrate temperature to obtain the c-axis (001) oriented Bi2Se3 films on all the substrates. The film grown on the Si substrate has the minimum crystalline disorder. The energy-dispersive x-ray spectroscopy results show that film on Si substrate is bismuth deficient, the film on Si/SiO2 substrate is selenium deficient, and the film on quartz substrate is near perfect stoichiometric providing a way to tune the electronic properties of Bi2Se3 films through substrate selection. The film grown on quartz shows the highest mobility (2.7 × 104 cm2 V-1s−1) which drops to 150 cm2 V-1s−1 for Si, 60 cm2 V-1s−1 for Si/SiO2, and 0.9 cm2 V-1s−1 for glass substrate. Carrier concentration is n-type for Bi2Se3 films on Si (∼1018 cm−3), quartz (∼1018 cm−3) and Si/SiO2 (∼1019 cm−3) substrate with a clear indication of frozen out effect around 50 K for Si/SiO2 and Si substrate. Longitudinal resistivity of Bi2Se3 film on Si/SiO2 substrate shows different behavior in three different temperature regions: temperature dependent resistivity region due to electron–phonon scattering, a nearly temperature independent resistivity region due to electron–phonon and electron–ion scattering, and a quantum coherent transport region.

Power-to-Noise Optimization in the Design of Neural Recording Amplifier Based on Current Scaling, Source Degeneration Resistor, and Current Reuse.

This article presents the design of a low-power, low-noise neural signal amplifier for neural recording. The structure reduces the current consumption of the amplifier through current scaling technology and lowers the input-referred noise of the amplifier by combining a source degeneration resistor and current reuse technologies. The amplifier was fabricated using a 0.18 μm CMOS MS RF G process. The results show the front-end amplifier exhibits a measured mid-band gain of 40 dB/46 dB and a bandwidth ranging from 0.54 Hz to 6.1 kHz; the amplifier's input-referred noise was measured to be 3.1 μVrms, consuming a current of 3.8 μA at a supply voltage of 1.8 V, with a Noise Efficiency Factor (NEF) of 2.97. The single amplifier's active silicon area is 0.082 mm2.

Analysis of Lanthanum Oxide Based Double-Gate SOI MOSFET using Monte-Carlo Process.

This work proposes a Double-Gate (DG) MOSFET with a Single Material made of Silicon On-Insulator (SOI). The Lanthanum Oxide material with a high k-dielectric constant has been used as an interface between two gates and the channel. The Monte Carlo analysis has been used to determine the Conduction Band Energy (Ec) profiles and electron sheet carrier densities (ns) for a Silicon channel thickness (tsi) of 10 nm at 0.5 V gate drain-source voltages. The transverse electric fields are weak at the midchannel of DG SOI MOSFETs, where quantum effects are encountered. The Monte Carlo simulation has been confirmed to be effective for high-energy transport. A particle description reproduces the granularity property of the transport for nanoscale modeling. This work utilizes a Monte Carlo (MC) Simulation for the proposed Double Gate Single Material Silicon On Insulator MOSFET with (La2O3=2 nm) as dielectric oxide on upper and lower gate material. The electrical properties of the DG SOI MOSFETs with Lanthanum Oxide were analyzed using Monte Carlo simulation, including the conduction band energy, electric field, potential distribution, particle movement, and average velocity. The peak electric field (E) simulation results and an average drift velocity (υavg) of 6Í105 V/cm and 1.6Í107 cm/s were obtained, respectively. The conduction band energy for the operating region of the source has been observed to be 4 % to the drain side, which obtained a value of -0.04 eV at the terminal end. This proposed patent design, such as double-gate SOI-based devices, is the best suggestion for significant scalability challenges. Emerging technologies reach the typical DG SOI MOSFET's threshold performance when their geometrical dimensions are in the nanometer region. This device based on nanomaterial compounds has been more submissive than conventional devices. The nanomaterials usage in the design is more suitable for downscaling and reducing packaging density.

Polytypic transformation behavior from 4H-SiC to 3C-SiC during high-speed scratching of single crystalline silicon carbide

The phase transformation behavior and associated mechanism of 4H-SiC induced by dynamic processing at room temperature conditions can be investigated with high-speed scratching tests. A dedicated high-speed scratching setup is developed to achieve the speed range over 10 m/s to 30 m/s while microscopic detection is performed to study the microstructural alteration of 4H–SiC. Raman spectra analyses indicate that the polytypic transformation from 4H to 3C occurs during high-speed scratching of single crystalline silicon carbide. Transmission electron microscopy demonstrates a shift in the stacking order of the atomic layers to face-centered cubic at the subsurface of the scratched groove, which reveals the formation mechanism of 3C-SiC. Furthermore, the 4H to 3C polytypic transformation exhibits a sensitive scratching speed correlation. The research can enhance the fundamental understanding of the mechanisms of damage formation during manufacturing of 4H-SiC components and provide g guidance for high-quality processing of 4H-SiC crystals.

Quantum simulator on a single chip

Effective quantum simulators could enable researchers to gain deeper insights into unresolved questions in physics. Researchers in the EPIQUS project are working to develop a quantum simulator on a single silicon chip, bringing together electronic, photonic and quantum components, as Dr Mher Ghulinyan explains.

300-Gbit/s/λ 8-Level Pulse-Amplitude-Modulation (PAM8) with a silicon microring modulator utilizing long short term memory regression and deep neural network classification

We present the first experimental demonstration up the authors' knowledge a high-capacity short-reach optical communication link which employs a long-short-term-memory (LSTM) and deep-neural-network (DNN) for enabling 300-Gbit/s (100 Gbaud) 8-level pulse amplitude modulation (PAM8) generated by a single 55-GHz bandwidth silicon microring modulator (SiMRM) with a driving voltage of 1.8-Vpp. As PAM8 modulation has a lower average level-to-level transition energy when compared with that in PAM4, it could be possible to achieve higher energy efficiency when utilizing PAM8 at the same driving voltage. To recover the PAM8 modulation, LSTM and DNN are utilized for regression and classification respectively. The LSTM contains memory cells for dealing with signal time domain dependencies, and has the ability to store, read, and reject data passing through the neural network. The subsequent DNN performs the classification of the 8 levels. Experimental results show that 300 Gbit/s PAM8 modulation is achieved at back-to-back (B2B) and 270 Gbit/s PAM8 is achieved after 1 km standard single-mode-fiber (SSMF) transmission satisfying the soft-decision forward error correction (SD-FEC) bit-error-rate requirement (BER) of 2.4 × 10-2.

Perovskite/silicon tandem solar cells-compositions for improved stability and power conversion efficiency.

Perovskite/Silicon Tandem Solar Cells (PSTSCs) represent an emerging opportunity to compete with industry-standard single junction crystalline silicon (c-Si) solar cells. The maximum power conversion efficiency (PCE) of single junction cells is set by the Shockley-Queisser (SQ) limit (33.7%). However, tandem cells can expand this value to ~ 45% by utilising two stacked solar cells to harvest the solar spectrum more efficiently. 33.9% PCE has already been achieved with PSTSCs. This perspective analyses recent advances in PSTSC technology, with an emphasis on optimal perovskite composition, the problem and mitigation of light-induced halide phase segregation, self-assembled hole transporting monolayers and additives that can improve and stabilise the perovskite. Top-performing compositions show three cationic components (Cs+, FA+, Pb2+) and three anionic (I-, Br-, Cl-) with a bandgap between 1.55 and 1.77eV and a theoretical maximum of 1.73eV (717nm). Anionic additives such as (Br3)- and SCN- reduce trap states and segregation. 2D-perovskite grain boundary interfaces are created with cationic alkylammonium additives such as methyl-phenethylammonium (MPEA) and result in improved performance. 2-, 3- or 4-terminal devices with a (partly) textured silicon heterojunction (SHJ) bottom cell are ideal. An ultra-thin interfacial recombination layer (~ 5nm) of indium tin oxide (ITO) or indium zinc oxide (IZO) containing a carbazole-based hole transporting self-assembled monolayer (Me-4PACz) is used for optimal 2-terminal tandem devices.

Robust reconfigurable radiofrequency photonic filters based on a single silicon in-phase/quadrature modulator

Abstract Combining integrated photonics and radiofrequency (RF) signals in the optical domain can help overcome the limitations of traditional RF systems. However, it is challenging to achieve environmentally insensitive filtering in wireless communications using integration schemes. In this report, the performance of robust RF filters based on a single silicon in-phase/quadrature modulator with significantly improved temperature and optical carrier wavelength sensitivities, which were suppressed by more than three orders of magnitude compared with those of silicon resonators, was experimentally evaluated. Upconversion and the processing of signals were simultaneously realized on the modulator by setting the relative phases of the arms and the bias voltages. Moreover, the filters can be reconfigured as low-pass, high-pass, band-pass, or band-stop filters. From 25 to 75 °C, the center frequency variation was within 0.2 GHz. From 1500 to 1600 nm, the center frequency variation was within 2 GHz. The proposed scheme allows for filtering and reconfiguration without the use of optical processing modules such as resonators or delay lines, thus providing a novel approach to signal processing and a new robust filter for scenarios with dynamic environments.

Finite element modeling and analysis method for predicting and optimizing the warpage of construction before flip chip bonding in System-on-Wafer process flow

As one of the solutions to surpass the limitations of Moore's Law in the post-Moore era, System-on-Wafer (SoW) technology provides the capability to integrate multiple chip components onto a single silicon wafer. A new high-density integrated SoW solution is discussed in this article. However, significant warpage can result from mismatches in the coefficients of thermal expansion (CTE) of different materials in a 12-in. wafer, presenting considerable challenges for the flip chip (FC) bonding, installation of power delivery and heat dissipation systems. Severe warpage can directly lead to the failure of the entire system. Therefore, pre-assessment and optimization of the warpage are crucial. This paper proposes a multi-scale modeling approach to assess the wafer warpage prior to FC bonding in the SoW fabrication process. To evaluate the accuracy of the modeling approach, a dummy die to thinned wafer and molding (DDTWM) was first designed and fabricated. The sole distinction in fabrication process between DDTWM and SoW is the absence of through silicon via (TSV) and backend of line (BEOL) metal traces. The simulation and experiment for DDTWM achieve a good level of consistency. In addition, following the completion of warpage simulations on the actual SoW structure prior to FC bonding, utilizing the same modeling approach, we proceeded to perform a Response Surface Methodology (RSM) analysis on several crucial parameters that exert influence on warpage. Subsequent to analyzing the results, optimization simulations were executed, underscoring the significant instructive value of RSM analysis in optimizing warpage within the structure prior to FC bonding in the SoW manufacturing process. This work offers an effective solution for predicting and mitigating substrate warpage prior to FC bonding in the SoW fabrication process, contributing to comprehensive warpage control.

Enhancing the Emission Rate of the Inherent Silicon‐Vacancy Center Using Optimized Multipolar Moments in a Silicon Carbide Metasurface

AbstractSilicon carbide (SiC) hosts various color centers with emission lines from visible to near‐infrared, with promising applications in quantum communication. Metasurfaces made using SiC can enhance the emission rate of inherent color centers to achieve on‐demand single photon emission with a high emission rate. This is possible by engineering the amplitude and phase of the excited multipolar scattering moments in metasurfaces. The numerical simulations and analytical calculations are used to study the emission rate enhancement from an embedded single silicon vacancy () center in SiC metasurface. The optimized metasurface balances multipolar moments at the zero‐phonon line wavelength of 862 nm with 40 times field intensity confinement. The confinement provides substantial emission rate enhancement for the center, making it a bright single photon emitter at 862 nm. The significant emission enhancement offers new insights into the metasurface to achieve on‐demand single‐photon sources and efficient spin–photon interfaces.

A deep learning based latency aware predictive routing model for network‐on‐chip architectures

SummaryNetwork on Chip (NoC) is an evolving platform for communications related applications, which are executed on a single silicon chip. There are several routing models in NoC architectures, but the accuracy of these models is limited, and the existing models are degraded because of over and under fitting issues. This research introduces the new deep learning‐based latency aware predictive routing model for on‐chip networks to route packets with better performance and power efficiency. The deep learning model used in this research is a new convolutional residual gated recurrent unit (CRGRU) with queuing theory. Moreover, the source and channel queuing delay is comprised of features to learn spatial and sequential information that improves the overall prediction accuracy. This router is modified by the intrusion of the Router States Monitor unit and the CRGRU hardware engine. The work is executed using the Xilinx platform, and the performance measures like latency and throughput are obtained by varying the network size as , , and and also varying the buffer space and length as , , and , respectively. In addition, the squared correlation coefficient (SCC) and normalized root mean square error (NRMSE) are evaluated and compared with existing learning models to validate the proposed model.