Array Device Research Articles

Highly Coercive L10-Phase Dots Obtained through Low Temperature Annealing for Nano-Logic Magnetic Structures

Nano-logic magnetic structures are of great interest for spintronic applications. While the methods used for developing arrays of magnetic L10-phase dots are, in most cases, based on deposition followed by annealing at high temperatures, usually around 700 °C, we demonstrate here a technique where a much lower annealing temperature (i.e., 400 °C) is needed in order to promote fully the disorder–order phase transformation and achievement of highly coercive L10-phase dots. In order to develop building blocks based on arrays of L10-phase FePt dots for further spintronic applications, an engraving technique using electron beam lithography is employed. This paper describes the fabrication, as well as the morphological and magnetic characterization, of regularly placed FePt dots of various shapes, as pre-requisites for integration into nano-logic devices. As a proof of concept, regular arrays of FePt circular dots were devised and their structural characterization, using X-ray diffraction (XRD) and transmission electron microscopy (TEM), was performed. It has been shown that annealing at only 400 °C for 30 min proved the occurrence of the tetragonal L10 phase. Moreover, structural characterization showed that the disorder–order phase transformation was complete with only the L10 phase detected in high resolution TEM. The magnetic characterization provided more insight into the potential of such arrays of magnetic devices with convenient values of magnetic coercivity, remanent and saturation magnetization. These findings show good potential for developing regular arrays of uniformly shaped magnetic entities with encouraging magnetic performances in view of various applications.

Fabrication of a self-aligned multi-waveguide-layer passive Si3N4/SiO2 photonic integrated circuit for a 3-D optical phased array device

Most traditional PICs (photonics integrated circuits) are based on a single-waveguide-layer configuration, which takes advantage of the mature fabrication process from the EIC (electronic integrated circuits) industry; but in the meantime, this configuration also limits the performance of PICs in applications such as OPA (optical phased array) devices. We have proposed a multi-waveguide-layer 3-D (3 dimensional) OPA device and demonstrated its unique advantage in broadband high efficiency. In this paper, we present the fabrication process of the proposed 3-D OPA in detail. By developing the fabrication process with a single lithography step, we address the two potential issues in a multi-waveguide-layer PIC: the alignment between layers; and the accurate spacing control between layers. The detailed considerations of processes are also elaborated, especially in the PR (photoresist) exposure and etching.

Simultaneous Sensing of Velocity and Position of a Moving Light Source Using Metal-Insulator-Semiconductor Structures.

Photodetectors based on semiconductor devices have been widely used to sense light position, intensity, and wavelength. However, monitoring the motion velocity of a light beam generally requires complex integration of device arrays. Here, we report a single device of a simple metal-insulator-semiconductor structure for self-powered sensing not only position but also velocity of a light beam or shadow. A velocity-dependent voltage output between two terminals of the metal is observed. It is attributed to light illumination-induced local surface potential change in semiconductors and the following movement of local charges accumulated in the metal due to capacitive coupling. The amplitude of the velocity-dependent voltage can be facilely modulated by applying a gate voltage. These results shed light on compact devices with multiple sensing functions.

In situ construction of PtSe2/Ge Schottky junction array with interface passivation for broadband infrared photodetection and imaging

AbstractInfrared (IR) detection is vital for various military and civilian applications. Recent research has highlighted the potential of two‐dimensional (2D) topological semimetals in IR detection due to their distinctive advantages, including van der Waals (vdW) stacking, gapless electronic structure, and Van Hove singularities in the electronic density of states. However, challenges such as large‐scale patterning, poor photoresponsivity, and high dark current of photodetectors based on 2D topological semimetals significantly impede their wider applications in low‐energy photon sensing. Here, we demonstrate the in situ fabrication of PtSe2/Ge Schottky junction by directly depositing 2D PtSe2 films with a vertical layer structure on a Ge substrate with an ultrathin AlOx layer. Due to high quality junction, the photodetector features a broadband response of up to 4.6 μm, along with a high specific detectivity of ~1012 Jones, and operates with remarkable stability in ambient conditions as well. Moreover, the highly integrated device arrays based on PtSe2/AlOx/Ge Schottky junction showcases excellent Mid‐IR (MIR) imaging capability at room temperature. These findings highlight the promising prospects of 2D topological semimetals for uncooled IR photodetection and imaging applications.image

Light-emitting MOS junction for ultrahigh-resolution quantum dot displays

A high-resolution quantum-dot (QD) light-emitting device array is considered to be the key component in a high resolution near-eye micro-display. Although much research has been committed to the achievement of a high-resolution QD pattern, realizing a sub-10 micrometer or even a sub-micrometer device array is challenging because of the requirement for precise vertical multilayer alignment and the existence of electric-crosstalk effects. In this work, we propose a QD-based light-emitting metal/oxide/semiconductor junction (LE-MOSJ) with a super-simple structure of ITO/Al2O3/QDs/Ag with no injection or transfer layer. We measured the voltage-frequency-electroluminescence, spectrum-voltage, and spectrum-frequency characteristics, used voltage-dependent time-resolved electroluminescence to analyze the carrier transport behavior and the working mechanism, and attribute the electron source for the electroluminescence to free and surface defect-captured electrons. Finally, we successfully demonstrate an ultrahigh-resolution LE-MOSJ array with ∼4200 pixels per inch (PPI). We believe the proposed LE-MOSJ can provide an optional approach for realizing ultrahigh-resolution QD-based display technology.

Laser fabrication of lead selenide infrared focal plane array devices

The motivation of this work is to demonstrate the versatility and potential of laser processing in the fabrication of PbSe thin films and focal plane array devices. This work fabricates an FPA device with any need for the suite of equipment and chemicals necessary for photolithography and etching. Advances in laser technologies and the vast number of laser parameters available are enabling the huge potential for laser processing of thin films and device fabrication. This can be accomplished faster using lasers with fewer steps than using conventional thin film deposition and photolithography methods. This work presents the fabrication and simple operation of a proof-of-concept PbSe-based, 120-pixel PFA (10 × 12 pixel) focal plane array using only laser processing for film deposition and device patterning. Lasers were used to both deposition and pattern a PbSe film with 60 × 70 µm pixels with 100 µm pitch with a unit cell photoresponse of 17% DelR. Additional results, challenges, limitations, and suggested future improvements are presented.

Design and fabrication of cryogenic multiplexing control chip

This paper presents a design and fabrication process of a cryogenic multiplexing control chip (MCC) for superconducting quantum computers. The working temperature of MCC can be 10 ∼ 30 mK, because it could be integrated with quantum processor in the same package. With a multiplexing ratio of 1:4 and designed working frequency 4–8 GHz, the MCC is a non-reciprocity device which consisted of bandpass filters and isolators, which are based on tunable inductor bridges (TIB). The MCC chip size is 6 × 6 mm2 and includes λ/2 coplanar waveguides resonators, superconducting quantum interference device arrays, capacitors, low pass filters, baluns and bias lines. Adopting self-aligned process of Josephson junctions, the fabrication of MCC constitutes four lithography masks. The modular design of MCC could facilitate the development of large-scale superconducting quantum computers.

Towards Maximising Hardware Resources and Design Efficiency via High-Speed Implementation of HMAC based on SHA-256 Design

Some applications, such as Message Authentication Code (MAC), rely on different hashing operations. There are various hash functions, including Message-Digest 5 (MD5), RACE Integrity Primitives Evaluation Message Digest 160 (RIPEMD-160), Secure Hash Algorithm 1 (SHA-1), and Secure Hash Algorithm 256 (SHA-256), among others. The network layer is the third of seven layers of the Open Systems Interconnection (OSI) concept, also known as the Internet. It handles network addressing and physical data routing. Nowadays, enhanced internet security is necessary to safeguard networks from illegal surveillance. As a result, Internet Protocol Security (IPsec) introduces secure communication across the Internet by encrypting and/or authenticating network traffic at the IP level. IPsec is an internet-based security protocol. Encapsulating Security Payload (ESP) and Authentication Header (AH) protocols are separated into two protocols. The MAC value is stored in the authentication data files of the Authentication Header and Encapsulating Security Payload. This article analyses a fast implementation of the Hash-based Message Authentication Code (HMAC), which uses its algorithm to ensure the validity and integrity of data to optimise hardware efficiency and design efficacy using the SHA-256 algorithm. During data transfer, HMAC is critical for message authentication. It was successfully developed using Verilog Hardware Description Language (HDL) code with the implementation of a Field Programmable Gate Array (FPGA) device using the Altera Quartus II Computer-Aided Design (CAD) tool to enhance the maximum frequency of the design. The accuracy of the HMAC design, which is based on the SHA-256 design, was examined and confirmed using ModelSim. The results indicate that the maximum frequency of the HMAC-SHA-256 design is approximately 195.16 MHz.

Artificial Visual Synaptic Architecture with High-Linearity Light-Modulated Weight for Optoelectronic Neuromorphic Computing.

A brain-like neuromorphic computing system, as compared with traditional Von Neumann architecture, has broad application prospects in the fields of emerging artificial intelligence (AI) due to its high fault tolerance, excellent plasticity, and parallel computing capability. A neuromorphic visuosensory and memory system, an important branch of neuromorphic computing, is the basis for AI to perceive, process, and memorize optical information, now still suffering from nonlinearity of synaptic weight, crosstalk issues, and integration incompatibility, hindering the high-level training and inference accuracy. In this work, we propose a new optoelectronic neuromorphic architecture by integrating an electrochromic device and a perovskite photodetector. Ascribing to the superior memory characteristics of the electrochromic device and sensitive light response of the perovskite photodetector, the neuromorphic device shows typical visual synaptic functionalities such as light triggering, neural facilitation, long-term potentiation, and depression (LTP and LTD). Furthermore, by adjusting the intensity and wavelength of external light signals, the visual synaptic function of the device can be modulated, enabling the device to exhibit high weight linearity in all current output ranges and improve information processing capability and image recognition accuracy. Moreover, both the electrochromic and perovskite layers possess the advantage of large area fabrication and integration, which enables the fabrication of large device arrays with high integration compatibility and scalability. In this study, 10 × 10 device arrays are demonstrated and each device shows uniform light responses, memory behaviors, and synaptic performances. MNIST and CIFAR-10 algorithms are used to simulate the image recognition properties of the synaptic architecture, and the calculated recognition accuracy is 97.94 and 91.04%, respectively, with an error less than 2.5%. The proposed artificial visual neuromorphic architecture will provide a potential device prototype for efficient visual neuromorphic systems.

Dual-mode Conversion of Photodetector And Neuromorphic Vision Sensor via Bias Voltage Regulation on A Single Device.

For optoelectronic devices that convert optical signal to electrical signal, they can have a fast photoresponse speed to function as a photodetector, or possess the ability to perceive, memorize and process images to act as a neuromorphic vision sensor (NVS). However, the simultaneous implementation of photodetector and NVS on a single device faces a great challenge, due to the contradiction of photoresponse speed. In this work, to simultaneous achieve this complex function in a single device, trench-bridged GaN/Ga2 O3 /GaN back-to-back double heterojunction array device is fabricated. Interestingly, the device shows fast photoresponse and persistent photoconductivity behavior at low and high voltages, respectively, through the modulation of oxygen vacancy ionization and de-ionization processes in Ga2 O3 . Consequently, the role of the optoelectronic device can be altered between photodetector and NVS by simply adjusting the bias voltage. As a photodetector, the device is able to realize fast optical imaging and optical communication functions. On the other hand, the device exhibits outstanding image sensing, image memory, and neuromorphic visual pre-processing as a NVS. The utilization of NVS for image pre-processing leads to a noticeable enhancement in both the recognition accuracy and efficiency. The results presented in this work not only offer a new avenue to obtain complex functionality on a single optoelectronic device, but also provide the opportunities to implement advanced robotic vision systems and neuromorphic computing. This article is protected by copyright. All rights reserved.

Installation and capacity performance of multi-line dynamically installed anchors

The multi-line anchor achieves the ‘anchor sharing’ goal by allowing multiple floating devices to be moored, such that the total number of anchors in a floating device array can be reduced significantly. This study proposes a dynamically installed anchor with the potential of resisting uplift loads from varied directions. The multi-line anchor is dynamically installed with the aid of a booster. The installation performance of the hybrid anchor (i.e. multi-line anchor + booster) is first examined by field tests. Then finite-element analyses are performed to investigate the uplift capacity of the anchor under V-H-M-T combined loading conditions. Based on the numerical results, yield envelopes are established for assessing the ultimate bearing capacity of the anchor. Additionally, model tests are conducted to quantitatively study the installation and set-up effects on the uplift capacity of the anchor, indicating the vertical and torque capacities are sensitive to the installation effect. Finally, a design framework is proposed to assess the stability of the multi-line anchor under combined loading conditions.

Construction of a Compact Array of Microplasma Jet Devices and Its Application for Random Mutagenesis of Rhodosporidium toruloides.

A small and efficient DNA mutation-inducing machine was constructed with an array of microplasma jet devices (7 × 1) that can be operated at atmospheric pressure for microbial mutagenesis. Using this machine, we report disruption of a plasmid DNA and generation of mutants of an oleaginous yeast Rhodosporidium toruloides. Specifically, a compact-sized microplasma channel (25 × 20 × 2 mm3) capable of generating an electron density of greater than 1013 cm-3 was constructed to produce reactive species (N2*, N2+, O, OH, and Hα) under helium atmospheric conditions to induce DNA mutagenesis. The length of microplasma channels in the device played a critical role in augmenting both the volume of plasma and the concentration of reactive species. First, we confirmed that microplasma treatment can linearize a plasmid by creating nicks in vitro. Second, we treated R. toruloides cells with a jet device containing 7 microchannels for 5 min; 94.8% of the treated cells were killed, and 0.44% of surviving cells showed different colony colors as compared to their parental colony. Microplasma-based DNA mutation is energy-efficient and can be a safe alternative for inducing mutations compared to conventional methods using toxic mutagens. This compact and scalable device is amenable for industrial strain improvement involving large-scale mutagenesis.

CULTIVATING SPIRITUALITY WHEN AND WHERE IT IS NEEDED MOST: CHILDREN, PARENTS, HOMES, AND FAMILIES

Given all the life-threatening problems in the world and prospects for the future, there could be no better time to focus attention on cultivating spirituality when and where it is needed most, namely in the lives of children, parents, homes, and families. We cannot expect to experience more peace, harmony, happiness, and stability in the world and our lives – as well as less violence, conflict, animosity, war, and aggression – without according a much higher priority to how children are brought into the world, grow up, the many experiences they have in their homes with their parents and families, their encounters with spirituality when they are young, and the education and training they need to prepare them properly for living in the world of the present and the future. Helping children to develop “strong roots” and “healthy wings” is the key to this. The strong roots are required to enable children to deal with all the necessities, practicalities, realities, problems, and challenges they will encounter at this crucial stage in their lives as well as throughout life; and the healthy wings are needed to enable them to fly high and far as well as to realize their full potential. A great deal of attention should be paid by parents and families to children’s experiences in the arts, humanities, ethics, the sciences, the natural environment, and heritage of history at this time, as well as learning systems, methods, and techniques developed by such scholars as Shinichi Suzuki, Rudolph Steiner, Maria Montessori. John Dewey, Jean Piaget, Paulo Freire, and Confucius, as well as to character education. This is also a perfect time to expose children to the spiritual and exemplary lives of Albert Schweitzer, Mahatma Gandhi, Martin Luther King, Jr., Mother Teresa, and many other people, as well as to broaden and deepen their expose to the holistic character of culture and the many diverse cultures in the world through the rich array of technological, digital, visual, verbal, and virtual devices that now exist and are available in the world. While spirituality requires going deep into “the self,” its ideal travelling companion - compassion - requires making strong connections with “the other” and the world at large. Working in combination, these two powerful forces and capabilities possess the potential to change the world and change it for the better for all people and all countries, the world as a whole, and the human family in the years and decades ahead.

Pave the way to the batch production of SWNT arrays for carbon-based electronic devices

Pave the way to the batch production of SWNT arrays for carbon-based electronic devices

Improved Nonlinear Statistical Photocalibration of Photodetectors Without Calibrated Light Sources

The calibration of charge coupled device arrays is commonly conducted using dark frames. Nonabsolute calibration techniques only measure the relative response of the detectors. A recent attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection statistics that relied on a nonlinear model was shown to be successful but was highly susceptible to the readout noise present in the measurement. This effort produced the nonlinear statistical nonuniformity calibration (NLSNUC) algorithm, which demonstrated an ability to better model the output of photodetector array elements than similar techniques that relied on a linear model. In this paper, a modified three-point NLSNUC photocalibration procedure is defined that requires only first and second moments of the measurements and allows the response to be modeled using a nonlinear function over the dynamic range of the detector. The modified NLSNUC technique is applied to image data containing a light source with a known output power. Estimates of the number of photoelectrons measured by the detector are shown to be superior to those obtained by the original NLSNUC algorithm as well as other statistical calibration techniques that do not utilize a calibrated light source.

Optimization of graphene-based quantum Hall arrays for recursive star–mesh transformations

A mathematical approach is adopted for optimizing the number of total device elements required for obtaining high effective quantized resistances in graphene-based quantum Hall array devices. This work explores an analytical extension to the use of star–mesh transformations such that fractal-like, or recursive, device designs can yield high enough resistances (like 1 EΩ, arguably the highest resistance with meaningful applicability) while still being feasible to build with modern fabrication techniques. Epitaxial graphene elements are tested, whose quantized Hall resistance at the ν=2 plateau (RH≈ 12 906.4 Ω) becomes the building block for larger effective, quantized resistances. It is demonstrated that, mathematically, one would not need more than 200 elements to achieve the highest pertinent resistances.

A Parallax Shift Effect Correction Based on Cloud Top Height for FY-4A Lightning Mapping Imager (LMI)

The Lightning Mapping Imager (LMI) onboard the Fengyun-4A (FY-4A) satellite is the first independently developed satellite-borne lightning imager in China. It enables continuous lightning detection in China and surrounding areas, regardless of weather conditions. The FY-4A LMI uses a Charge-Coupled Device (CCD) array for lightning detection, and the accuracy of lightning positioning is influenced by cloud top height (CTH). In this study, we proposed an ellipsoid CTH parallax correction (ECPC) model for lightning positioning applicable to FY-4A LMI. The model utilizes CTH data from the Advanced Geosynchronous Radiation Imager (AGRI) on FY-4A to correct the lightning positioning data. According to the model, when the CTH is 12 km, the maximum deviation in lightning positioning caused by CTH in Beijing is approximately 0.1177° in the east–west direction and 0.0530° in the north–south direction, corresponding to a horizontal deviation of 13.1558 km, which exceeds the size of a single ground detection unit of the geostationary satellite lightning imager. Therefore, it is necessary to be corrected. A comparison with data from the Beijing Broadband Lightning Network (BLNET) and radar data shows that the corrected LMI data exhibit spatial distribution that is closer to the simultaneous BLNET lightning positioning data. The coordinate differences between the two datasets are significantly reduced, indicating higher consistency with radar data. The correction algorithm decreases the LMI lightning location deviation caused by CTH, thereby improving the accuracy and reliability of satellite lightning positioning data. The proposed ECPC model can be used for the real-time correction of lightning data when CTH is obtained at the same time, and it can be also used for the post-correction of space-based lightning detection with other cloud top height data.

Accurate Weight Update in an Electrochemical Random‐Access Memory Based Cross‐Point Array Using Channel‐High Half‐Bias Scheme for Deep Learning Accelerator

AbstractRecently cross‐point arrays of synaptic memory devices have been intensively studied to accelerate deep neural network computations. Among various synaptic devices, electrochemical random‐access memory (ECRAM) is emerging as a promising non‐volatile memory candidate owing to its superior synaptic characteristics. However, an optimized update scheme for a three‐terminal ECRAM‐based cross‐point array is yet to be developed. In this study, a metal‐oxide‐based ECRAM (MO‐ECRAM) shows superior synaptic characteristics and the weight update of devices in the MO‐ECRAM cross‐point array is analyzed using the half‐bias (HB) scheme. Additionally, A channel‐high half‐bias (CHB) scheme is proposed to overcome the degraded selectivity of the weight update caused by the three‐terminal configuration of the ECRAM device. In the CHB scheme, the conductance change in the selected device can be increased considerably by applying a calculated additional voltage to the channel. Using the CHB scheme, parallel and selective updates are successfully performed in a 2 × 2 MO‐ECRAM cross‐point array. Finally, an experimental demonstration of the training algorithm shows the impact of selective updates when using the CHB scheme. This new update scheme is expected to improve training accuracy in ECRAM cross‐point array‐based deep learning accelerators.

Open-loop analog programmable electrochemical memory array

Emerging memories have been developed as new physical infrastructures for hosting neural networks owing to their low-power analog computing characteristics. However, accurately and efficiently programming devices in an analog-valued array is still largely limited by the intrinsic physical non-idealities of the devices, thus hampering their applications in in-situ training of neural networks. Here, we demonstrate a passive electrochemical memory (ECRAM) array with many important characteristics necessary for accurate analog programming. Different image patterns can be open-loop and serially programmed into our ECRAM array, achieving high programming accuracies without any feedback adjustments. The excellent open-loop analog programmability has led us to in-situ train a bilayer neural network and reached software-like classification accuracy of 99.4% to detect poisonous mushrooms. The training capability is further studied in simulation for large-scale neural networks such as VGG-8. Our results present a new solution for implementing learning functions in an artificial intelligence hardware using emerging memories.

Near‐Infrared Optical Synapses Based on Multilayer MoSe2 Moiré Superlattice for Artificial Retina

AbstractNear‐infrared (NIR) synaptic devices have attracted great attention in the field of NIR vision sensors due to their highly parallel sensing and memory functions, which emulate the basic biomimetic behaviors of the human visual system. However, it is a great challenge for the 2D material to achieve NIR light response and integration, which obstructs the progress of NIR synaptic devices. Hence, a two‐terminal NIR synaptic device based on a multilayer MoSe2 moiré superlattice is reported. The moiré structure dominated by interlayer excitons significantly enhances the interlayer coupling of multilayer MoSe2, resulting in a narrower band gap nearly to that of bulk to achieve NIR light response and broadband absorption from 240 nm to 1700 nm. The existence of Se vacancies in MoSe2 moiré superlattice makes the device show the fundamental synaptic performance. Furthermore, a 10×10 integrated retinal morphologic device array is constructed. Under the 100 s light pulse stimulation of 1060 nm, the pattern obtained after attenuation of 50 s still has a memory level of 14.84%, reflecting the excellent storage function under NIR illumination. This research opens up a new avenue for the realization of NIR artificial retina and bionic eye based on 2D materials.