The effect ofγ-ray irradiation on the SOT magnetic films and Hall devices

Magnetoresistive random access memories(MRAMs)have drawn the attention of radiation researchers due to their potential high radiation tolerance.In particular,spin-orbit torque MRAM(SOT-MRAM)has the best performance on endurance and access speed,which is considered to be one of the candidates to replace SRAM for space application.However,little attention has been given to theγ-ray irradiation effect on the SOT-MRAM device yet.Here,we report the Co-60 irradiation results for both SOT(spin-orbit torque)magnetic films and SOT-Hall devices with the same stacks.The properties of magnetic films are not affected by radiation even with an accumulated dose up to 300 krad(Si)while the magnetoelectronic properties of SOTHall devices exhibit a reversible change behavior during the radiation.We propose a non-equilibrium anomalous Hall effect model to understand the phenomenon.Achieved results and proposed analysis in this work can be used for the material and structure design of memory cell in radiation-hardened SOT-MRAM.

A review of automatic detection of epilepsy based on EEG signals

Epilepsy is a common neurological disorder that occurs at all ages.Epilepsy not only brings physical pain to patients,but also brings a huge burden to the lives of patients and their families.At present,epilepsy detection is still achieved through the observation of electroencephalography(EEG)by medical staff.However,this process takes a long time and consumes energy,which will create a huge workload to medical staff.Therefore,it is particularly important to realize the automatic detection of epilepsy.This paper introduces,in detail,the overall framework of EEG-based automatic epilepsy identification and the typical methods involved in each step.Aiming at the core modules,that is,signal acquisition analog front end(AFE),feature extraction and classifier selection,method summary and theoretical explanation are carried out.Finally,the future research directions in the field of automatic detection of epilepsy are prospected.

Analysis of Current Research Status of Plasma Etch Process Model

This paper summarizes the status of the plasma etch process modeling research.It mainly introduces typical etching models employing the analytical method,geometric method,system identification method,basic principle simulation method,as well as empirical model.Each model’s basic principles,application scopes,advantages and disadvantages are discussed.Based on these,the development history of the etch process modeling is summarized,and the development opportunities of the etch model are prospected.This paper provides a brief view for establishment of the plasma etching process model.

Uniform, fast, and reliable CMOS compatible resistive switching memory

Resistive switching random access memory(RRAM) is considered as one of the potential candidates for next-generation memory. However, obtaining an RRAM device with comprehensively excellent performance, such as high retention and endurance, low variations, as well as CMOS compatibility, etc., is still an open question. In this work, we introduce an insert TaO_(x) layer into HfO_(x)-based RRAM to optimize the device performance. Attributing to robust filament formed in the TaO_(x) layer by a forming operation, the local-field and thermal enhanced effect and interface modulation has been implemented simultaneously. Consequently, the RRAM device features large windows(> 10^(3)), fast switching speed(-10 ns), steady retention(> 72h), high endurance(> 10^(8) cycles), and excellent uniformity of both cycle-to-cycle and device-to-device. These results indicate that inserting the TaO_(x) layer can significantly improve HfO_(x)-based device performance, providing a constructive approach for the practical application of RRAM.

Low-thermal-budget Au-free ohmic contact to an ultrathin barrier AlGaN/GaN heterostructure utilizing a micro-patterned ohmic recess

A pre-ohmic micro-patterned recess process,is utilized to fabricate Ti/Al/Ti/TiN ohmic contact to an ultrathin-barrier(UTB)AlGaN/GaN heterostructure,featuring a significantly reduced ohmic contact resistivity of 0.56Ω·mm at an alloy temperature of 550℃.The sheet resistances increase with the temperature following a power law with the index of +2.58,while the specific contact resistivity decreases with the temperature.The contact mechanism can be well described by thermionic field emission(TFE).The extracted Schottky barrier height and electron concentration are 0.31 eV and 5.52×10^(18) cm^(−3),which suggests an intimate contact between ohmic metal and the UTB-AlGaN as well as GaN buffer.A good correlation between ohmic transfer length and the micro-pattern size is revealed,though in-depth investigation is needed.A preliminary CMOS-process-compatible metal-insulator-semiconductor high-mobility transistor(MIS-HEMT)was fabricated with the proposed Au-free ohmic contact technique.

A Novel High Volume Manufacturing Method for Defect-free and High-yield SiN Micro-sieve Membranes

Micro-sieves have been widely used in medical treatment,quarantine,environment,agriculture,pharmacy and food processing.However,the manufacturing and yield improvement have been difficult due to multiple challenges,such as the sieve unit release defect,cracking,and KOH corrosion.In this paper,we report process details and discuss technical difficulties which are usually the root-causes for process failures,and demonstrate a reliable and high yield production of SiNx micro-sieves processed with our novel method,which is also compatible with high volume manufacturing.

CMOS-compatible wafer-scale Si subulate array for superb switching uniformity of RRAM with localized nanofilaments

Resistive switching random access memory(RRAM)is one of the most promising candidates with highdensity three-dimensional integration characteristics for nextgeneration nonvolatile memory technology.However,the poor uniformity issue caused by the stochastic property of the conductive filament(CF)impedes the large-scale manufacture of RRAM chips.Subulate array has been introduced into the RRAM to minimize the CF randomness,but the methods are cumbersome,expensive,or resolution-limited for large-scale preparation.In this work,Si subulate array(SSA)substrates with different curvature radii prepared by a wafer-scale and nanoscale-controllable method are introduced for RRAM fabrication.The SSA structure,which induces a quasi-single CF or a few CFs formed in the tip region(TR)of the device as evidenced by the high-resolution transmission electron microscopy and energy dispersive spectroscopy characterization,dramatically improves the cycle-to-cycle and device-to-device uniformity.Decreasing the curvature radius of the TR significantly improves the device performance,including switching voltages,high/low resistance states,and retention characteristics.The improved uniformity can be attributed to the enhanced local electric field in the TR.The proposed SSA provides a low-cost,uniform,CMOS-compatible,and nanoscale-controllable optimization strategy for the largescale integration of highly uniform RRAM devices.

Applications of MXenes in human-like sensors and actuators

Human beings perceive the world through the senses of sight,hearing,smell,taste,touch,space,and balance.The first five senses are prerequisites for people to live.The sensing organs upload information to the nervous systems,including the brain,for interpreting the surrounding environment.Then,the brain sends commands to muscles reflexively to react to stimuli,including light,gas,chemicals,sound,and pressure.MXene,as an emerging two-dimensional material,has been intensively adopted in the applications of various sensors and actuators.In this review,we update the sensors to mimic five primary senses and actuators for stimulating muscles,which employ MXene-based film,membrane,and composite with other functional materials.First,a brief introduction is delivered for the structure,properties,and synthesis methods of MXenes.Then,we feed the readers the recent reports on the MXene-derived image sensors as artificial retinas,gas sensors,chemical biosensors,acoustic devices,and tactile sensors for electronic skin.Besides,the actuators of MXene-based composite are introduced.Eventually,future opportunities are given to MXene research based on the requirements of artificial intelligence and humanoid robot,which may induce prospects in accompanying healthcare and biomedical engineering applications.

Hybrid memristor-CMOS neurons for in-situ learning in fully hardware memristive spiking neural networks

Spiking neural network,inspired by the human brain,consisting of spiking neurons and plastic synapses,is a promising solution for highly efficient data processing in neuromorphic computing.Recently,memristor-based neurons and synapses are becoming intriguing candidates to build spiking neural networks in hardware,owing to the close resemblance between their device dynamics and the biological counterparts.However,the functionalities of memristor-based neurons are currently very limited,and a hardware demonstration of fully memristor-based spiking neural networks supporting in-situ learning is very challenging.Here,a hybrid spiking neuron combining a memristor with simple digital circuits is designed and implemented in hardware to enhance neuron functions.The hybrid neuron with memristive dynamics not only realizes the basic leaky integrate-and-fire neuron function but also enables the in-situ tuning of the connected synaptic weights.Finally,a fully hardware spiking neural network with the hybrid neurons and memristive synapses is experimentally demonstrated for the first time,and in-situ Hebbian learning is achieved with this network.This work opens up a way towards the implementation of spiking neurons,supporting in-situ learning for future neuromorphic computing systems.

Active tunable terahertz bandwidth absorber based on single layer graphene

In this paper,an active tunable terahertz bandwidth absorber based on single-layer graphene is proposed,which consists of a graphene layer,a photo crystal plate,and a gold substrate.When the Fermi energy(Ef)of graphene is 1.5 eV,the absorber shows high absorption in the range of 3.7 THz–8 THz,and the total absorption rate is 96.8%.By exploring the absorption mechanism of the absorber,the absorber shows excellent physical regulation.The absorber also shows good adjustability by changing the Efof graphene.This means that the absorber exhibits excellent tunability by adjusting the physical parameters and Efof the absorber.Meanwhile,the absorber is polarization independent and insensitive to the incident angle.The fine characteristics of the absorber mean that the absorber has superior application value in many fields such as biotechnology and space exploration.

Voltage-control oscillator based on Pt/C/NbO_x/TiN device with highly improved threshold switching performances

Oscillator is a common key component of electronic systems.The periodic signal produced by the oscillator is generally required in various applications,such as the electronic system clock,electronic neurons,and the true random number generator system[1-6].Capacitors and inductors are usually utilized to generate periodic waveforms in the traditional oscillator,which greatly reduces integration and cannot be packaged into chips[2].Oscillators based on a memristor have been proposed as a solution to these issues[7-14].The memristor has attracted great attention and has been widely applied in many fields,such as memory,com?puting,security,etc.

A flexible nickel phthalocyanine resistive random access memory with multi-level data storage capability

Metal phthalocyanine is considered one of the most promising candidates for the design and fabrication of flexible resistive random access memory(RRAM)devices due to its intrinsic flexibility and excellent functionality.However,performance degradation and the lack of multi-level capability,which can directly expand the storage capacity in one memory cell without sacrificing additional layout area,are the primary obstacles to the use of metal phthalocyanine RRAMs in information storage.Here,a flexible RRAM with pristine nickel phthalocyanine(Ni Pc)as the resistive layer is reported for multi-level data storage.Due to its high trap-concentration,the charge transport behavior of the device agrees well with classical space charge limited conduction controlled by traps,leading to an excellent performance,including a high on-off current ratio of 10^(7),a long-term retention of 10^(6)s,a reproducible endurance over6000 cycles,long-term flexibility at a bending strain of 0.6%,a write speed of 50 ns under sequential bias pulses and the capability of multi-level data storage with reliable retention and uniformity.