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A dual-function memory with complementary metal oxide semiconductor (CMOS) compatibility is presented with the feasibility of future embedded applications. The self-selective memory composed of bilayer oxide stacks is presented with the immunity of sneak-path current and improved thermal stability for the high storage class memory array application. Meanwhile, the one-time programmable memory is realized by the identical bilayer structure which has improved the yield of dielectric-fuse phenomena by increasing the operating temperature up to 423 K. The physical mechanisms and modeling are investigated with experimental and simulated results. Our results provide pathfinding of high density, CMOS back-end-of-line integration capability, land ow power multi-functionality in the future embedded applications.

This study demonstrated the successful epitaxy of La-SrSnO3/BaTiO3 on SrTiO3-buffered Si (001) with ALD-deposited La-SrSnO3 and explored the optimization of post-annealing to enhance the capacitance properties of heterostructure.

Path to another drug against COVID-19 The rapid development of vaccines has been crucial in battling the ongoing COVID-19 pandemic. However, access challenges remain, breakthrough infections occur, and emerging variants present increased risk. Developing antiviral therapeutics is therefore a high priority for the treatment of COVID-19. Some drug candidates in clinical trials act against the viral RNA-dependent RNA polymerase, but there are other viral enzymes that have been considered good targets for inhibition by drugs. Owen et al . report the discovery and characterization of a drug against the main protease involved in the cleavage of polyproteins involved in viral replication. The drug, PF-07321332, can be administered orally, has good selectivity and safety profiles, and protects against infection in a mouse model. In a phase 1 clinical trial, the drug reached concentrations expected to inhibit the virus based on in vitro studies. It also inhibited other coronaviruses, including severe acute respiratory syndrome coronavirus 1 and Middle East respiratory syndrome coronavirus, and could be in the armory against future viral threats. —VV

Transition-metal dichalcogenides (TMDs) have attracted intense research interest for a broad range of device applications. Atomic layer deposition (ALD), a CMOS compatible technique, can enable the preparation of high-quality TMD films on 8 to 12 in. wafers for large-scale circuit integration. However, the ALD growth mechanisms are still not fully understood. In this work, we systematically investigated the growth mechanisms for WS2 and found them to be strongly affected by nucleation density and film thickness. Transmission electron microscope imaging reveals the coexistence and competition of lateral and vertical growth mechanisms at different growth stages, and the critical thicknesses for each mechanism are obtained. The in-plane lateral growth mode dominates when the film thickness remains less than 5.6 nm (8 layers), while the vertical growth mode dominates when the thickness is greater than 20 nm. From the resulting understanding of these growth mechanisms, the conditions for film deposition were optimized and a maximum grain size of 108 nm was achieved. WS2-based field-effect transistors were fabricated with electron mobility and on/off current ratio up to 3.21 cm2 V-1 s-1 and 105, respectively. Particularly, this work proves the capability of synthesis of TMD films in a wafer scale with excellent controllability of thickness and morphology, enabling many potential applications other than transistors, such as nanowire- or nanosheet-based supercapacitors, batteries, sensors, and catalysis.

The dual-functional resistive random-access memories (RRAMs) are presented as the nonvolatile switching (NVS) memory and volatile threshold switching (VTS) devices by changing the operation polarities in the identical memory device. The built-in nonlinearity is demonstrated of~102 in NVS for the selectorless memristor, and the selectivity is of ~103 in volatile switching for the selector device application. The crossbar array of HfOx/graphite stacks is implementing an improved read margin with nonvolatile selectorless unit. In comparison with current memory technology, the dual-functional hybrid selectorless memristor in this work is presented by low thermal budget, high ON– OFF ratio (~102), good self-selectivity in selectorless memory (~1012), high selectivity in selection device (~103), and low switching voltage for both memory and selection devices. The dual-functional switching behaviors not only provide the effective ways to 3-D integration for storage class memory, but also for emerging computing paradigms such as in-memory computing and neuromorphic computing applications.

Chiral cyclobutanes are components of numerous bioactive natural products, and consequently, they have also gained significant attention in medicinal chemistry. Optically enriched cyclobutylboronat...

Molybdenum trioxide (MoO

A mild, direct C-H arylation of 1-substituted tetrazoles to 5-aryltetrazoles is developed using a Pd/Cu cocatalytic system with readily available aryl bromides. The methodology avoids late-stage usage of azides and tolerates a wide range of functionalities.

Bilayer selectorless resistive random-access memories (RRAM) have been demonstrated by utilizing the intrinsic nonlinear resistive switching (RS) characteristics, without additional transistor or a selector integration. The bilayer structures, i.e. high-k layer/low-k layer stacks, are highly scalable while suppressing the sneak path currents (SPC) and reading error in the crossbar RRAM array. The nonlinearity (NL) modulation is also investigated by different operating schemes, and a multilevel cell application is demonstrated with the current-sweep method. The results provide additional insights into the development and optimization of bilayer selectorless RRAMs with high nonlinearity, good memory window, and low switching energy (∼ 40 pJ/bit), which enable the high-density storage and low-power crossbar array memory applications.

MoS2 has been reported to exhibit a resistive switching phenomenon in a vertical metal–insulator–metal (MIM) structure and has attracted much attention due to its ultra-thin active layer thickness. Here, the resistance evolutions in the high resistance state (HRS) and low resistance state (LRS) are investigated under constant voltage stress (CVS) or constant current stress (CCS) on MoS2 resistive switching devices. Interestingly, compared with bulk transition metal oxides (TMO), MoS2 exhibits an opposite characteristic in the fresh or pre-RESET device in the “HRS” wherein the resistance will increase to an even higher resistance after applying CVS, a unique phenomenon only accessible in 2D-based resistive switching devices. It is inferred that instead of in the highest resistance state, the fresh or pre-RESET devices are in an intermediate state with a small amount of Au embedded in the MoS2 film. Inspired by the capability of both bipolar and unipolar operation, positive and negative CVS measurements are performed and show similar characteristics. In addition, it is observed that the resistance state transition is faster when using higher electric stress. Numerical simulations have been performed to study the temperature effect with small-area integration capability. These results can be explained by a modified conductive-bridge-like model based on Au migration, uncovering the switching mechanisms in the ultrathin 2D materials and inspiring future studies in this area.

Cyclobutane rings are important in medicinal chemistry, yet few enantioselective methods exist to access this scaffold. In particular, cyclobutylboronates are receiving increasing attention in the literature due to the synthetic versatility of alkylboronic esters and the increasing role of boronic acids in drug discovery. Herein, a conjugate borylation of α-alkyl,β-aryl/alkyl cyclobutenones is reported leading to the first synthesis of enantioenriched tertiary cyclobutylboronates. Cyclobutanones with two stereogenic centers are obtained in good to high yield, with high enantioselectivity and diastereoselectivity. Vital to this advance are the development of a novel approach to α,β unsymmetrically disubstituted cyclobutenone substrates and the use of a high-throughput chiral ligand screening platform. The synthetic utility of both the boronic ester and ketone functionalities is displayed, with remarkable chemoselectivity for either group being possible in this small ring scaffold.

The worldwide outbreak of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic. Alongside vaccines, antiviral therapeutics are an important part of the healthcare response to countering the ongoing threat presented by COVID-19. Here, we report the discovery and characterization of PF-07321332, an orally bioavailable SARS-CoV-2 main protease inhibitor with in vitro pan-human coronavirus antiviral activity and excellent off-target selectivity and in vivo safety profiles. PF-07321332 has demonstrated oral activity in a mouse-adapted SARS-CoV-2 model and has achieved oral plasma concentrations exceeding the in vitro antiviral cell potency in a phase 1 clinical trial in healthy human participants.

Resistive random-access memory (RRAM) devices have drawn increasing interest for the simplicity of its structure, low power consumption and applicability to neuromorphic computing. By combining analog computing and data storage at the device level, neuromorphic computing system has the potential to meet the demand of computing power in applications such as artificial intelligence (AI), machine learning (ML) and Internet of Things (IoT). Monolayer rhenium diselenide (ReSe2), as a two-dimensional (2D) material, has been reported to exhibit non-volatile resistive switching (NVRS) behavior in RRAM devices with sub-nanometer active layer thickness. In this paper, we demonstrate stable multiple-step RESET in ReSe2 RRAM devices by applying different levels of DC electrical bias. Pulse measurement has been conducted to study the neuromorphic characteristics. Under different height of stimuli, the ReSe2 RRAM devices have been found to switch to different resistance states, which shows the potentiation of synaptic applications. Long-term potentiation (LTP) and depression (LTD) have been demonstrated with the gradual resistance switching behaviors observed in long-term plasticity programming. A Verilog-A model is proposed based on the multiple-step resistive switching behavior. By implementing the LTP/LTD parameters, an artificial neural network (ANN) is constructed for the demonstration of handwriting classification using Modified National Institute of Standards and Technology (MNIST) dataset.

Two-dimensional materials have been discovered to exhibit non-volatile resistive switching (NVRS) phenomenon. In our work, we reported the universal NVRS behavior in a dozen metal dichalcogenides, featuring low switching voltage, large on/off ratio, fast switching speed and forming free characteristics. A unique conductive-point random access memory (CPRAM) effect is used to explain the switching mechanisms, supported by experimental results from current-sweep measurements., 3 pages, 5 figures, IEEE conference(2021 5th EDTM)

Transition-metal dichalcogenides (TMDs) have attracted intense research interest for a broad range of device applications. Atomic layer deposition (ALD), a CMOS compatible technique, can enable the preparation of high-quality TMD films on 8 to 12 in. wafers for large-scale circuit integration. However, the ALD growth mechanisms are still not fully understood. In this work, we systematically investigated the growth mechanisms for WS

The worldwide outbreak of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become an established global pandemic. Alongside vaccines, antiviral therapeutics are an important part of the healthcare response to counter the ongoing threat presented by COVID-19. Here, we report the discovery and characterization of PF-07321332, an orally bioavailable SARS-CoV-2 main protease inhibitor with in vitro pan-human coronavirus antiviral activity, and excellent off-target selectivity and in vivo safety profiles. PF-07321332 has demonstrated oral activity in a mouse- adapted SARS-CoV-2 model and has achieved oral plasma concentrations exceeding the in vitro antiviral cell potency, in a phase I clinical trial in healthy human participants. ClinicalTrials.gov Identifier: NCT04756531 One-Sentence Summary PF-07321332 is disclosed as a novel, orally active, investigational small-molecule inhibitor of the SARS-CoV-2 main protease, which is being evaluated in clinical trials for the treatment of COVID-19.

In2O3-based metal-oxide-semiconductor channel materials are attractive for thin-film transistors and novel back-end-of-line (BEOL) compatible devices and have attracted intensive research activities in recent years. However, several challenges remain, such as the ultrahigh electron density and the nature of polycrystalline films. To overcome these issues, here in this work, we demonstrated an in situ semi-insulating doping method of In2O3 via atomic layer deposition and fabricated the indium-aluminum-oxide (IAO) transistors. The controllable concentration of Al enables an on-current of 1.8 μA/ μm with the cycle ratio at In2O3:Al2O3 (10:1), mobility, and subthreshold swing of the transistor are 8.7 cm2/V s, and 203 mV/dec. The threshold voltage (Vt) is adjustable by varying Al concentrations, shifting to negative bias with a higher concentration of Al. The IAO-based transistor presents many advantages, including excellent on/off ratio and high mobility, making it ideal for many applications, such as display panels and low-power BEOL integrations.

For the first time, the impact of temperature instability of resistive memory switching on potential neuromorphic computing applications has been extensively studied using eNVM-R and eNVM-M technologies developed on Intel 22FFL process. The reliability risk assessment shows that the effects of ambient temperature (e.g. resistance or conductance shifting with varying temperature) can lead to potential degradation of the neural network accuracy. Our results provide additional insight into device-level physical models and circuit-level design guidance for potential AI hardware applications.

Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS 2 films and in situ Nb-doped p-type WS 2 films were synthesized through atomic layer deposition (ALD) on 8-inch α -Al 2 O 3 /Si wafers, 2-inch sapphire, and 1 cm 2 GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS 2 n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS 2 n-FET are as high as 10 5 and 6.85 cm 2 V -1 s -1 , respectively. In WS 2 p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm 2 V -1 s -1 , respectively. The p-n structure based on n- and p- type WS 2 films was proved with a 10 4 rectifying ratio. The realization of controllable in situ Nb-doped WS 2 films paved a way for fabricating wafer-scale complementary WS 2 FETs.

Hexagonal boron nitride (hBN) has a large bandgap, high phonon energies and an atomically smooth surface absent of dangling bonds. As a result, it has been widely used as a dielectric to investigate electron physics in two-dimensional heterostructures and as a dielectric in the fabrication of two-dimensional transistors and optoelectronic devices. Here we show that hBN can be used to create analogue switches for applications in communication systems across radio, 5G and terahertz frequencies. Our approach relies on the non-volatile resistive switching capabilities of atomically thin hBN. The switches are composed of monolayer hBN sandwiched between two gold electrodes and exhibit a cutoff-frequency figure of merit of around 129 THz with a low insertion loss (≤0.5 dB) and high isolation (≥10 dB) from 0.1 to 200 GHz, as well as a high power handling (around 20 dBm) and nanosecond switching speeds, metrics that are superior to those of existing solid-state switches. Furthermore, the switches are 50 times more efficient than other non-volatile switches in terms of a d.c. energy-consumption metric, which is an important consideration for ubiquitous mobile systems. We also illustrate the potential of the hBN switches in a communication system with an 8.5 Gbit s–1 data transmission rate at 100 GHz with a low bit error rate under 10−10. Resistive switching in atomically thin sheets of hexagonal boron nitride can be used to create analogue switches for applications in communication systems across radio, 5G and terahertz frequencies.

Recently, various two-dimensional materials have been reported to exhibit non-volatile resistance switching phenomenon. The atomristors, featuring memristor effect in atomically thin nanomaterials such as monolayer transition metal dichalcogenides and hexagonal boron nitride, have drawn much attention due to the extremely thin active layer thickness with the advantages of forming-free characteristic, large on/off resistance ratio and fast switching speed. To investigate the switching mechanisms in the 2D monolayers, we introduced an electrical characterization method by current sweeping to illustrate the detailed information hidden in the commonly used voltage-sweep curves. Multiple transition steps have been observed in the SET process of MoS

MoS

The ever‐increasing processing power demands of digital computers cannot continue to be fulfilled indefinitely unless there is a paradigm shift in computing. Neuromorphic computing, which takes inspiration from the highly parallel, low‐power, high‐speed, and noise‐tolerant computing capabilities of the brain, may provide such a shift. Many researchers from across academia and industry have been studying materials, devices, circuits, and systems, to implement some of the functions of networks of neurons and synapses to develop neuromorphic computing platforms. These platforms are being designed using various hardware technologies, including the well‐established complementary metal‐oxide semiconductor (CMOS), and emerging memristive technologies such as SiOx‐based memristors. Herein, recent progress in CMOS, SiOx‐based memristive, and mixed CMOS‐memristive hardware for neuromorphic systems is highlighted. New and published results from various devices are provided that are developed to replicate selected functions of neurons, synapses, and simple spiking networks. It is shown that the CMOS and memristive devices are assembled in different neuromorphic learning platforms to perform simple cognitive tasks such as classification of spike rate‐based patterns or handwritten digits. Herein, it is envisioned that what is demonstrated is useful to the unconventional computing research community by providing insights into advances in neuromorphic hardware technologies.

Since the discovery of graphene, two-dimensional (2D) materials have drawn much attention as a promising candidate in the next-generation electron devices, optoelectronics and bioelectronics1, 2. Over the last few years, researchers have proved the existence of the non-volatile resistance switching (NVRS) behavior in various 2D materials, including graphene oxide, functionalized MoS 2 , partially degraded black phosphorus and multi-layer hexagonal boron-nitride (h-BN), etc.3–6, where the resistance can be switched between a high-resistance state (HRS) and a low-resistance state (LRS) and maintained for a long time without power supply 7. In 2015, Sangwan et al. discovered that grain boundaries in single-layer MoS 2 can produce NVRS based on planar (horizontal) structure8. However, the planar structure without 3D stacking ability has the limitation of low integration density. Therefore, to overcome vertical scaling obstacle in NVRS based on conventional metal-insulator-metal (MIM) structure, it is desired to find out the thinnest materials that can produce the resistance switching behavior based on vertical device structure. Recently, we discovered that NVRS phenomenon is accessible in a variety of single-layer transition metal dichalcogenides (TMDs) and single-layer h-BN in vertical MIM configuration9–12. Compared with other 2D material-based NVRS devices, single-layer h-BN has only one atomic layer and ∼0.33 nm in thickness, which is the thinnest active layer in non-volatile resistance memory. These devices can be collectively labelled as “atomristor”, which means the memristor effect in atomically thin nanomaterials. The TMDs and h-BN atomristors have been studied using a crossbar or a litho-free & transfer-free structure, demonstrating forming-free switching with large on/off ratio (up to 6 orders of magnitude) and low switching voltage (down to 15 dB) up to 100 GHz. The operating frequencies cover the RF, 5G, and mm-wave bands, making this a promising low-power switch for diverse communication and connectivity front-end systems. The results of this work indicate a potential universal resistive switching behavior in 2D monolayers, which is applicable to memory technology, neuromorphic computing, RF switch and flexible electronics.