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1.
Nano Lett ; 2020 Mar 23.
Artigo em Inglês | MEDLINE | ID: mdl-32186388

RESUMO

To construct an artificial intelligence system with high efficient information integration and computing capability like the human brain, it is necessary to realize the biological neurotransmission and information processing in artificial neural network (ANN), rather than a single electronic synapse as most reports. Because the power consumption of single synaptic event is ∼10 fJ in biology, designing an intelligent memristors-based 3D ANN with energy consumption lower than femtojoule-level (e.g., attojoule-level) and faster operating speed than millisecond-level makes it possible for constructing a higher energy efficient and higher speed computing system than the human brain. In this paper, a flexible 3D crossbar memristor array is presented, exhibiting the multilevel information transmission functionality with the power consumption of 4.28 aJ and the response speed of 50 ns per synaptic event. This work is a significant step toward the development of an ultrahigh efficient and ultrahigh-speed wearable 3D neuromorphic computing system.

2.
Nanoscale ; 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32193525

RESUMO

As a well-known semiconductor that can catalyse the oxygen evolution reaction, TiO2 has been extensively investigated for its solar photoelectrochemical water properties. Unmodified TiO2 shows some issues, particularly with respect to its photoelectrochemical performance. In this paper, we present a strategy for the controlled deposition of controlled amounts of GaOxNy cocatalysts on TiO2 1D nanowires (TiO2@GaOxNy core-shell) using atomic layer deposition. We show that this modification significantly enhances the photoelectrochemical performance compared to pure TiO2 NW photoanodes. For our most active TiO2@GaOxNy core-shell nanowires with a GaOxNy thickness of 20 nm, a photocurrent density up to 1.10 mA cm-2 (at 1.23 V vs. RHE) under AM 1.5 G irradiation (100 mW cm-2) has been achieved, which is 14 times higher than that of unmodified TiO2 NWs. Furthermore, the band gap matching with TiO2 enhances the absorption of visible light over unmodified TiO2 and the facile oxygen vacancy formation after the deposition of GaOxNy also provides active sites for water activation. Density functional theory studies of model systems of GaOxNy-modified TiO2 confirm the band gap reduction, high reducibility and ability to activate water. The highly efficient and stable systems of TiO2@GaOxNy core-shell nanowires with ALD deposited GaOxNy demonstrate a good strategy for the fabrication of core-shell structures that enhance the photoelectrochemical performance of readily available photoanodes.

3.
ACS Appl Mater Interfaces ; 12(12): 14136-14144, 2020 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-32131586

RESUMO

Flexible pressure sensing is required for the excellent sensing performance and dexterous manipulation of the measured objects in their potential applications. Particularly, the ability to measure and discriminate the direction of force, contact surface, and contact location in real time is crucial for robotics with tactile feedback. Herein, a three-dimensional elastic porous carbon nanotube (CNT) sponge is synthesized by chemical vapor deposition, which is successfully applied in the piezoresistive sensor. In situ scanning electron microscopy study intuitively illustrates the characteristics that the microfibers of the CNT sponge distort and contact with each other under an external force. As a result, new conductive paths are created at the contact points between the CNT microfibers, which provides a basic sensing principle for a piezoresistive sensor. The CNT sponge-based sensor has an ultrahigh sensitivity in a wide pressure range (0-4 kPa for 4015.8 kPa-1), a rapid response time of 120 ms, and excellent durability over 5000 cycles. Moreover, a finlike flexible double-sided electronic skin (e-skin) is fabricated by a simple method to achieve force direction detection, which has potential applications in intelligent wearable devices and human-machine interaction.

4.
Artigo em Inglês | MEDLINE | ID: mdl-32003210

RESUMO

For the first time, we report the successful fabrication of well-behaved field-effect transistors based on Nb-doped ß-Ga2O3 nanobelts mechanically exfoliated from bulk single crystals. The exfoliated ß-Ga2O3 nanobelts were transferred onto a purified surface of the 110 nm SiO2/Si substrate. These Nb-doped devices showed excellent electrical performance such as an ultrasmall cutoff current of ∼10 fA, a high current on/off ratio of >108, and a quite steep subthreshold swing (SS, ∼120 mV/decade). Furthermore, we investigated the temperature dependence down to 200 K, providing insightful information for its operation in a harsh environment. This work lays a foundation for wider application of Nb-doped ß-Ga2O3 in nano-electronics.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32096620

RESUMO

Preparation of reliable, stable, and highly responsive gas-sensing devices for the detection of acetone has been considered to be a key issue for the development of accurate disease diagnosis systems via exhaled breath. In this paper, novel CeO2 nanodot-decorated WO3 nanowires are successfully synthesized through a sequential hydrothermal and thermolysis process. Such CeO2 nanodot-decorated WO3 nanowires exhibited a remarkable enhancement in acetone-sensing performance based on a miniaturized micro-electromechanical system device, which affords high response (S = 1.30-500 ppb, 1.62-2.5 ppm), low detection limit (500 ppb), and superior selectivity toward acetone. The improved performance of the acetone sensor is likely to be originated from the fast carrier transportation of WO3 nanowires, the formation of WO3-CeO2 heterojunctions, and the existence of large amounts of oxygen vacancies in CeO2. The improved reaction thermodynamics and sensing mechanisms have also been revealed by the specific band alignment and X-ray photoelectron spectroscopy analysis.

6.
Artigo em Inglês | MEDLINE | ID: mdl-32100523

RESUMO

Substantial progress has been made in the experimental synthesis of large-area two-dimensional transition metal dichalcogenide (TMD) thin films in recent years. This has provided a solid basis to build non-planar structures to implement the unique electrical and mechanical properties of TMDs in various nanoelectronic and mechano-electric devices, which, however, has not yet been fully explored. In this work, we demonstrate the fabrication and characterization of MoS2 field-effect transistors (FETs) with an omega (Ω)-shaped gate. The FET is built based on the SiO2/MoS2 core-shell heterostructure integrated using atomic layer deposition (ALD) technique. The MoS2 thin film has been uniformly deposited by ALD as wrapping the SiO2 nanowire forming the channel region, which is further surrounded by the gate dielectric and the Ω-gate. The device has exhibited n-type behavior with effective switching comparable to the reference device with a planar MoS2 channel built on a SiO2/Si substrate. Our work opens up an attractive avenue to realize novel device structures utilizing synthetic TMDs, thereby broadening their potential application in future advanced nanoelectronics.

7.
J Colloid Interface Sci ; 568: 81-88, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-32088454

RESUMO

Development of high-performance ammonia (NH3) sensor is imperative for monitoring NH3 in the living environment. In this work, to obtain a high performance NH3 gas sensor, structurally well-defined WO3@SnO2 core shell nanosheets with a controllable thickness of SnO2 shell layer have been employed as sensing materials. The prepared core shell nanosheets were used to obtain a miniaturized gas sensor based on micro-electro-mechanical system (MEMS). By tuning the thickness of SnO2 layer via atomic layer deposition, a series of WO3@SnO2 core-shell nanosheets with tunable sensing properties were realized. Particularly, the sensor base on the fabricated WO3@SnO2 nanosheets with 20-nm SnO2 shell layer demonstrated superior gas sensing performance with the highest response (1.55) and selectivity toward 15 ppm NH3 at 200 °C. This remarkable enhancement of NH3 sensing ability could be ascribed to the formation of unique WO3-SnO2 core-shell heterojunction structure. The detailed mechanism was elucidated by the heterojunction-depletion model with the help of specific band alignment.

8.
Pharmacol Res ; 153: 104660, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31982489

RESUMO

Multidrug resistance (MDR) represents an obstacle in anti-cancer therapy. MDR is caused by multiple mechanisms, involving ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp), which reduces intracellular drug levels to sub-therapeutic concentrations. Therefore, sensitizing agents retaining effectiveness against apoptosis- or drug-resistant cancers are desired for the treatment of MDR cancers. The sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump is an emerging target to overcome MDR, because of its continuous expression and because the calcium transport function is crucial to the survival of tumor cells. Previous studies showed that SERCA inhibitors exhibit anti-cancer effects in Bax-Bak-deficient, apoptosis-resistant and MDR cancers, whereas specific P-gp inhibitors reverse the MDR phenotype of cancer cells by blocking efflux of chemotherapeutic agents. Here, we unraveled SERCA and P-gp as double targets of the triterpenoid, celastrol to reverse MDR. Celastrol inhibited both SERCA and P-gp to stimulate calcium-mediated autophagy and ATP depletion, thereby induced collateral sensitivity in MDR cancer cells. In vivo studies further confirmed that celastrol suppressed tumor growth and metastasis by SERCA-mediated calcium mobilization. To the best of our knowledge, our findings demonstrate collateral sensitivity in MDR cancer cells by simultaneous inhibition of SERCA and P-gp for the first time.

9.
Small ; 16(1): e1904369, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31769618

RESUMO

2D transition metal dichalcogenides (TMDs) based photodetectors have shown great potential for the next generation optoelectronics. However, most of the reported MoS2 photodetectors function under the photogating effect originated from the charge-trap mechanism, which is difficult for quantitative control. Such devices generally suffer from a poor compromise between response speed and responsivity (R) and large dark current. Here, a dual-gated (DG) MoS2 phototransistor operating based on the interface coupling effect (ICE) is demonstrated. By simultaneously applying a negative top-gate voltage (VTG ) and positive back-gate voltage (VBG ) to the MoS2 channel, the photogenerated holes can be effectively trapped in the depleted region under TG. An ultrahigh R of ≈105 A W-1 and detectivity (D*) of ≈1014 Jones are achieved in several devices with different thickness under Pin of 53 µW cm-2 at VTG = -5 V. Moreover, the response time of the DG phototransistor can also be modulated based on the ICE. Based on these systematic measurements of MoS2 DG phototransistors, the results show that the ICE plays an important role in the modulation of photoelectric performances. The results also pave the way for the future optoelectrical application of 2D TMDs materials and prompt for further investigation in the DG structured phototransistors.

10.
Adv Sci (Weinh) ; 6(20): 1901072, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31637163

RESUMO

The human memory system plays an indispensable role in oblivion, learning, and memorization. Implementing a memory system within electronic devices contributes an important step toward constructing a neuromorphic system that emulates advanced mental functions of the human brain. Given the complex time-tailoring requirement, integrating a human memory system into one system is a great challenge. Here, one van der Waals heterostructure with flexible time-tailoring ability is demonstrated, which can meet the high requirement of human memory system programming. By stacking volatile and nonvolatile function layers, all basic memory types, including sensory memory, short-term and long-term memory are integrated into the device and the transition between these memory types are flexible. Moreover, decision-making action and in situ result storage are also demonstrated. It is anticipated that the demonstrated time-tailoring system will support the model of a human memory system.

11.
ACS Appl Mater Interfaces ; 11(35): 32127-32134, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31403281

RESUMO

The issue of contacts between the electrode and channel layer is crucial for wide-bandgap semiconductors, especially the ß-Ga2O3 due to its ultra-large bandgap (4.6-4.9 eV). It affects the device performance greatly and thus needs special attention. In this work, the high-performance ß-Ga2O3 nanobelt field-effect transistors with Ohmic contact between multilayer metal stack Ti/Al/Ni/Au (30/120/50/50 nm) and unintentionally doped ß-Ga2O3 channel substrate have been fabricated. The formation mechanism of Ohmic contacts to ß-Ga2O3 under different annealing temperatures in an N2 ambient is systematically investigated by X-ray photoelectron spectroscopy. It is revealed that the oxygen vacancies at the interface of ß-Ga2O3/intermetallic compounds formed during rapid thermal annealing are believed to induce the good Ohmic contacts with low resistance. The contact resistance (Rc) between electrodes and unintentionally doped ß-Ga2O3 reduces to ∼9.3 Ω mm after annealing. This work points to the importance of contact engineering for future improved ß-Ga2O3 device performance and lays a solid foundation for the wider application of ß-Ga2O3 in electronics and optoelectronics.

12.
Nat Nanotechnol ; 14(7): 662-667, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31133664

RESUMO

The need for continuous size downscaling of silicon transistors is driving the industrial development of strategies to enable further footprint reduction1,2. The atomic thickness of two-dimensional materials allows the potential realization of high-area-efficiency transistor architectures. However, until now, the design of devices composed of two-dimensional materials has mimicked the basic architecture of silicon circuits3-6. Here, we report a transistor based on a two-dimensional material that can realize photoswitching logic (OR, AND) computing in a single cell. Unlike the conventional transistor working mechanism, the two-dimensional material logic transistor has two surface channels. Furthermore, the material thickness can change the logic behaviour-the architecture can be flexibly expanded to achieve in situ memory such as logic computing and data storage convergence in the same device. These devices are potentially promising candidates for the construction of new chips that can perform computing and storage with high area-efficiency and unique functions.

13.
Nanoscale Res Lett ; 14(1): 102, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30877593

RESUMO

Artificial synapses are the fundamental of building a neuron network for neuromorphic computing to overcome the bottleneck of the von Neumann system. Based on a low-temperature atomic layer deposition process, a flexible electrical synapse was proposed and showed bipolar resistive switching characteristics. With the formation and rupture of ions conductive filaments path, the conductance was modulated gradually. Under a series of pre-synaptic spikes, the device successfully emulated remarkable short-term plasticity, long-term plasticity, and forgetting behaviors. Therefore, memory and learning ability were integrated to the single flexible memristor, which are promising for the next-generation of artificial neuromorphic computing systems.

14.
Nanoscale Res Lett ; 14(1): 76, 2019 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-30830476

RESUMO

For advanced Cu interconnect technology, Co films have been widely investigated to serve as the liner and seed layer replacement because of a better wettability to Cu than Ta. In this article, the Co films are grown by plasma-enhanced atomic layer deposition using Co(EtCp)2 as a precursor, and the influences of process parameters on the characteristics of the Co films are elaborately investigated. The results indicate that the process window is 125-225 °C with a growth rate of ~ 0.073 Å/cycle. That is to say, the connection of Et group to Cp ligand can enable a stable film growth at 125 °C, while the corresponding temperature must be higher than 200 °C in terms of Co(Cp)2 and Co(MeCp)2. The deposited films contain N and O elements besides dominant Co and C. Furthermore, the prolongation of the NH3 pulse time significantly enhances the conductivity of the Co film and a low resistivity of 117 µΩ cm can be achieved with a NH3 pulse time of 40 s. The root mean square roughness shows a smaller variation with the deposition temperature and maintains a low value of ~ 0.3 nm, indicative of a flat Co film.

15.
Nanoscale Res Lett ; 14(1): 53, 2019 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-30742246

RESUMO

For metal-insulator-metal (MIM) capacitors applicated in the fields of RF, DRAM, and analog/mixed-signal integrated circuits, a high capacitance density is imperative with the downscaling of the device feature size. In this work, the microwave annealing technique is investigated to enhance the dielectric characteristics of Al2O3/ZrO2/Al2O3 based MIM capacitors. The results show that the permittivity of ZrO2 is increased to 41.9 (~ 40% enhanced) with a microwave annealing at 1400 W for 5 min. The substrate temperature is lower than 400 °C, which is compatible with the back end of line process. The leakage current densities are 1.23 × 10-8 and 1.36 × 10-8 A/cm2 for as-deposited sample and 1400 W sample, respectively, indicating that the leakage property is not deteriorated. The conduction mechanism is confirmed as field-assisted tunneling.

16.
Nanoscale Res Lett ; 14(1): 51, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30734146

RESUMO

With Moore's law closing to its physical limit, traditional von Neumann architecture is facing a challenge. It is expected that the computing in-memory architecture-based resistive random access memory (RRAM) could be a potential candidate to overcome the von Neumann bottleneck problem of traditional computers [Backus, J, Can programming be liberated from the von Neumann style?, 1977]. In this work, HfAlOx-based RRAM which is compatible with CMOS technology was fabricated by an atomic layer deposition (ALD) process. Metal Ag and TaN are selected as top electrodes (TE). Experiments show that the Ag/HfAlOx/Pt device has demonstrated advantages as a memory-computing device because of the low set voltage (0.33~0.6 V) which means low power consumption and good uniformity. Based on a Ag/HfAlOx/Pt structure, IMP logic was implemented at high speed by applying a 100-ns high-frequency low-voltage pulse (0.3 V and 0.6 V). After two steps of IMP implementation, NAND can also be obtained.

17.
Small ; 15(5): e1803876, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30624032

RESUMO

Due to their advantages compared with planar structures, rolled-up tubes have been applied in many fields, such as field-effect transistors, compact capacitors, inductors, and integrative sensors. On the other hand, because of its perfect insulating nature, ultrahigh mechanical strength and atomic thickness property, 2D hexagonal boron nitride (h-BN) is a very suitable material for rolled-up memory applications. In this work, a tubular 3D resistive random access memory (RRAM) device based on rolled-up h-BN tube is realized, which is achieved by self-rolled-up technology. The tubular RRAM device exhibits bipolar resistive switching behavior, nonvolatile data storage ability, and satisfactorily low programming current compared with other 2D material-based RRAM devices. Moreover, by releasing from the substrate, the footprint area of the tubular device is reduced by six times. This tubular RRAM device has great potential for increasing the data storage density, lowering the power consumption, and may be applied in the fields of rolled-up systems and sensing-storage integration.

18.
Adv Mater ; 31(11): e1808035, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30687966

RESUMO

Due to the large gap in timescale between volatile memory and nonvolatile memory technologies, quasi-nonvolatile memory based on 2D materials has become a viable technology for filling the gap. By exploiting the elaborate energy band structure of 2D materials, a quasi-nonvolatile memory with symmetric ultrafast write-1 and erase-0 speeds and long refresh time is reported. Featuring the 2D semifloating gate architecture, an extrinsic p-n junction is used to charge or discharge the floating gate. Owing to the direct injection or recombination of charges from the floating gate electrode, the erasing speed is greatly enhanced to nanosecond timescale. Combined with the ultrafast write-1 speed, symmetric ultrafast operations on the nanosecond timescale are achieved, which are ≈106 times faster than other memories based on 2D materials. In addition, the refresh time after a write-1 operation is 219 times longer than that of dynamic random access memory. This performance suggests that quasi-nonvolatile memory has great potential to decrease power consumption originating from frequent refresh operations, and usher in the next generation of high-speed and low-power memory technology.

19.
Nanotechnology ; 30(17): 174002, 2019 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-30641493

RESUMO

Chemical vapor deposition synthesis of semiconducting transition metal dichalcogenides (TMDs) offers a new route to build next-generation semiconductor devices. But realization of continuous and uniform multilayer (ML) TMD films is still limited by their specific growth kinetics, such as the competition between surface and interfacial energy. In this work, a layer-by-layer vacuum stacking transfer method is applied to obtain uniform and non-destructive ML-MoS2 films. Back-gated field effect transistor (FET) arrays of 1L- and 2L-MoS2 are fabricated on the same wafer, and their electrical performances are compared. We observe a significant increase of field-effect mobility for 2L-MoS2 FETs, up to 32.5 cm2 V-1 s-1, which is seven times higher than that of 1L-MoS2 (4.5 cm2 V-1 s-1). Then we also fabricated 1L-, 2L-, 3L-, and 4L-MoS2 FETs to further investigate the thickness-dependent characteristics of transferred ML-MoS2. Measurement results show a higher mobility but a smaller current on/off ratio as the layer number increases, suggesting that a balance between mobility and current on/off ratio can be achieved in 2L- and 3L-MoS2 FETs. Dual-gated structure is also investigated to demonstrate an improved electrostatic control of the ML-MoS2 channel.

20.
Adv Mater ; 31(3): e1806227, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30485567

RESUMO

Just as biological synapses provide basic functions for the nervous system, artificial synaptic devices serve as the fundamental building blocks of neuromorphic networks; thus, developing novel artificial synapses is essential for neuromorphic computing. By exploiting the band alignment between 2D inorganic and organic semiconductors, the first multi-functional synaptic transistor based on a molybdenum disulfide (MoS2 )/perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) hybrid heterojunction, with remarkable short-term plasticity (STP) and long-term plasticity (LTP), is reported. Owing to the elaborate design of the energy band structure, both robust electrical and optical modulation are achieved through carriers transfer at the interface of the heterostructure, which is still a challenging task to this day. In electrical modulation, synaptic inhibition and excitation can be achieved simultaneously in the same device by gate voltage tuning. Notably, a minimum inhibition of 3% and maximum facilitation of 500% can be obtained by increasing the electrical number, and the response to different frequency signals indicates a dynamic filtering characteristic. It exhibits flexible tunability of both STP and LTP and synaptic weight changes of up to 60, far superior to previous work in optical modulation. The fully 2D MoS2 /PTCDA hybrid heterojunction artificial synapse opens up a whole new path for the urgent need for neuromorphic computation devices.


Assuntos
Materiais Biomiméticos , Transistores Eletrônicos , Anidridos , Biomimética , Dissulfetos , Desenho de Equipamento , Humanos , Molibdênio , Inibição Neural , Plasticidade Neuronal , Neurônios/fisiologia , Perileno/análogos & derivados , Sinapses/fisiologia , Transmissão Sináptica
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