Reconfigurable Logic-in-Memory Computing Based on a Polarity-Controllable Two-Dimensional Transistor.

Logic-in-memory architecture holds great promise to meet the high-performance and energy-efficient requirements of data-intensive scenarios. Two-dimensional compacted transistors embedded with logic functions are expected to extend Moore's law toward advanced nodes. Here we demonstrate that a WSe2/h-BN/graphene based middle-floating-gate field-effect transistor can perform under diverse current levels due to the controllable polarity by the control gate, floating gate, and drain voltages. Such electrical tunable characteristics are employed for logic-in-memory architectures and can behave as reconfigurable logic functions of AND/XNOR within a single device. Compared to the conventional devices like floating-gate field-effect transistors, our design can greatly decrease the consumption of transistors. For AND/NAND, it can save 75% transistors by reducing the transistor number from 4 to 1; for XNOR/XOR, it is even up to 87.5% with the number being reduced from 8 to 1.

Chemical Dopant-Free Controlled MoTe2/MoSe2 Heterostructure toward a Self-Driven Photodetector and Complementary Logic Circuits.

Two-dimensional (2D) van der Waals heterostructures based on transition metal dichalcogenides are expected to be unique building blocks for next-generation nanoscale electronics and optoelectronics. The ability to control the properties of 2D heterostructures is the key for practical applications. Here, we report a simple way to fabricate a high-performance self-driven photodetector based on the MoTe2/MoSe2 p-n heterojunction, in which the hole-dominated transport polarity of MoTe2 is easily achieved via a straightforward thermal annealing treatment in air without any chemical dopants or special gases needed. A high photoresponsivity of 0.72 A W-1, an external quantum efficiency up to 41.3%, a detectivity of 7 × 1011 Jones, and a response speed of 120 µs are obtained at zero bias voltage. Additionally, this doping method is also utilized to realize a complementary inverter with a voltage gain of 24. By configuring 2D p-MoTe2 and n-MoSe2 on demand, logic functions of NAND and NOR gates are also accomplished successfully. These results present a significant potential toward future larger-scale heterogeneously integrated 2D electronics and optoelectronics.

Ambipolar 2D Semiconductors and Emerging Device Applications.

With the rise of 2D materials, new physics and new processing techniques have emerged, triggering possibilities for the innovation of electronic and optoelectronic devices. Among them, ambipolar 2D semiconductors are of excellent gate-controlled capability and distinctive physical characteristic that the major charge carriers can be dynamically, reversibly and rapidly tuned between holes and electrons by electrostatic field. Based on such properties, novel devices, like ambipolar field-effect transistors, light-emitting transistors, electrostatic-field-charging PN diodes, are developed and show great advantages in logic and reconfigurable circuits, integrated optoelectronic circuits, and artificial neural network image sensors, enriching the functions of conventional devices and bringing breakthroughs to build new architectures. This review first focuses on the basic knowledge including fundamental principle of ambipolar semiconductors, basic material preparation techniques, and how to obtain the ambipolar behavior through electrical contact engineering. Then, the current ambipolar 2D semiconductors and their preparation approaches and main properties are summarized. Finally, the emerging new device structures are overviewed in detail, along with their novel electronic and optoelectronic applications. It is expected to shed light on the future development of ambipolar 2D semiconductors, exploring more new devices with novel functions and promoting the applications of 2D materials.

2D electric-double-layer phototransistor for photoelectronic and spatiotemporal hybrid neuromorphic integration.

The hardware implementation of neuromorphic computing has attracted growing interest as a promising candidate for confronting the bottleneck of traditional von Neumann computers. However, most previous reports are focusd on emulating the synaptic behaviors by a mono-mode using an electric-driving or photo-driving approach, resulting in a big challenge to synchronously handle the natural photoelectric information. Herein, we report a multifunctional photoelectronic hybrid-integrated synaptic device based on the electric-double-layer (EDL) MoS2 phototransistor. Interestingly, the electric MoS2 synapse exhibits a potentiation filtering effect, while the photonic counterpart can implement both potentiation and depression filtering effects. Most importantly, for the first time, photoelectronic and spatio-temporal four-dimensional (4D) hybrid integration was successfully demonstrated by the synergic interplay between photonic and electric stimuli within a single MoS2 synapse. An energy band model is proposed to further understand such a photoelectronic and spatio-temporal 4D hybrid coupling mechanism. These results might provide an alternative solution for the size-scaling and intellectualization campaign of the post-Moore era, and for more sophisticated photoelectronic hybrid computing in the emerging neuromorphic nanoelectronics.

Transient security transistors self-supported on biodegradable natural-polymer membranes for brain-inspired neuromorphic applications.

Transient electronics, a new generation of electronics that can physically or functionally vanish on demand, are very promising for future "green" security biocompatible electronics. At the same time, hardware implementation of biological synapses is highly desirable for emerging brain-like neuromorphic computational systems that could look beyond the conventional von Neumann architecture. Here, a hardware-security physically-transient bidirectional artificial synapse network based on a dual in-plane-gate Al-Zn-O neuromorphic transistor was fabricated on free-standing laterally-coupled biopolymer electrolyte membranes (sodium alginate). The excitatory postsynaptic current, paired-pulse-facilitation, and temporal filtering characteristics from high-pass to low-pass transition were successfully mimicked. More importantly, bidirectional dynamic spatiotemporal learning rules and neuronal arithmetic were also experimentally demonstrated using two lateral in-plane gates as the presynaptic inputs. Most interestingly, excellent physically-transient behavior could be achieved with a superfast water-soluble speed of only ∼120 seconds. This work represents a significant step towards future hardware-security transient biocompatible intelligent electronic systems.

Coplanar Multigate MoS2 Electric-Double-Layer Transistors for Neuromorphic Visual Recognition.

Spatial coordinate and visual orientation recognition in cortical cells play important roles in the visual system. Herein, spatiotemporally processed visual neurons are mimicked by a facile coplanar multigate two-dimensional (2D) MoS2 electric-double-layer transistor with proton-conducting poly(vinyl alcohol) electrolytes as laterally coupled gate dielectrics. Fundamental neuromorphic behaviors, e.g., excitatory postsynaptic current and paired-pulse facilitation, were successfully mimicked. For the first time, a proof-of-principle artificial visual neural network system for mimicking spatiotemporal coordinate and orientation recognition was experimentally demonstrated in such devices. The experimental results provide a promising opportunity for adding intelligent spatiotemporally-processed functions in emerging brain-like neuromorphic nanoelectronics.