Graphene Bridge Heterostructure Devices for Negative Differential Transconductance Circuit Applications

Design Principles of Flexible Substrates and Polymer Electrolytes for Flexible Zinc Ion Batteries

Flexible ZIBs are gaining significant attention as a cost-effective and inherently safe energy storage technology with promising applications in next-generation flexible and wearable devices. The rising demand for flexible electronics has spurred the advancement of flexible batteries. However, the widespread adoption of liquid electrolytes in zinc-ion batteries has been hindered by persistent challenges, including liquid leakage, water evaporation, and parasitic water-splitting reactions, which pose significant obstacles to commercialization. Free-standing flexible substrates and solid-state polymer electrolytes are key to enhancing the energy density, ionic conductivity, power density, mechanical strength, and flexibility of ZIBs. Herein, this review highlights recent progress and strategies for developing high-efficiency flexible ZIBs as energy storage systems, focusing on advancements in flexibility (transitioning from rigid to flexible), electrolytes (shifting from liquid to solid), adaptability (from non-portable to portable designs), and the transition from laboratory research to practical industrial applications. Critical assessments of advanced modification approaches for flexible substrates and solid-state electrolytes are presented, emphasizing their role in achieving safe, flexible, stretchable, wearable, and self-healing ZIBs. Finally, future research directions and development strategies for designing effective solid-state polymer electrolytes and flexible substrates for next-generation flexible ZIBs are discussed.

Optical Modification of TMD Heterostructures

Optical modification is a fast, cost-effective, and scalable approach to tailoring the physical properties of two-dimensional (2D) materials for various applications. However, most previous efforts have focused on modifying individual 2D materials, which fails to utilize the method to its fullest potential. In this paper, heterostructures composed of hBN-capped molybdenum ditelluride (MoTe2) and molybdenum disulfide (MoS2) are optically modified with a continuous wave laser. The process simultaneously thins MoS2 and induces clustering of tellurium atoms from the ablated MoTe2. These structural changes result in significant enhancements of the physical properties, including a 43-fold increase in MoS2 photoluminescence and the transformation of the heterojunction into an anti-ambipolar transistor. These findings highlight a previously unutilized pathway to tune the heterostructure properties for applications in novel electronics and optoelectronics.

Applications of a ZnO-Te Antiambipolar Switch for Drastic Power and Area Scaling

Combinations of n- and p-type semiconductors (with thicknesses of a few nanometers or ultrathin) deposited at low temperatures are creating new opportunities for novel devices and circuits. We demonstrate an antiambipolar switch (AAS) device using a heterojunction comprising extremely thin ZnO and Te layers operating at a complementary metal-oxide semiconductor (CMOS)-compatible bias (∼1.2 V) with a high peak-to-valley ratio (∼104). The entire process was performed at a full wafer scale with a low thermal budget at temperatures below 150 °C. The device count and area of the binary-to-ternary converter designed with this device were reduced by ∼95% and ∼97%, respectively. In addition, we demonstrate a few examples of binary-ternary logic circuits to show that the system complexity and computing efficiency of the binary CMOS architecture can be dramatically improved by easily cointegrating the ZnO-Te AAS-based converter in the back-end-of-line structure.

Anti-Ambipolar Heterojunctions: Materials, Devices, and Circuits

Anti-ambipolar heterojunctions are vital in constructing high-frequency oscillators, fast switches, and multivalued logic (MVL) devices, which hold promising potential for next-generation integrated circuit chips and telecommunication technologies. Thanks to the strategic material design and device integration, anti-ambipolar heterojunctions have demonstrated unparalleled device and circuit performance that surpasses other semiconducting material systems. This review aims to provide a comprehensive summary of the achievements in the field of anti-ambipolar heterojunctions. First, the fundamental operating mechanisms of anti-ambipolar devices are discussed. After that, potential materials used in anti-ambipolar devices are discussed with particular attention to 2D-based, 1D-based, and organic-based heterojunctions. Next, the primary device applications employing anti-ambipolar heterojunctions, including anti-ambipolar transistors (AATs), photodetectors, frequency doublers, and synaptic devices, are summarized. Furthermore, alongside the advancements in individual devices, the practical integration of these devices at the circuit level, including topics such as MVL circuits, complex logic gates, and spiking neuron circuits, is also discussed. Lastly, the present key challenges and future research directions concerning anti-ambipolar heterojunctions and their applications are also emphasized.

A reconfigurable binary/ternary logic conversion-in-memory based on drain-aligned floating-gate heterojunction transistors

A new type of heterojunction non-volatile memory transistor (H-MTR) has been developed, in which the negative transconductance (NTC) characteristics can be controlled systematically by a drain-aligned floating gate. In the H-MTR, a reliable transition between N-shaped transfer curves with distinct NTC and monolithically current-increasing transfer curves without apparent NTC can be accomplished through programming operation. Based on the H-MTR, a binary/ternary reconfigurable logic inverter (R-inverter) has been successfully implemented, which showed an unprecedentedly high static noise margin of 85% for binary logic operation and 59% for ternary logic operation, as well as long-term stability and outstanding cycle endurance. Furthermore, a ternary/binary dynamic logic conversion-in-memory has been demonstrated using a serially-connected R-inverter chain. The ternary/binary dynamic logic conversion-in-memory could generate three different output logic sequences for the same input signal in three logic levels, which is a new logic computing method that has never been presented before.

Asymmetric two-dimensional ferroelectric transistor with anti-ambipolar transport characteristics

Two-dimensional (2D) ferroelectric transistors hold unique properties and positions, especially talking about low-power memories, in-memory computing, and multifunctional logic devices. To achieve better functions, appropriate design of new device structures and material combinations is necessary. We present an asymmetric 2D heterostructure integrating MoTe₂, h-BN, and CuInP₂S₆ as a ferroelectric transistor, which exhibits an unusual property of anti-ambipolar transport characteristic under both positive and negative drain biases. Our results demonstrate that the anti-ambipolar behavior can be modulated by external electric field, achieving a peak-to-valley ratio up to 10³. We also provide a comprehensive explanation for the occurrence and modulation of the anti-ambipolar peak based on a model describing linked lateral-and-vertical charge behaviors. Our findings provide insights for designing and constructing anti-ambipolar transistors and other 2D devices with significant potential for future applications.