Monolithic three-dimensional (M3D) integration represents a transformative approach in semiconductor technology, enabling the vertical integration of diverse functionalities within a single chip. This review explores the evolution of M3D integration from traditional bulk semiconductors to low-dimensional materials like two-dimensioanl (2D) transition metal dichalcogenides (TMDCs) and carbon nanotubes (CNTs). Key applications include logic circuits, static random access memory (SRAM), resistive random access memory (RRAM), sensors, optoelectronics, and artificial intelligence (AI) processing. M3D integration enhances device performance by reducing footprint, improving power efficiency, and alleviating the von Neumann bottleneck. The integration of 2D materials in M3D structures demonstrates significant advancements in terms of scalability, energy efficiency, and functional diversity. Challenges in manufacturing and scaling are discussed, along with prospects for future research directions. Overall, the M3D integration with low-dimensional materials presents a promising pathway for the development of next-generation electronic devices and systems.

Two-dimensional (2D) twisted moiré materials, a new class of van der Waals (vdW) layered heterostructures with different twist angles between neighboring layers, have attracted tremendous attention due to their rich emerging properties. In this review, we systematically summarize the recent progress of 2D twisted moiré materials. Firstly, we introduce several representative fabrication methods and the fascinating topographies of the twisted moiré materials. Specifically, we discuss various remarkable physical properties related to twisted angles, including flat bands, unconventional superconductivity, ferromagnetism, and ferroelectricity. We also analyze the potential applications in various twisted moiré systems. Finally, the challenges and future perspectives of the twisted moiré materials are discussed. This work would spur edge-cutting ideas and related achievements in the scientific and technological frontiers of 2D twisted moiré materials.

Transition metal dichalcogenides (TMD) heterostructure is widely applied for second harmonic generation (SHG) and holds great promises for laser source, nonlinear switch, and optical logic gate. However, for atomically thin TMD heterostructures, low SHG conversion efficiency would occur due to reduction of light–matter interaction length and lack of phase matching. Herein, we demonstrated a facile directional SHG amplifier formed by MoS₂/WS₂ monolayer heterostructures suspended on a holey SiO₂/Si substrate. The SHG enhancement factor reaches more than two orders of magnitude in a wide spectral range from 355 to 470 nm, and the radiation angle is reduced from 38° to 19° indicating higher coherence and better emission directionality. The giant SHG enhancement and directional emission are attributed to the great excitation and emission field concentration induced by a self-formed vertical Fabry–Pérot microcavity. Our discovery gives helpful insights for the development of two-dimensional (2D) nonlinear optical devices.