Reliable fabrication of micro/nanostructures with sub-10 nm features is of great significance for advancing nanoscience and nanotechnology. While the capability of current complementary metal-oxide semiconductor (CMOS) chip manufacturing can produce structures on the sub-10 nm scale, many emerging applications, such as nano-optics, biosensing, and quantum devices, also require ultrasmall features down to single digital nanometers. In these emerging applications, CMOS-based manufacturing methods are currently not feasible or appropriate due to the considerations of usage cost, material compatibility, and exotic features. Therefore, several specific methods have been developed in the past decades for different applications. In this review, we attempt to give a systematic summary on sub-10 nm fabrication methods and their related applications. In the first and second parts, we give a brief introduction of the background of this research topic and explain why sub-10 nm fabrication is interesting from both scientific and technological perspectives. In the third part, we comprehensively summarize the fabrication methods and classify them into three main approaches, including lithographic, mechanics-enabled, and post-trimming processes. The fourth part discusses the applications of these processes in quantum devices, nano-optics, and high-performance sensing. Finally, a perspective is given to discuss the challenges and opportunities associated with this research topic.

The 2D/1D mixed‐dimensional van der Waals heterostructures have great potential for electronics and optoelectronics with high performance and multifunctionality. The epitaxy of 1D micro/nanowires on 2D layered materials may efficiently realize the large‐scale preparation of 2D/1D heterostructures, which is critically important for their practical applications. So far, however, only the wires of Bi2S3, Te, and Sb2Se3 have been epitaxially grown on MoS2 or WS2. Here, it is reported that the epitaxial growth of 1D CsPbBr3 nanowires on 2D Bi2O2Se nanoplates through a facile vertical vapor deposition method. The CsPbBr3 wires are well aligned on the Bi2O2Se plates in fourfold symmetry with the epitaxial relationships of [001]CsPbBr3||[200]Bi2O2Se and [1‐10]CsPbBr3||[020]Bi2O2Se. The photoluminescence results reveal that the emission from CsPbBr3 is significantly quenched in the heterostructure, which implies the charge carriers transfer from CsPbBr3 to Bi2O2Se. The waveguide characterization shows that the epitaxial CsPbBr3 wires may efficiently confine and guide their emission, which favors the light absorption of Bi2O2Se. Importantly, the photocurrent mapping and spectra of the devices based on these 2D/1D heterostructures prove that the epitaxial CsPbBr3 wires remarkably enhances the photoresponse of Bi2O2Se, which indicates these heterostructures can be applied in high‐performance optoelectronic devices or on‐chip integrated photonic circuits.

Cesium copper (I) halides, as a lead-free halide material system, have shown great potential in optoelectronic devices due to their environmental friendliness, high quantum efficiency, and extraordinary air stability. However, most of the previous reports are on quantum dots, bulk crystals, or freestanding wires. It is still challenging to realize the in-plane growth of one-dimensional (1D) cesium copper (I) halides on various substrates, which is essential for nanodevices with high integration density. Herein, we report the planar growth of CsCu 2 I 3 nanoribbons (NBs) with high-quality single crystals on diverse substrates through a spatial-confined method. The in situ investigation of the growth process reveals that the morphology evolution of the NBs is controlled by both thermodynamics and kinetics that are dependent on the local supersaturation near the NBs. The CsCu 2 I 3 NB-based photodetectors (PDs) exhibit an outstanding ultraviolet (UV) detection performance with a high responsivity (0.27 A/W), a specific detectivity (6.38 × 10 8 Jones), and a fast photoresponse speed (t rise /t decay = 5.8/6.0 ms). Furthermore, the PDs exhibit high stability to light illumination and excellent flexibility to bending. The direct in-plane growth of the lead-free CsCu 2 I 3 NBs on various substrates would promote the practical application of copper (I) halides in electronics and optoelectronics.

Planar heterostructures composed of two or more adjacent structures with different materials are a kind of building blocks for various applications in surface plasmon resonance sensors, rectifiers, photovoltaic devices, and ambipolar devices, but their reliable fabrication with controllable shape, size, and positioning accuracy remains challenging. In this work, we propose a concept for fabricating planar heterostructures via directional stripping and controlled nanofractures of metallic films, with which self-aligned, multimaterial, multiscale heterostructures with arbitrary geometries and sub-20 nm gaps can be obtained. By using a split ring as the template, the asymmetric nanofracture of the deposited film at the split position results in nonreciprocal peeling of the film in the split ring. Compared to the conventional processes, the final heterostructures are defined only by their outlines, thus providing the ability to fabricate complex heterostructures with higher resolutions. We demonstrate that this method can be used to fabricate heterodimers, multimaterial oligomers, and multiscale asymmetrical electrodes. An Ag−MoS 2 −Au photodiode with a strong rectification effect is fabricated based on the nanogap heterostructures prepared by this method. This technology provides a unique and reliable approach to define nanogap heterostructures, which are supposed to have potential applications in nanoelectronics, nanoplasmonics, nanooptoelectronics, and electrochemistry.

Ultrasmall metallic nanogaps are of great significance for wide applications in various nanodevices. However, it is challenging to fabricate ultrasmall metallic nanogaps by using common lithographic methods due to the limited resolution. In this work, we establish an effective approach for successful formation of ultrasmall metallic nanogaps based on the spontaneous nanoscale dewetting effect during metal deposition. By varying the initial opening size of the exposed resist template, the influence of dewetting behavior could be adjusted and tiny metallic nanogaps can be obtained. We demonstrate that this method is effective to fabricate diverse sub-10 nm gaps in silver nanostructures. Based on this fabrication concept, even sub-5 nm metallic gaps were obtained. SERS measurements were performed to show the molecular detection capability of the fabricated Ag nanogaps. This approach is a promising candidate for sub-10 nm metallic gaps fabrication, thus possessing potential applications in nanoelectronics, nanoplasmonics, and nano-optoelectronics.