Two-dimensional heterostructures and their device applications: progress, challenges and opportunities—review

Abstract

This work presents a review on the current progress, challenges, and potential future development opportunities for two-dimensional material-based heterostructures, including their fabrication techniques as well as their applications in various functional devices. The fabrication techniques for two-dimensional material-based vertical heterostructure are first reviewed and discussed, including artificial stacking, chemical vapor deposition, molecular beam epitaxy, and others. Then, twodimensional material-based lateral heterostructure growth techniques are reviewed, including chemical vapor deposition and others. Subsequently, various functional device applications based on twodimensional material-based heterostructures are systematically reviewed and discussed, including electronic devices, optoelectronic devices, electrochemical devices, and others. The advantages and disadvantages for each fabrication/growth technique are compared and analyzed, including those for both vertical and lateral heterostructures. In addition, the current primary challenges for further development of two-dimensional material-based heterostructures and their functional devices are discussed and analyzed, including lack of precise control, low interface/surface quality, surface passivation issue, low light absorption, lack of system integration and application, complex device fabrication process, as well as low device fabrication efficiency. Various potential solutions are proposed that have the potential to overcome these existing primary challenges to achieve better device performance and thus their ultimate industry applications for the two-dimensional material-based heterostructures.

SnSe Nanoplates for Photodetectors with a High Signal/Noise Ratio

“…Some atoms nucleate and grow on energetically preferential sites, while other unrecombined atoms are desorbed and carried away by the bulk gas flow. As discussed in ref , two types of fluxes exist in the reaction, in terms of the active molecules/atoms that coexist on the surface: a flux of SnSe molecules transported to the substrate surface by the carrier gas, F transport , and another flux associated with the molecule reacting rate on the substrate surface, F reaction . These two fluxes are in series, and the slower one restricts the growth of SnSe nanoplates.…”

“…Moreover, the EQE for this SnSe nanoplate photodetector is 408.37% under the 400 nm laser illumination with an intensity of 38.3 mW cm –2 . This large EQE (>1) here is mainly due to the photoconductive gain: the majority carriers (electrons) have a short transit time across the device in comparison to the minority carrier (holes) leading to a high photocurrent in the outside circuit per incident photon Figure c,d presents the response time of the photoresponse signal of the SnSe nanoplate photodetector.…”

“…This large EQE (>1) here is mainly due to the photoconductive gain: the majority carriers (electrons) have a short transit time across the device in comparison to the minority carrier (holes) leading to a high photocurrent in the outside circuit per incident photon. 12 Figure 8c,d presents the response time of the photoresponse signal of the SnSe nanoplate photodetector. The rising time (t rising ) and reset time (t reset ) are measured to be 0.24 and 0.15 s, respectively.…”

“…In the past few decades, low-dimensional semiconductors have received extensive attention, including quantum wells, quantum dots, quantum wires, nanowires, nanobelts, and nanoplates . Because of their favorite physical properties, such as high carrier mobility along with quantum wells, they can be used for fabricating high-performance microelectronic and optoelectronic devices, such as high-speed transistors, low-threshold current lasers, high-sensitivity detectors, etc. − Over the years, the research on low-dimensional semiconductors and devices has made significant progress. Various types of high-quality low-dimensional materials and devices have been reported, such as InAs quantum dots, InAsSb quantum wires, InAs nanowires, and Bi 2 Te 3 nanoplates. ,,, In the meantime, as essential functional materials, metal chalcogenides are studied for optical, electronic, and optoelectronic device applications due to their rich physical and chemical properties. − Combining metal chalcogenides with low-dimensional structures will leverage the advantages of the two and lead to new physical characteristics and functional devices with better performance, which presents an interesting research area to be well explored.…”

Recent Research Progress in the Structure, Fabrication, and Application of MXene-Based Heterostructures

“…Vertical MXene-based heterostructures are synthesized by stacking independent monolayer 2D materials layer-by-layer through direct growth or the mechanical transfer method, which provides the heterostructure with a strong intralayer covalent bond and relatively weak interlayer vdW interaction, generating a system not limited by the lattice matching degree of the materials [ 57 , 58 ]. Due to the absence of suspended bonds and the weak vdW forces between the layered structures, the vertical MXene-based heterostructure can be easily constructed by stacking different materials.…”