Sodium‐Mediated Epitaxial Growth of 2D Ultrathin Sb₂Se₃ Flakes for Broadband Photodetection

Abstract

As an important member of group VA–VIA semiconductors, 2D Sb2Se3 has drawn widespread attention thanks to its outstanding optoelectronic properties as compared to the bulk material. However, due to the intrinsic chain‐like crystal structure, the controllable synthesis of ultrathin 2D planar Sb2Se3 nanostructures still remains a huge challenge. Herein, for the first time, the crystal structure limitation is overcome and the successful structural evolution of 2D ultrathin Sb2Se3 flakes (as thin as 1.3 nm), by introducing a sodium‐mediated chemical vapor deposition (CVD) growth method, is realized. The formation of 2D planar geometry is mainly attributed to the preferential growth of (010) plane with the lowest formation energy. The thickness‐dependent band structure of 2D Sb2Se3 flakes shows a wide absorption band from UV to NIR region (300–1000 nm), suggesting its potential application in broadband photodetection. Strikingly, the Sb2Se3 flakes–based photodetector demonstrates excellent performance such as broadband response varying from UV to NIR region, high responsivity of 4320 mA W−1, fast response time (τrise ≈ 13.16 ms and τdecay ≈ 9.61 ms), and strong anisotropic ratio of 2.5@ 532 nm, implying promising potential application in optoelectronics.

Low‐Symmetry and Nontoxic 2D SiP with Strong Polarization‐Sensitivity and Fast Photodetection

“…SHG microscopy is a useful tool to investigate nonlinear optical properties of 2D layered materials, which is very sensitive to lattice symmetry and sample thickness. [ 52,53 ] The SHG signals on 2D SiP flakes is performed to explore the nonlinear properties of 2D SiP via back‐reflection geometry, as shown in Figure a. Under the excitation source of 880 nm (9.1 mW), pronounced SHG signals are observed at 440 nm (Figure 4b) with the thickness of 2D SiP from 3.4 to 21.0 nm, indicating the asymmetric crystal structure of SiP.…”

“…For the ultrathin 2D crystal with the thickness smaller than the coherent length, the SHG is attributed to the strong absorption at 440 nm and efficient interference effect between fundamental and second harmonic (SH) wavelength. [ 52 ] For further investigations, we investigated wavelength dependence SHG spectra under various excitation wavelength, as shown in Figure 4c. The strongest SHG response is detected at 440 nm, which is due to the interference effect and the nonlinear coefficient dispersion as a function of the fundamental wavelength (Figure 4e).…”

Atomically Thin Hexagonal Boron Nitride and Its Heterostructures

“…Furthermore, the content of precursor in feedback is vital for the growth of 2D materials, [ 90–97 ] it can be also employed to tune the growth behaviors of h‐BN crystals. [ 80,82,98 ] This phenomenon is attributed to the modulated ratio of diffusion and availability of active N and B radicals, which makes crystal growth for either favorable triangular shape with N terminated edges or hexagonal shape with alternating N and B terminated edges.…”

Ultrasensitive Photodetectors Promoted by Interfacial Charge Transfer from Layered Perovskites to Chemical Vapor Deposition‐Grown MoS2

“…By assembly of van de Waals heterostructures [ 23,24 ] and interfacing these 2D materials with colloidal quantum dots, [ 9 ] metal‐halide perovskites [ 25 ] and organic molecules, [ 26 ] elevated light absorption, and introduction of gain mechanism have boosted the high responsivity of photodetectors, while the detectivity is still restricted. In addition, compared to their mechanical exfoliated counterparts, 2D materials grown by chemical vapor deposition (CVD), [ 27–29 ] which is significant for scalable integration of devices, exhibit inevitable high doping level and non‐radiative recombination losses due to their higher defect concentrations, [ 30,31 ] thus leading to high dark currents and limited photoresponse.…”