Bi2O2Se is emerging as a photosensitive functional material for optoelectronics, and its photodetection mechanism is mostly considered to be a photoconductive regime in previous reports. Here, the bolometric effect is discovered in Bi2O2Se photodetectors. The coexistence of photoconductive effect and bolometric effect is generally observed in multiwavelength photoresponse measurements and then confirmed with microscale local heating experiments. The unique photoresponse of Bi2O2Se photodetectors may arise from a change of hot electrons during temperature rises instead of photoexcited holes and electrons. Direct proof of the bolometric effect is achieved by real‐time temperature tracking of Bi2O2Se photodetectors under time evolution after light excitation. Moreover, the Bi2O2Se bolometer shows a high temperature coefficient of resistance (−1.6% K−1), high bolometric coefficient (−31 nA K−1), and high bolometric responsivity (>320 A W−1). These findings offer a new approach to develop bolometric photodetectors based on Bi2O2Se layered materials.

Growing uniform oxides with various thickness on TMDs is one of the biggest challenges to integrate TMDs into complementary metal oxide semiconductor (CMOS) logic circuits. Here, we report a layer-by-layer oxidation of atomically thin MoTe flakes via ozone (O) exposure. The thickness of MoO oxide film could be tuning with atomic-level accuracy simply by varying O exposure time. Additionally, MoO -covered MoTe shows a hole-dominated transport behavior. Our findings point to a simple and effective strategy for growing homogeneous surface oxide film on MoTe, which is promising for several purposes in metal-oxide-semiconductor transistor, ranging from surface passivation to dielectric layers.

Controllably tuned infrared emissivity has attracted great interest for potential application in adaptive thermal camouflage. In this work, we report a flexible multilayer graphene based infrared device on a porous polyethylene membrane, where the infrared emissivity could be tuned by ionic liquid intercalation. The Fermi level of surface multilayer graphene shifts to a high energy level through ionic liquid intercalation, which blocks electronic transition below the Fermi level. Thus, the optical absorptivity/emissivity of graphene could be controlled by intercalation. Experimentally, the infrared emissivity of surface graphene was found to be tuned from 0.57 to 0.41 after ionic liquid intercalation. Meanwhile, the relative reflectivity Rv/R0 of surface graphene increased from 1.0 to 1.15. The strong fluorescence background of Raman spectra, the upshift of the G peak (~23 cm−1), and the decrease of sheet resistance confirmed the successful intercalation of ionic liquid into the graphene layers. This intercalation control of the infrared emissivity of graphene in this work displays a new way of building an effective thermal camouflage system.

2D materials with low-symmetry exhibit anisotropic physical properties, making them promising candidates for various applications. However, the lack of matured synthesis methods in anisotropic 2D materials is still the main obstacle to their future applications. Given the mature synthesis method of transition metal dichalcogenides (TMDCs), manipulating anisotropy in 2D TMDCs becomes a promising way to tune or trigger functional properties. Herein, for the first time, a van der Waals symmetry engineering is reported to introduce in-plane polarization in MoS 2 through contact with low-symmetric CrOCl. The emergence of asymmetric second harmonic generation pattern in MoS 2 /CrOCl heterojunction indicates the variation of lattice symmetry in MoS 2 . Furthermore, the theoretical simulation shows that such change stems from lattice-mismatch-induced uniaxial strain because of the strong interlayer interactions. The angle-dependent Raman and photoluminescence spectra further identify that the uniaxial strain gives rise to the in-plane polarization in MoS 2 . In addition, the polarized MoS 2 exhibits excellent orientation-sensitive electrical characteristics with a conductance anisotropy ratio of ≈1.5. More importantly, the strong linear polarization-sensitive photodetection is realized, and the anisotropic ratio reached 1.25 with 532 nm. The results suggest that symmetric engineering potentially opens up a new field to endow high-symmetry 2D materials with anisotropic functionalities.

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