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Two-dimensional (2D) materials and their derived quasi one-dimensional structure provide incredible possibilities for the field of photoelectric detection due to their intrinsic optical and electrical properties. However, the photogenerated carriers in atomically thin media are poor due to the low optical absorption, which greatly limits their performance. Here, in the MoS2 nanoscroll photodetector, we meticulously investigated the avalanche multiplication effect. The results show that by employing the nanoscroll structure, the required threshold electrical field for triggering avalanche multiplication is significantly lower than that of MoS2 flake due to the modulation of the energy band and intervalley scattering through the strain effect. Consequently, avalanche multiplication could efficiently enhance the photoresponsivity to >104 A/W. Furthermore, enhanced avalanche multiplication could be generalized to other TMDCs through theoretical prediction. The results not only are significant for the understanding of the intrinsic nature of 2D materials but also reveal meaningful advances in high-performance and low-power consumption photodetection.

Graphene has some outstanding properties in the photoelectric field, especially ultra fast response and broad spectrum absorption, which have led to strong attraction on graphene photodetector. However, the photoresponsivity of pure graphene device is below 10 mA W−1. It would limit the application of graphene photodetector. Here, we design a metamaterial structure with a broadband high absorption spectrum. And by integrating it into the graphene photodetector, the high photoresponsivity of a pure graphene photodetector in a broadband range could be acquired. The photoresponsivity of photodetector can achieve nearly 200 mA W−1, which is two orders higher than the one of pure monolayer graphene photodetector. Besides, the photodetector also keeps the broadband photoresponse. The hot carriers can be generated by coupling of multiple resonances and effectively transported to graphene with the advantage of ultrathin metal film. Based on this work, more potential applications of graphene photodetector could be developed in some related fields.

Strain engineering is proposed to be an effective technology to tune the properties of two-dimensional (2D) transition metal dichalcogenides (TMDCs). Conventional strain engineering techniques (e.g., mechanical bending, heating) cannot conserve strain due to their dependence on external action, which thereby limits the application in electronics. In addition, the theoretically predicted strain-induced tuning of electrical performance of TMDCs has not been experimentally proved yet. Here, a facile but effective approach is proposed to retain and tune the biaxial tensile strain in monolayer MoS2 by adjusting the process of the chemical vapor deposition (CVD). To prove the feasibility of this method, the strain formation model of CVD grown MoS2 is proposed which is supported by the calculated strain dependence of band gap via the density functional theory (DFT). Next, the electrical properties tuning of strained monolayer MoS2 is demonstrated in experiment, where the carrier mobility of MoS2 was increased by two orders (∼ 0.15 to ∼ 23 cm2·V−1·s−1). The proposed pathway of strain preservation and regulation will open up the optics application of strain engineering and the fabrication of high performance electronic devices in 2D materials.

Transition metal dichalcogenides (TMDs) are a category of promising two-dimensional (2D) materials for the optoelectronic devices, and their unique characteristics include tunable band gap, nondang...

Photodetectors based on two-dimensional materials have shown impressive performance including fast and broadband photoresponse and high responsivity. However, their polarization sensitivity remains to be improved. Here, we propose an antimonene photodetector having a strong polarization sensitivity with a broadband photoresponse, based on quantum transport calculations. A robust photocurrent is generated for almost the whole visible range under small bias, and it saturates at a small bias voltage for most of the photon energies. The photocurrent shows a perfect cosine dependence on the polarization angle, which originates from a second-order response to the electric field of the light. This leads to a strong polarization sensitivity to the linearly polarized light with a large extinction ratio. For a higher photon energy around 3.2 eV, a rather high extinction ratio greater than 100 can be achieved along with a larger photocurrent. Moreover, there is an evident anisotropy between the armchair and zigzag directions, as the photocurrent intensity in the zigzag direction can be approximately 17 times larger than that in the armchair direction at a small bias. These results suggest that antimonene is a promising candidate for anisotropic photodetection in the visible range especially for high frequency visible light.

Transition metal dichalcogenides (TMDCs) are promising for future electronic and optoelectronic applications, such as field effect transistors (FETs), for their high carrier mobility with a thin layer, wide bandgap, and organic-like flexibility. However, background doping and unipolar electrical characteristics are commonly observed in TMDCs and their based FETs due to the naturally inevitable vacancy defects, which limit their application in electronics and optoelectronics systems. Here, taking MoS2 as an example, in a TMDC FET, ambipolar properties were achieved at room temperature by introducing an amorphous solid ionic conductor lithium tantalate (LiTaO3) as the gate dielectric, which could guarantee the modulation of the Fermi level in the MoS2 channel by the gate electric field. Based on the modulation mechanisms by the solid ionic conductor-gated electric field for the transformation of conduction mode, the three-terminal device exhibits a gate-controlled rectifying, that is, thyristor performance with a high rectification ratio over 300 obtained at a low gate voltage of 2 V. The present results show the great potential of TMDCs in future logic and other electronic device applications.