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The one-dimensional van der Waals (1D vdW) material fibrous red phosphorus (FRP) nanotubes are a promising direct-bandgap semiconductor with high carrier mobility and anisotropic optical responses because of low deformation potential and dangling-bond-free anisotropic interface. Employing first-principles calculations, we captured the potential of 1D FRP nanotubes. The thermal stability of 1D FRP nanotubes was confirmed by phonon calculation. Meanwhile, Raman spectroscopy indicated the strong vibration mode (366 cm

Molecular intercalation in black phosphorus shows tunable bandgap from 0.3 eV to 1.8 eV (covering from near-infrared to mid-infrared absorption spectra) with increase of intercalated molecule density (from 1 × 1020 cm−3 to 6.1 × 1020 cm−3).

Two-dimension (2D) ferroelectric field effect transistors (Fe-FETs) have attracted extensive interest as a competitive platform for implementing future-generation functional electronics, including digital memory and brain-inspired computing circuits. In 2D Fe-FETs,...

Two-dimensional (2D) transition-metal dichalcogenide materials (TMDs) alloys have a wide range of applications in the field of optoelectronics due to their capacity to achieve wide modulation of the band gap with fully tunable compositions. However, it is still a challenge for growing alloys with uniform components and large lateral size due to the random distribution of the crystal nucleus locations. Here, we applied a simple but effective promoter assisted liquid phase chemical vapor deposition (CVD) method, in which the quantity ratio of promoter to metal precursor can be controlled precisely, leading to tiny amounts of transition metal oxide precursors deposition onto the substrates in a highly uniform and reproducible manner, which can effectively control the uniform distribution of element components and nucleation sites. By this method, a series of monolayer Nb1−xWxSe2 alloy films with fully tunable compositions and centimeter scale have been successfully synthesized on sapphire substrates. This controllable approach opens a new way to produce large area and uniform 2D alloy film, which has the potential for the construction of optoelectronic devices with tailored spectral responses.

Over the past few decades, silicon-based solar cells have dominated the photovoltaic industry, and the interfacial morphology of crystalline silicon/amorphous silicon (c-Si/a-Si) is a key success factor to approach the theoretical efficiency of Si-based solar cells, especially Si heterojunction (SHJ) technology. One of the major issues plaguing the SHJ development, is the unexpected c-Si epitaxial growth and nanotwins formation at c-Si/a-Si interface. By a combination of atomic-resolution high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) images and in-situ high resolution transmission electron microscope (HRTEM), we obtained new finding in high-efficiency SHJ industrial devices, and simulated c-Si/a-Si interfacial morphology. Employing microsecond-long low-temperature (500 K) molecular dynamic simulations, we proposed a new strategy to prevent from both c-Si epitaxial growth and nanotwin formation, that the texture should have a decreased pyramid apex-angle (slightly smaller than 70.53°) in SHJ solar cells. The new apex-angle consists of hybrid (111)0.9/(011)0.1 c-Si planes, rather than pure (111) planes in conventional texture pyramid. The nature of the hybrid c-Si plane is low-energy c-Si/a-Si interface, which is unfavorable for either epitaxial c-Si growth or nanotwins formation. More importantly, given there is not any additional industrial preparation process, the new design of hybrid c-Si plane could improve c-Si/a-Si interfacial morphology for a-Si passivated contacts technique, and wide-applied for all silicon-based (single-junction and tandem) solar cells as well.

Single-layer graphene has been proved to be an ideal material for broadband high-speed photodetector. However, the pure graphene photodetector photoresponsivity is limited to tens of mA/W by the low optical absorption and short exciton life of graphene. When higher responsivity is needed, the graphene layer needs to be coupled with other materials, e.g., Titanium Dioxide (TiO2). Conventional TiO2 recipes require either solution or high temperature which tends to destruct the graphene layer. In this work, TiO2 is synthesized by oxygen plasma treating Ti film. This novel synthesis route of TiO2 avoids defects introduced by the conventional recipes. The hybrid device shows a high photoresponsivity of ~ 179 A/W, a fast response time of ~ 20 ms and a specific detectivity of ~ 9.12 × 109 Jones with the incident light intensity of sub-microwatt. Under the illumination, the photon absorption in graphene creates electron–hole pairs, which were separated at TiO2/graphene interface by an internal electric field and corresponding electrons transfer from the graphene to TiO2 layer. The high photoresponsivity is attributed to the long lifetime of the photoexcited charge carriers caused by a built-in field at the interface of TiO2/graphene. Our research provides an effective method to improve the photoresponse of the graphene-based photodetector. In addition, our TiO2 recipe could be applied in the fabrication of other electronic devices where solution or high temperature processes are difficult.

Two-dimensional (2D) materials have been demonstrated to be promising candidates to design high performance photodetectors owing to their strong light-matter interaction. However, the performance of 2D material photodetectors is still unsatisfactory, such as slow response speed due to defects and vulnerable contact interface, which impede their rapid development in the field of optoelectronics. In this paper, we obtained the ideal and large photosensitive van der Waals Schottky interface by the laminating-flipping method. Hence, a fast response speed ( 1012 Jones) are observed on the van der Waals Schottky junction photodiode. More importantly, benefiting from the flat Schottky interface (the roughness ∼0.6 nm), a sub-bandgap light response modulated by the Schottky barrier height (cut-off edge at 1050 nm) has been detected based on the large Au/MoSe2 sensitive Schottky interface internal photoemission. As a result, a universal strategy for the sub-bandgap near-infrared van der Waals Schottky junction detector of 2D materials was obtained.

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.

The emerging data-intensive applications in optoelectronics are driving innovation toward the fused integration of sensing, memory, and computing to break through the restrictions of the von Neumann architecture. However, the present photodetectors with only optoelectronic conversion functions cannot satisfy the growing demands of the multifunctions required in single devices. Here, a novel route for the integration of non-volatile memory into a photodetector is proposed, with a WSe

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.

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...

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.

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 MoS

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 (TMDs) are a category of promising two-dimensional (2D) materials for the optoelectronic devices, and their unique characteristics include tunable band gap, nondangling bonds as well as compatibility to large-scale fabrication, for instance, chemical vapor deposition (CVD). MoS

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.