which is located in the near-infrared and visible region. [9] Bandgaps in TMDCs are tunable by applying external electric field or mechanical strain. Combined with broad-band optical absorption and mechanical flexibility, TMDCs are one of appealing materials for the application in optoelectronic devices such as field effect transistors, photodetectors, and light-emitting diodes. Photodetectors based on molybdenum disulfide (MoS 2 ), [1,3] tungsten disulfide (WS 2 ), [10,11] molybdenum diselenide (MoSe 2 ), [7,8] and their heterojunctions [12] were constructed and exhibited photoresponsivity ranging from a few mA W −1 to several hundred A W −1 , which is related to the materials selected, layer numbers, and device contacts. Intrinsically, the photoresponsivity is restricted by their absorption cross section and present lower values because of small thickness of TMDCs. [9] Integration of TMDC materials into photonic structures such as photonic crystals and microcavities offers a solution to enhance the photoresponsivity. [13][14][15] For example, Fano-resonant photonic crystals could significantly boost light absorption in monolayer MoS 2 and the absorption can reach up to 90% at the resonant wavelength. [13] Another typical approach to enhancing photoresponsivity is to hybridize TMDCs with plasmonic structures. A MoS 2 photodetector hybridized with Ag nanowire network was demonstrated and presented greatly enhanced photocurrent over the pristine MoS 2 photodetectors because of surface plasmon coupling. [5] However, the photoresponsivity can be only enhanced at designed and selected wavelength in these hybrid photodetectors mentioned above. It is promising that 3D mesostructures could enhance light absorption over wide range due to its circular geometry and thus improve photoelectric performance. [16][17][18][19] Rolled-up inorganic nanomembrane-based 3D architectures, [20][21][22] such as nanoscrolls and nanosprings, have great potential in applications of supercapacitors, [23] optical microcavity, [24][25][26] actuators, [27,28] resistive random access memory, [29] motors, [30] etc., because of their distinct properties arising from 3D geometry. In this work, a 3D tubular photodetector is proposed to increase the photoresponsivity of 2D materials benefiting from the significantly enhanced light absorption. We introduce this tubular microstructure into the MoSe 2based photodetector for improved detection performance. 3D photodetector based on rolled-up MoSe 2 nanomembrane was Transition metal dichalcogenides, as a kind of 2D material, are suitable for near-infrared to visible photodetection owing to the bandgaps ranging from 1.0 to 2.0 eV. However, limited light absorption restricts photoresponsivity due to the ultrathin thickness of 2D materials. 3D tubular structures offer a solution to solve the problem because of the light trapping effect which can enhance optical absorption. In this work, thanks to mechanical flexibility of 2D materials, self-rolled-up technology is applied to build up a 3D tubular structure ...

Nanoscale-layered ferromagnets have demonstrated fascinating two-dimensional magnetism down to atomic layers, providing a peculiar playground of spin orders for investigating fundamental physics and spintronic applications. However, the strategy for growing films with designed magnetic properties is not well established yet. Herein, we present a versatile method to control the Curie temperature (T C ) and magnetic anisotropy during the growth of ultrathin Cr 2 Te 3 films. We demonstrate an increase of the T C from 165 to 310 K in sync with magnetic anisotropy switching from an out-of-plane orientation to an in-plane one, respectively, via controlling the Te source flux during film growth, leading to different c-lattice parameters while preserving the stoichiometries and thicknesses of the films. We attributed this modulation of magnetic anisotropy to the switching of the orbital magnetic moment, using X-ray magnetic circular dichroism analysis. We also inferred that different c-lattice constants might be responsible for the magnetic anisotropy change, supported by theoretical calculations. These findings emphasize the potential of ultrathin Cr 2 Te 3 films as candidates for developing room-temperature spintronics applications, and similar growth strategies could be applicable to fabricate other nanoscale layered magnetic compounds.

This study examined the structural, chemical, and electrical properties of solution-processed (Zn,Sn)O3 (ZTO) films with various Sn/[Zn+Sn] ratios for potential applications to large-area flat panel displays. ZTO films with a Zn-rich composition had a polycrystalline wurtzite structure. On the other hand, the Sn-rich ZTO films exhibited a rutile structure, where the Zn atom was speculated to replace the Sn site, thereby acting as an acceptor. In the intermediate composition regions (Sn/[Zn+Sn] ratio from 0.28 to 0.48), the ZTO films had an amorphous structure, even after annealing at 450 °C. The electrical transport properties and photobias stability of ZTO thin film transistors (TFTs) were also examined according to the Sn/[Zn+Sn] ratio. The optimal transport property of ZTO TFT was observed for the device with an amorphous structure at a Sn/[Zn+Sn] ratio of 0.48. The mobility, threshold voltage, subthreshold swing, and on/off current ratio were 4.3 cm(2)/(V s), 0 V, 0.4 V/decade, and 4.1 × 10(7), respectively. In contrast, the device performance for the ZTO TFTs with either a higher or lower Sn concentration suffered from low mobility and a high off-state current, respectively. The photoelectrical stress measurements showed that the photobias stability of the ZTO TFTs was improved substantially when the ZTO semiconducting films had a lower oxygen vacancy concentration and an amorphous structure. The relevant rationale is discussed based on the phototransition and subsequent migration mechanism from neutral to positively charged oxygen vacancies.

The transition-metal dichalcogenide VSe2 exhibits an increased charge density wave transition temperature and an emerging insulating phase when thinned to a single layer. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these phases in single-layer VSe2 using ultrafast pump–probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap, which we disentangle from the ensuing hot carrier dynamics by fitting a model spectral function to the time-dependent photoemission intensity. This procedure leads to an estimated time scale of 480 fs for the closure of the gap, which suggests that the phase transition in single-layer VSe2 is driven by electron–lattice interactions rather than by Mott-like electronic effects. The ultrafast optical switching of these interactions in SL VSe2 demonstrates the potential for controlling phase transitions in 2D materials with light.

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