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Studies into scatterings of photonic structures have been so far overwhelmingly focused on their dependencies on the spatial and spectral morphologies of the incident waves. In contrast, evolutions of scattering properties through another parameter space of incident directions (momentum space) has not attracted sufficient attention, with the underlying general governing rules still unrevealed. Here, from the perspective of quasi‐normal modes (QNMs), the momentum‐space scattering extremizations with respect to varying incident directions of plane waves are investigated. It is revealed that for effective single‐QNM excitations, scatterings are maximized exactly along those directions where the QNM radiation reaches its maximum, with matched incident and radiation polarizations. For an arbitrary direction, when the incident polarization is tuned to be orthogonal to that of the mode radiation, the QNM cannot be excited and thus the scatterer becomes invisible with null scatterings. The principles revealed are protected by fundamental laws of reciprocity and energy conservation (optical theorem), which can be further expanded and applied for other branches of wave physics. [ABSTRACT FROM AUTHOR]

Abstract: Semiconducting molybdenum ditelluride (2H‐MoTe2), a fast‐emerging 2D material with an appropriate band gap and decent carrier mobility, is configured as field‐effect transistors and is the focus of substantial research interest, showing hole‐dominated ambipolar characteristics. Here, carrier modulation of ambipolar few‐layer MoTe2 transistors is demonstrated utilizing magnesium oxide (MgO) surface charge transfer doping. By carefully adjusting the thickness of MgO film and the number of MoTe2 layers, the carrier polarity of MoTe2 transistors from p‐type to n‐type can be reversely controlled. The electron mobility of MoTe2 is significantly enhanced from 0.1 to 20 cm2 V−1 s−1 after 37 nm MgO film doping, indicating a greatly improved electron transport. The effective carrier modulation enables to achieve high‐performance complementary inverters with high DC gain of >25 and photodetectors based on few‐layer MoTe2 flakes. The results present an important advance toward the realization of electronic and optoelectronic devices based on 2D transition‐metal dichalcogenide semiconductors. [ABSTRACT FROM AUTHOR]

Non-uniform photocurrent is usually generated at the overlapped region of the heterostructures, and its potential applications may be hindered by the spatial uniformity issue of the device photoresponse. Here, nearly a uniform photoresponse at the overlapped region of the thermally oxidized Ni and molybdenum disulphide (MoS2) heterostructures is obtained. Further characterizations reveal that several nanometers Ni is rightly under the NiOx layer formed at the surface of the film in the oxidation process. The heterostructures based on layered MoS2/NiOx/Ni with highly conductive bottom Ni show a high uniform photoresponse with an external quantum efficiency (EQE) of 1.4% at 532 nm. Moreover, successful integration of multiple devices suggests a great priority for such a structure for highly integrated uniform photodetectors. [ABSTRACT FROM AUTHOR]

2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light-matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few-layer rhenium disulfide (ReS2) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few-layer ReS2 flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications. [ABSTRACT FROM AUTHOR]