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Despite monolayer transition metal dichalcogenide (TMD) shows a direct band gap property, its atomic thickness causes poor light absorption that severely limits its practical applications. For improving the optical gain of TMD, however, many approaches were proposed such as complicated fabrication process that compromises the stability and reliability of two-dimensional (2D) materials, which further limits the device scalability. In this work, a simple method is reported to engineer the light-matter interactions in few-layer molybdenum disulfide (MoS 2) and tungsten diselenide (WSe 2) via an asymmetric Fabry-Perot cavity (FPc). The cavity is based on the hybrid integration of TMD/hexagonal boron nitride (h-BN)/Au/SiO 2 heterostructure realized through layer-by-layer stacking. By modulating the underlying h-BN thickness, constructive resonant absorption can be achieved by multiple internal reflections, which significantly increases the Raman and optical absorption of MoS 2 and WSe 2. Leveraging on the enhanced light-matter interactions, we further integrate this asymmetric Fabry−Perot cavity into WSe 2 /MoS 2 van der Waals heterostructure (vdWH) to realize high performance photodiode and photovoltaic devices, leading to a ~5 folds increase in photodiode responsivity and a peak external quantum efficiency (EQE) of 7.5%. This work demonstrates an effective way towards hybrid integration of Fabry-Perot cavity with 2D materials, which could offer a potential pathway for enabling novel optoelectronic devices, such as 2D light-emitting diodes (LEDs) and solar cells. Image 1 • An asymmetric Fabry−Perot cavity composed of WSe 2 /MoS 2 /h-BN/Au/SiO 2 hybrid structure is realized by dry transfer technique. • Enhancement of Raman and absorption intensity are achieved from individual MoS 2 and WSe 2 by modulating the thickness of h-BN. • Integrating asymmetric Fabry−Perot cavity into WSe 2 /MoS 2 vdWH results in excellent photodiode and photovoltaic performance. [ABSTRACT FROM AUTHOR]

Abstract: This work investigates for the first time, the physics of carrier transport in a sub-90nm strained silicon-on-insulator (SOI) n-MOSFET with silicon–carbon (Si:C) source/drain (S/D) regions. The insertion of Si:C in the S/D exerts a lateral tensile strain in the transistor channel, leading to appreciable drive current enhancement. Significant improvement in both carrier backscattering r sat and source injection velocity υ inj were observed, accounting for the large drive current I Dsat enhancement in Si:C S/D transistors. This improvement becomes more appreciable as the gate length is reduced. The reduction in r sat is related to a shorter critical length ℓ0 for carrier backscattering. On the other hand, the splitting of six-fold degenerate conduction band valleys due to strain-induced effects results in a reduced in-plane transport mass and thus contributes to significant υ inj enhancement. In addition, the dependence of drive current performance on source injection velocity and ballistic efficiency in a short channel MOSFET is also discussed. [Copyright &y& Elsevier]

To accurately detect human motion, a sensing material/device must be flexible, ultrasensitive to strain, and electrically and mechanically robust. However, existing electronics and sensors, which are either not flexible enough, or not ultrasensitive to strain, or suffering from poor on/off ratio and low charge mobility, do not meet these stringent requirements. Here, we demonstrate a flexible and ultrasensitive three-terminal strain sensor based on two-dimensional (2D) InSe for detecting human-motion activities. The 2D InSe exhibits a tunable bandgap and a large piezoresistive effect via strain engineering. Through electrostatic gating effect, the gauge factor of the sensor can be enhanced by 8-fold and 7-fold for a low tensile and compressive strain of only ±0.25%, respectively. Remarkably, the fabricated 2D InSe-based transistor achieves both a record high on/off ratio of ~108 and an electron mobility of ~383 cm2/V s, superior to all existing ones. Furthermore, flexible InSe logic inverters with a high voltage gain of ~10 and a large noise margin of ~0.7 × V DD (supply voltage) are realized under various strain conditions. This work paves the way to enable simultaneous integration of high-performance flexible sensors and electronics based on a common 2D InSe material platform towards achieving a fully integrated sensing system. We report a flexible and ultrasensitive three-terminal strain sensor based on two-dimensional (2D) InSe material for human-motion detection, in which the strain sensor shows a prominent enhancement of sensitivity through gating effect. Simultaneously, InSe based flexible transistor and Boolean inverter circuit are demonstrated, which achieves a record high mobility of 383 cm2/V s and on/off current ratio of 108. This work manifests the potential of deploying InSe as a common material platform for next generation flexible electronics and strain sensors applications, paving the way towards achieving a fully integrated sensing system. Image 1 • 2D InSe with strong piezoresistivity and low Young's modulus manifests its potential for strain sensor application. • A three-terminal flexible InSe strain sensor with an ultrahigh sensitivity to human-motion detection is demonstrated. • High performance flexible InSe-based transistor with a record high on/off current ratio and carrier mobility is achieved. • InSe-based flexible inverter circuit with a high voltage gain and large noise margin is simultaneously demonstrated. • Our work paves the way towards the realization of a fully integrated sensing system based on a common InSe material platform. [ABSTRACT FROM AUTHOR]

• A novel carbon allotrope T 5 -carbon is predicted by using first-principles calculations. It has a Vickers hardness of 76.5 GPa, which is lower than that of diamond but larger than those of T-carbon and cubic boron nitride. The reason for the slight lower Vickers hardness of T 5 -carbon in comparison with diamond can be ascribed to the weaker bonding strengths in the carbon tetrahedron. A novel carbon allotrope is predicted by first-principles calculations. This allotrope is obtained by replacing one of the two atoms in the primitive cell of diamond with a carbon tetrahedron, thus it contains five atoms in one primitive cell, termed T 5 -carbon. The stabilities of T 5 -carbon are checked in structural, thermal and vibrational calculations. T 5 -carbon is a wide band gap semiconductor with an indirect band gap of 4.30 eV, and has a lattice thermal conductivity of 409 W/mK. Mechanical analyses reveal that T 5 -carbon shows good mechanical performances. Furthermore, by modifying T 5 -carbon with replacing some carbon atoms with Si or Ti atoms, we can obtain SiC 4 or TiC 4 structures. Importantly, the TiC 4 system has a moderate conduction and valance band edges, comparable larger absorption capacity of visible light and smaller effective masses of electron and hole carriers than TiO 2 , confirming its photocatalysis applications. [ABSTRACT FROM AUTHOR]