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Achieving a low resistance contact is essential for developing two-dimensional (2D) material-based field-effect transistors (FETs). While n-type contacts to 2D semiconductors have been studied, understanding and designs for p-type contacts to 2D semiconductors remain very limited. In this study, we propose and computationally explore three strategies to improve the contact resistance in p-type 2D FETs, which remains a critical bottleneck of 2D logic technology, through the engineering of van der Waals (vdW) material heterostructures: (i) intercalating a graphene layer between a high-work-function metal and 2D semiconductor, which can result in low contact resistance of ~ 60 Ω μm for the graphene-intercalated contact between a high-work-function metal and WSe2 semiconductor; (ii) engineering the atomic stacking order between a vdW metal and 2D semiconductor, which can result in contact resistance of ~ 50 Ω μm; (iii) sandwiching the 2D layered semiconductor between vdW metals from both sides, which can further reduce the contact resistance to ~ 47 Ω μm and ~ 36 Ω μm for cases (i) and (ii), respectively. Experimental fabrication and characterization illustrate the feasibility of structural engineering of contacts. The above structural designs can lead to significantly reduced metal-induced gap states (MIGS) and low barrier height for holes, resulting in low contact resistance. They are also naturally compatible with the gate-all-around (GAA) transistor structure. In addition to contact materials selection, vdW structural design offers an alternative approach for achieving low contact resistance to p-type 2D FETs. [ABSTRACT FROM AUTHOR]

Image saliency detection is a process for highlighting the most salient object in an image and presenting the image saliency map. The content of an image is chaotic, including a complex background, low contrast, and an irregular salient object appearance. To overcome these problems, many algorithms have high computational complexity. In this paper, an efficient and fast-performing saliency detection algorithm is proposed, which consists of initiation saliency map generation and saliency map refinement. In the generation stage, the color-based contrast prior and color-based spatial distribution prior are effectively described in the image. Subsequently, two prior results (contrast value and distribution value) are fused to obtain an initial saliency map. In the refinement stage, the initial saliency map is refined by visual focus and an adaptive salient object mask (SOM). Due to the simplicity of the proposed algorithm, the system can detect salient objects in real time. Experimental evaluation on the benchmark shows that the proposed method can achieve sufficient accuracy and reliability while showing the lowest execution time. Compared with other methods, the execution time of the proposed method can achieve 137 frames per second (FPS) for the dataset with average image size 386 × 292. [ABSTRACT FROM AUTHOR]

We derive an alternative expression for a delayed logistic equation in which the rate of change in the population involves a growth rate that depends on the population density during an earlier time period. In our formulation, the delay in the growth term is consistent with the rate of instantaneous decline in the population given by the model. Our formulation is a modification of Arino et al. (J Theor Biol 241(1):109–119, 2006) by taking the intraspecific competition between the adults and juveniles into account. We provide a complete global analysis showing that no sustained oscillations are possible. A threshold giving the interface between extinction and survival is determined in terms of the parameters in the model. The theory of chain transitive sets and the comparison theorem for cooperative delay differential equations are used to determine the global dynamics of the model. We extend our delayed logistic equation to a system modeling the competition between two species. For the competition model, we provide results on local stability, bifurcation diagrams, and adaptive dynamics. Assuming that the species with shorter delay produces fewer offspring at a time than the species with longer delay, we show that there is a critical value, τ ∗ , such that the evolutionary trend is for the delay to approach τ ∗ . [ABSTRACT FROM AUTHOR]

In this article, the prolonged transient current and the coupled voltage retention behavior of ultrathin oxide MISTD induced by deep depletion of surrounded coupling electrode is investigated. The transient current is induced to balance the surrounded coupling electrode returning to its thermal equilibrium state, and the coupling voltage sensed is the result of the perturbation by the nearby deep depletion. The prolonged transient behavior of the sensed current is explained by the modulation of the hole leakage from the ring metal-insulator-semiconductor (MIS). Also, the behavior of the coupled voltage retention is the result of the generated electrons being swept toward the ring MIS by lateral field. The oxide thickness, coupling gap width, and trapping charges were shown to have influences on both behaviors. Moreover, the sensed coupled voltage of the center MISTD are utilized as memory characteristic and the operation of the proposed MIS memory cell is demonstrated. Oxide thickness smaller than 26 Å was proposed for the prolonged transient phenomenon. The power consumption of this device is very low due to limited saturation current. [ABSTRACT FROM AUTHOR]

We derive characteristic functions to determine the number and stability of relaxation oscillations for a class of planar systems. Applying our criterion, we give conditions under which the chemostat predator-prey system has a globally orbitally asymptotically stable limit cycle. Also we demonstrate that a prescribed number of relaxation oscillations can be constructed by varying the perturbation for an epidemic model studied by Li et al. [SIAM J. Appl. Math, 2016]. [ABSTRACT FROM AUTHOR]

In this study, we focus on lateral size effects of graphene nanosheets as conductive additives for LiNi0.5Co0.2Mn0.3O2 (NCM) cathode materials for Li-ion batteries. We used two different lateral sizes of graphene, 13 (GN-13) and 28 µm (GN-28). It can be found that the larger sheet sizes of graphene nanosheets give a poorer rate capability. The electrochemical measurements indicate that GN-13 delivers an average capacity of 189.8 mAh/g at 0.1 C and 114.2 mAh/g at 2 C and GN-28 exhibits an average capacity of 179.4 mAh/g at 0.1 C and only 6 mAh/g at 2 C. Moreover, according to the results of alternating current (AC) impedance, it can be found that the GN-28 sample has much higher resistance than that of GN-13. The reason might be attributed to that GN-28 has a longer diffusion distance of ion transfer and the mismatch of particle size between NCM and GN-28. The corresponding characterization might provide important reference for Li-ion battery applications. [ABSTRACT FROM AUTHOR]