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Emerging freestanding membrane technologies, especially using inorganic thermoelectric materials, demonstrate the potential for advanced thermoelectric platforms. However, using rare and toxic elements during material processing must be circumvented. Herein, we present a scalable method for synthesizing highly crystalline CuS membranes for thermoelectric applications. By sulfurizing crystalline Cu, we produce a highly percolated and easily transferable network of submicron CuS rods. The CuS membrane effectively separates thermal and electrical properties to achieve a power factor of 0.50 mW m−1 K−2 and thermal conductivity of 0.37 W m−1 K−1 at 650 K (estimated value). This yields a record‐high dimensionless figure‐of‐merit of 0.91 at 650 K (estimated value) for covellite. Moreover, integrating 12 CuS devices into a module resulted in a power generation of ~4 μW at ΔT of 40 K despite using a straightforward configuration with only p‐type CuS. Furthermore, based on the temperature‐dependent electrical characteristics of CuS, we develop a wearable temperature sensor with antibacterial properties. [ABSTRACT FROM AUTHOR]

The pursuit of sub‐1‐nm field‐effect transistor (FET) channels within 3D semiconducting crystals faces challenges due to diminished gate electrostatics and increased charge carrier scattering. 2D semiconductors, exemplified by transition metal dichalcogenides, provide a promising alternative. However, the non‐idealities, such as excess low‐frequency noise (LFN) in 2D FETs, present substantial hurdles to their realization and commercialization. In this study, ideal LFN characteristics in monolayer MoS2 FETs are attained by engineering the metal‐2D semiconductor contact and the subgap density of states (DOS). By probing non‐ideal contact resistance effects using CuS and Au electrodes, it is uncovered that excess contact noise in the high drain current (ID) region can be substantially reduced by forming a van der Waals junction with CuS electrodes. Furthermore, thermal annealing effectively mitigates sulfur vacancy‐induced subgap density of states (DOS), diminishing excess noise in the low ID region. Through meticulous optimization of metal‐2D semiconductor contacts and subgap DOS, alignment of 1/f noise with the pure carrier number fluctuation model is achieved, ultimately achieving the sought‐after ideal LFN behavior in monolayer MoS2 FETs. This study underscores the necessity of refining excess noise, heralding improved performance and reliability of 2D electronic devices. [ABSTRACT FROM AUTHOR]

This work features a thin, flexible thermoelectric membrane in a multifunctional wearable device, highlighting its advanced energy harvesting capabilities. [ABSTRACT FROM AUTHOR]

Two–dimensional materials have the potential to be applied in flexible and transparent electronics. In this study, single-layer MoS2 field-effect transistors (FETs) with Au/Ti–graphene heteroelectrodes were fabricated to examine the effect of the electrodes on the electrical properties of the MoS2 FETs. The contact barrier potential was tuned using an electric field. Asymmetrical gate behavior was observed owing to the difference between the MoS2 FETs, specifically between the MoS2 FETs with Au/Ti electrodes and those with graphene electrodes. The contact barrier of the MoS2 FETs with Au/Ti electrodes did not change with the electric field. However, the contact barrier at the MoS2–graphene interface could be modulated. The MoS2 FETs with Au/Ti–graphene electrodes exhibited enhanced on/off ratios (~102 times) and electron mobility (~2.5 times) compared to the MoS2 FETs with Au/Ti electrodes. These results could improve the understanding of desirable contact formation for high-performance MoS2 FETs and provide a facile route for viable electronic applications. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures based on two-dimensional (2D) transition metal dichalcogenides (TMDCs), particularly WS2/MoS2 heterostructures with type-II band alignments, are considered as ideal candidates for future functional optoelectronic applications owing to their efficient exciton dissociation and fast charge transfers. These physical properties of vdW heterostructures are mainly influenced by the interlayer coupling occurring at the interface. However, a comprehensive understanding of the interlayer coupling in vdW heterostructures is still lacking. Here, we present a detailed analysis of the low-frequency (LF) Raman modes, which are sensitive to interlayer coupling, in bilayers of MoS2, WS2, and WS2/MoS2 heterostructures directly grown using chemical vapor deposition to avoid undesirable interfacial contamination and stacking mismatch effects between the monolayers. We clearly observe two distinguishable LF Raman modes, the interlayer in-plane shear and out-of-plane layer-breathing modes, which are dependent on the twisting angles and interface quality between the monolayers, in all the 2D bilayered structures, including the vdW heterostructure. In contrast, LF modes are not observed in the MoS2 and WS2 monolayers. These results indicate that our directly grown 2D bilayered TMDCs with a favorable stacking configuration and high-quality interface can induce strong interlayer couplings, leading to LF Raman modes. [ABSTRACT FROM AUTHOR]