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Register a new userHigh responsivity phototransistors based on few-layer ReS2 for weak signal detection
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Two-dimensional 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 and weak signal detection are required. Here, we present high responsivity phototransistors based on few-layer rhenium disulfide (ReS2). 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 two-dimensional 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.
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We present prominent photoresponse of bio-inspired graphene-based phototransistors sensitized with chlorophyll molecules. The hybrid graphene-chlorophyll phototransistors exhibit a high gain of 10^6 electrons per photon and a high responsivity of 10^6 A/W, which can be attributed to the integration of high-mobility graphene and the photosensitive chlorophyll molecules. The charge transfer at interface and the photogating effect in the chlorophyll layer can account for the observed photoresponse of the hybrid devices, which is confirmed by the back-gate-tunable photocurrent as well as the thickness and time dependent studies of the photoresponse. The demonstration of the graphene-chlorophyll phototransistors with high gain envisions a viable method to employ biomaterials for graphene-based optoelectronics.
Atomically-thin two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have been extensively studied in recent years because of their appealing electrical and optical properties. Here, we report on the fabrication of ReS2 field-effect transistors via the encapsulation of ReS2 nanosheets in a high-k{appa} Al2O3 dielectric environment. Low-temperature transport measurements allowed us to observe a direct metal-to-insulator transition originating from strong electron-electron interactions. Remarkably, the photodetectors based on ReS2 exhibit gate-tunable photoresponsivity up to 16.14 A/W and external quantum efficiency reaching 3,168 %, showing a competitive device performance to those reported in graphene, MoSe2, GaS and GaSe-based photodetectors. Our study unambiguously distinguishes ReS2 as a new candidate for future applications in electronics and optoelectronics.
We report electron transport studies in an encapsulated few-layer WTe$_2$ at low temperatures and high magnetic fields. The magnetoconductance reveals a temperature-induced crossover between weak antilocalization (WAL) and weak localization (WL) in quantum diffusive regime. We show that the crossover clearly manifests coexistence and competition among several characteristic lengths, including the dephasing length, the spin-flip length, and the mean free path. In addition, low temperature conductance increases logarithmically with the increase of temperature indicating an interplay of electron-electron interaction (EEI) and spin-orbit coupling (SOC). We demonstrate the existences and quantify the strengths of EEI and SOC which are considered to be responsible for gap opening in the quantum spin hall state in WTe2 at the monolayer limit.
Semiconducting two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as top candidates for post-silicon electronics. While most of 2D TMDs exhibit isotropic behavior, lowering the lattice symmetry could induce anisotropic properties, which are both scientifically interesting and potentially useful. Here, we present atomically thin rhenium disulfide (ReS2) flakes with a unique distorted 1T structure, which exhibit in-plane anisotropic properties. We fabricated mono- and few-layer ReS2 field effect transistors (FETs), which exhibit competitive performance with large current on/off ratios (~107) and low subthreshold swings (100 mV dec-1). The observed anisotropic ratio along two principle axes reaches 3.1, which is the highest among all known 2D semiconducting materials. Furthermore, we successfully demonstrated an integrated digital inverter with good performance by utilizing two ReS2 anisotropic FETs, suggesting the promising implementation of large-scale 2D logic circuits. Our results underscore the unique properties of 2D semiconducting materials with low crystal symmetry for future electronic applications.
We demonstrate that surface relaxation, which is insignificant in trilayer graphene, starts to manifest in Bernal-stacked tetralayer graphene. Bernal-stacked few-layer graphene has been investigated by analyzing its Landau level spectra through quantum capacitance measurements. We find that in trilayer graphene, the interlayer interaction parameters were similar to that of graphite. However, in tetralayer graphene, the hopping parameters between the bulk and surface bilayers are quite different. This shows a direct evidence for the surface relaxation phenomena. In spite of the fact that the Van der Waals interaction between the carbon layers is thought to be insignificant, we suggest that the interlayer interaction is an important factor in explaining the observed results and the symmetry-breaking effects in graphene sublattice are not negligible.
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