We present a van der Waals p-MoTe2/n-MoTe2 homojunction p–n diode with low resistance metal contacts.

Van der Waals heterostructures composed of transition-metal dichalcogenide (TMD) materials have become a remarkable compact system that could offer an innovative architecture for advanced engineering in high-performance energy-harvesting and optoelectronic devices. Here, we report a novel van der Waals (vdW) TMD heterojunction photodiode composed of black phosphorus (p-BP) and palladium diselenide (n-PdSe2), which establish a high and tunable rectification and photoresponsivity. A high rectification up to ≈7.1 × 105 is achieved, which is successfully tuned by employing the back-gate voltage to the heterostructure devices. Besides, the device significantly shows the high and gate-controlled photoresponsivity of R = 9.6 × 105, 4.53 × 105 and 1.63 × 105 A W–1 under the influence of light of different wavelengths (λ = 532, 1064, and 1310 nm) in visible and near-infrared regions, respectively, because of interlayer optical transition and low Schottky. The device also demonstrates extraordinary values of detectivity (D = 5.8 × 1013 Jones) and external quantum efficiency (EQE ≈ 9.4 × 106), which are an order of magnitude higher than the currently reported values. The effective enhancement of photovoltaic characteristics in visible and infrared regions of this TMD heterostructure-based system has a huge potential in the field of optoelectronics to realize high-performance infrared photodetectors.

2D layered germanium selenide (GeSe) with p-type conductivity is incorporated with asymmetric contact electrode of chromium/Gold (Cr/Au) and Palladium/Gold (Pd/Au) to design a self-biased, high speed and an efficient photodetector. The photoresponse under photovoltaic effect is investigated for the wavelengths of light (i.e. ~220, ~530 and ~850 nm). The device exhibited promising figures of merit required for efficient photodetection, specifically the Schottky barrier diode is highly sensitive to NIR light irradiation at zero voltage with good reproducibility, which is promising for the emergency application of fire detection and night vision. The high responsivity, detectivity, normalized photocurrent to dark current ratio (NPDR), noise equivalent power (NEP) and response time for illumination of light (~850 nm) are calculated to be 280 mA/W, 4.1 × 10 9 Jones, 3 × 10 7 W −1 , 9.1 × 10 −12 WHz −1/2 and 69 ms respectively. The obtained results suggested that p-GeSe is a novel candidate for SBD optoelectronics-based technologies. Two-dimensional (2D) materials have chronically been the most widely studied materials, particularly after the successful scotch tape test to exfoliate graphene by Andre Geim and Kostya Novoselov in 2004 1. 2D materials possess excellent electrical and mechanical properties toward diverse electronic device applications. Graphene, being the prototype of 2D materials 2,3 , has been studied broadly for its exotic electrical, optical, and mechanical properties 3,4. Besides, the group-IV transition metal dichalcogenides (TMDs) having a bandgap of around 1 to 2 eV 5-7 have attracted increasing interest because of their promising electronic and optoelectronic device applications 3,8-21. Graphene possesses extremely high carrier mobility (>10 5 cm 2 V −1 s −1), but the absence of band gap limits its electronic and optoelectronic applications 22. Therefore, TMDs with the properties of graphene-like stature, bandgap tunability, weak van der Waals-like forces and stability have intrigued the interest of the scientific community. TMDs are the family of 2D materials having the chemical composition of MX 2 , where M stands for the transition metal elements (M = Mo, W, Ta, Ge…etc) and X for the chalcogen elements (X = Se, S and Te). Among TMDs, Ge-based materials are preferred for applications due to their abundance on earth and environmentally friendly nature 23. With Se, the p-type Germanium from a narrow bandgap semiconductor material as p-GeSe having exciting application in near-infrared (NIR) photodetectors and electron tunnelling devices. p-GeSe has an indirect bandgap of 1.08 eV in the bulk 24,25 , and a direct bandgap of ~1.7 eV in monolayers 24,26,27. Few layers of p-GeSe can be obtained from bulk by mechanical exfoliation method 28. Among the many applications, p-GeSe shows tremendous capability in the realm of photovoltaics, because of its excellent optical, material and electrical properties. Therefore, it is well known as substitution of phosphorene 29. Moreover, GeSe is considered as an amb...

This paper reports on high photo responsivity (Rλ ∼ 1913 AW−1) of MoS2 photodetector by decorating a thin layer of ZnO quantum dots on MoS2.

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A few-layer WSe2/WS2 heterojunction diode on an h-BN substrate shows improved electronic and optoelectronic characteristics with a robust diode rectification ratio and photo responsivity compared to that on a SiO2 substrate.

One of the most prominent and effective applications of graphene in the field of spintronics is its use as a spacer layer between ferromagnetic metals in vertical spin valve devices, which are widely used as magnetic sensors. The magnetoresistance in such devices can be enhanced by a selection of suitable spacer materials and proper fabrication procedures. Here, we report the use of dry-transferred single- and double-layer graphene, grown by chemical vapor deposition (CVD), as the spacer layer and the fabrication procedure in which no photo-resist or electron-beam resists is used. The measured maximum magnetoresistance of NiFe/CVD-Graphene/Co junction is 0.9% for the single- and 1.2% for the double-layer graphene at 30 K. The spin polarization efficiency of the ferromagnetic electrodes is about 6.7% and 8% for the single- and the double-layer graphene, respectively, at the same temperature. The bias-independent magnetoresistance rules out any contamination and oxidation of the interfaces between the ferromagnet and the graphene. The magnetoresistance measured as a function of tilted magnetic field at different angles showed no changes in the maximum value, which implies that the magnetoresistance signal is absent from anisotropic effects.