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The fabrication of van der Waals heterostructures (vdWHs) has drawn considerable interest because of their wide range of functionalities. Herein, a novel PdSe2/ReSe2 vdWHs with gate‐tunable rectification behavior and excellent broadband photodetection characteristics is presented. The application of the gate bias substantially enhances the rectification behavior, with the highest rectification ratio (≈3.13 × 103) observed at gate voltage Vg = −60 V. The density functional theory calculations demonstrate the direct and indirect bandgap behavior of PdSe2 and ReSe2 in the monolayer structure, respectively. Additionally, the PdSe2/ReSe2 heterojunction displays a strong photo‐response in the near‐infrared region and achieves a high photoresponsivity, an excellent external quantum efficiency, and rapid rise and decay times of 1.7 × 103 A W−1, 4.05 × 103, and 5 and 20 ms, respectively. Furthermore, the device exhibits a remarkable detectivity of ≈3.5 × 1012 Jones. The findings hold great potential for advancing the fabrication of multifunctional vdW heterostructure devices. [ABSTRACT FROM AUTHOR]

Visible near infrared (VNIR) transition‐metal dichalcogenides (TMDs) photodetectors have attracted attention due to their unique electronic and optoelectronic properties. Herein, the photodetection performance of a novel MoTe2/ReSe2 van der Waals heterojunction (vdW HJ) diode is studied in the VNIR region. Density functional theory calculations reveal the formation of type‐II band alignment, which is beneficial for the design of a MoTe2/ReSe2 HJ diode with better optoelectronic properties. A superb rectification ratio of ≈1 × 104 is obtained via gate engineering, in which the ambipolar nature of MoTe2 enables a transition from p+–i to n–n+ state. In addition, the diode exhibits an excellent figure of merit for photodetection. The excellent diode performance is demonstrated by a high responsivity of 5.6 × 102 A W−1, an excellent detectivity of 8.1 × 1013 jones, and an external quantum efficiency of 9.5 × 102. Moreover, fast rise and decay times of 2 and 4 ms, respectively, are observed under illumination. The significant improvement is attributed to the combination of an intra‐TMD band‐to‐band transition and an inter‐TMD charge transfer process in the MoTe2/ReSe2 vdW HJ. This study provides an opportunity for advancing the prospects of TMDs in next generation optoelectronics. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) heterostructure with atomically sharp interface holds promise for future electronics and optoelectronics because of their multi-functionalities. Here we demonstrate gate-tunable rectifying behavior and self-powered photovoltaic characteristics of novel p-GeSe/n-MoSe2 van der waal heterojunction (vdW HJ). A substantial increase in rectification behavior was observed when the devices were subjected to gate bias. The highest rectification of ~ 1 × 104 was obtained at Vg = − 40 V. Remarkable rectification behavior of the p-n diode is solely attributed to the sharp interface between metal and GeSe/MoSe2. The device exhibits a high photoresponse towards NIR (850 nm). A high photoresponsivity of 465 mAW−1, an excellent EQE of 670%, a fast rise time of 180 ms, and a decay time of 360 ms were obtained. Furthermore, the diode exhibits detectivity (D) of 7.3 × 109 Jones, the normalized photocurrent to the dark current ratio (NPDR) of 1.9 × 1010 W−1, and the noise equivalent power (NEP) of 1.22 × 10–13 WHz−1/2. The strong light-matter interaction stipulates that the GeSe/MoSe2 diode may open new realms in multi-functional electronics and optoelectronics applications. [ABSTRACT FROM AUTHOR]

In this paper, the oxidation and wetting behaviour of Sn-0.7Cu and Sn-0.7Cu-0.05Fe-2Bi solder alloys has been investigated. The alloys were subjected to 200 °C in oxygen rich environment. Weight gain curves reveal that the oxidation behaviour obey the parabolic rate law. X-Ray photo electron spectroscopy (XPS) reveals the presence of SnO and SnO 2 oxide layer on the surface of Sn-0.7Cu solder alloys. SnO was formed as the basic oxide layer. However, at higher temperature SnO transforms into SnO 2. Addition of Bi results in the formation of Bi 2 O 3. The Pilling-Bedworth ratio of SnO, SnO 2 and Bi 2 O 3 oxides are 1.28, 1.35 and 1.23 respectively. These ratios confirm the passive nature of oxide layers. Wetting behaviour of Sn-0.7Cu and Sn-0.7Cu-0.05Fe-2Bi were investigated on Cu substrate. The addition of Bi and Fe improves the wetting properties of Sn-0.7Cu solder alloys. Alloying with Bi and Fe results in growth suppression of intermetallic compound at the interface. Increase in spreading rate, decrease in wetting angle and solder height reveals better performance of the Sn-0.7Cu-0.05Fe-2Bi solder alloy. [Display omitted] • Addition of Bi decreases the oxidation resistance of Sn-0.7Cu solder alloy. • In Bi added alloy, the thickness of oxide layer increases due to formation of Bi 2 O 3. • XPS analysis revealed Bi 2 O 3 as the outermost oxide layer, followed by SnO 2 and SnO. • Incorporation of Fe and Bi improves the wetting properties of Sn-0.7Cu alloy. • Growth suppression of IMC was observed with the addition of Bi and Fe. [ABSTRACT FROM AUTHOR]

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 × 109 Jones, 3 × 107 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. [ABSTRACT FROM AUTHOR]

Van der Waals (vdW) heterostructures composed of atomically thin two‐dimensional (2D) materials have more potential than conventional metal‐oxide semiconductors because of their tunable bandgaps, and sensitivities. The remarkable features of these amazing vdW heterostructures are leading to multi‐functional logic devices, atomically thin photodetectors, and negative differential resistance (NDR) Esaki diodes. Here, an atomically thin vdW stacking composed of p‐type black arsenic (b‐As) and n‐type tin disulfide (n‐SnS2) to build a type‐III (broken gap) heterojunction is introduced, leading to a negative differential resistance device. Charge transport through the NDR device is investigated under electrostatic gating to achieve a high peak‐to‐valley current ratio (PVCR), which improved from 2.8 to 4.6 when the temperature is lowered from 300 to 100 K. At various applied‐biasing voltages, all conceivable tunneling mechanisms that regulate charge transport are elucidated. Furthermore, the real‐time response of the NDR device is investigated at various streptavidin concentrations down to 1 pm, operating at a low biasing voltage. Such applications of NDR devices may lead to the development of cutting‐edge electrical devices operating at low power that may be employed as biosensors to detect a variety of target DNA (e.g., ct‐DNA) and protein (e.g., the spike protein associated with COVID‐19). [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenide semiconductors owning a large intrinsic spin-orbit coupling (SOC) are considered the best candidates to generate, detect and manipulate the spin currents. The SOC defines the interconversion of spin and charge currents via Rashba Edelstein effect (spin Hall effect) and its reciprocal as inverse Rashba Edelstein effect (inverse spin Hall effect). However, the spin signal originated in low dimensional materials because of Rashba Edelstein effect or spin Hall effect yet needed to be addressed with distinguishable measurement technique. Here, we demonstrate experimentally the room temperature interconversion of spin and charge currents in Graphene/WSe 2 van der Waals heterostructure which is induced by proximity effect. Remarkably, the spin currents induced by Rashba Edelstein effect and spin Hall effect are discriminated and extracted individually via external magnetic field, respectively. The magnitude of spin transport and their corresponding spin efficiencies ( α RE E = 1.47 ± 0.03 %) and (θ SHE = = 4.5 ± 0.07 %) are modulated via applied electric field and temperature. Such electric, and magnetic field tunability of the spin transport through the non-magnetic materials may provide a new approach to fabricate the fast and low-power spintronic devices for quantum scale applications. • Experimental demonstration of interconversion of spin and charge currents in Graphene/WSe 2 van der Waals heterostructure, induced by proximity of WSe 2 , at room temperature. • Remarkably, the spin currents induced by Rashba Edelstein effect and spin Hall effect are discriminated and their corresponding spin efficiencies are extracted individually via external magnetic field, respectively. [ABSTRACT FROM AUTHOR]

In recent times, 2D materials-based heterostructures are extensively studied for fabricating different nanodevices. Among these materials, transition metal dichalcogenides (TMDC), hexagonal boron nitride (hBN), and graphene (Gr) are widely used in these devices. Optoelectronic memory devices based on 2D materials are among the recently studied devices for structural flexibility and device size miniaturization. In this study, a non-volatile optoelectronic memory device has been fabricated using tungsten diselenide (WSe 2), and hBN-encapsulated Gr-based heterostructures. This device can be easily controlled with UV light and an electric field. Two points were focused on in this study; first, the doping state was changed partially i.e., by illuminating a part of the WSe 2 layer by UV light and a p-n homo-junction was created. This phenomenon occurs due to the unique structure of Wse 2 /hBN and the p-n junction could be created in one layer. Secondly, Gr has been used as a floating gate to increase the retention time as Gr is acting as a charge trapping layer. The retention time is further increased due to the thickness of hBN because the defect states keep increasing the charges together. [Display omitted] • Fabrication of an optoelectronic memory device using WSe 2 , and hBN encapsulated Gr-based heterostructures • Memory device can be easily controlled with UV light and an electric field. • Graphene used as a floating gate to increase the retention time as Gr is acting as a charge trapping layer. • The retention time improvement with the thickness of hBN because the defect states keep increasing the charges together. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the electronic, optical, and thermoelectric properties of two newly designed pyrochlore oxides, La 2 Q 2 O 7 (Q ​= ​Ge, Sn), based on first-principles calculations in the framework of DFT. The energy band gap shifts from direct to indirect band gap as Sn cation is replaced with Ge cation. The energy band gaps are 1.12 and 2.60 ​eV for La 2 Ge 2 O 7 and La 2 Sn 2 O 7 , respectively. The TDOS spectra clearly indicate that there is no magnetic moment in the studied compounds. The ε 2 (ω) spectra reveal that these materials absorb maximum photons in the visible and lower UV regions. La 2 Q 2 O 7 (Q ​= ​Ge, Sn) are efficient optical materials as their n (ω) value is between 1.0 and 2.0. The R (ω) spectra show up to 50% photon reflection in the UV region; however, the reflectance is negligible in the IR and visible regions. The Seebeck coefficient spectra reveal that these pyrochlore oxides are p-type semiconductors over the entire temperature range. La 2 Q 2 O 7 (Q ​= ​Ge, Sn) are efficient thermoelectric materials as their figure of merit (ZT) is approximately 1. [Display omitted] • Effect of Ge and Sn replacement on the optoelectronic and thermoelectric properties of La 2 Q 2 O 7 (Q ​= ​Ge, Sn). • First-principles calculations were used to calculate their electronic, optical and thermoelectric properties. • The exchange and correlation potential (EXC) was treated by the GGA approximation with addition of Hubbard correction (GGA+U). • Optical spectra show the main absorption peaks in the visible and ultraviolet (UV) region. • Both materials show good values of Seebeck coefficient (S) and are potential candidates for thermoelectric application. [ABSTRACT FROM AUTHOR]

• Assembled the Perovskite heterojunction device using different electron transport layers. • RF sputtering was used to deposit IGZO, SnO 2 , and IGZO/SnO 2 on PCBM as ETL. • A high solar cell efficiency of 12.56% was achieved for IGZO/SnO 2 mixed PCBM ETL. • Invented photodetector with IGZO/SnO 2 /PCBM exposed a sensitivity of 3.98 mA/Gy cm2. [Display omitted] We developed heterojunction electron-transfer layers (ETLs) comprising layers of metal oxides and phenyl-C 71 -butyric acid methyl ester (PCBM) for use in glass/indium tin oxide/hole transport layer/Perovskite/ETL/LiF/Al solar cells and X-ray detectors. Indium gallium zinc oxide (IGZO), tin oxide (SnO 2), or IGZO/SnO 2 layers were stacked on a PCBM layer via radio frequency (RF) magnetron sputtering at various temperatures. The formation of the metal-oxide layers and on a PCBM film were confirmed by conducting compositional and elemental mapping studies. Current-voltage experimental results show that the heterojunction fabricated by forming a IGZO/SnO 2 layer on a PCBM film possessed higher charge carrier capacity and exciton dissociation properties compared with using either IGZO or SnO 2 separately. The Perovskite solar cell with an IGZO/SnO 2 @100/PCBM (100 refers 100oC of RF sputtering temperature) ETL attained a power conversion efficiency (PCE) of 12.56 ± 0.15%, which was 36% more efficient than a device with a pure PCBM ETL (PCE = 9.22 ± 0.09%). Moreover, an X-ray detector fabricated with an IGZO/SnO 2 @100/PCBM ETL obtained a maximum sensitivity of 3.98 mA/Gy·cm2 and collected charge density (CCD)-dark current density (DCD) of 13.29 μA/cm2. [ABSTRACT FROM AUTHOR]

Two-terminal, non-volatile memory devices are the fundamental building blocks of memory-storage devices to store the required information, but their lack of flexibility limits their potential for biological applications. After the discovery of two-dimensional (2D) materials, flexible memory devices are easy to build, because of their flexible nature. Here, we report on our flexible resistive-switching devices, composed of a bilayer tin-oxide/tungsten-ditelluride (SnO2/WTe2) heterostructure sandwiched between Ag (top) and Au (bottom) metal electrodes over a flexible PET substrate. The Ag/SnO2/WTe2/Au flexible devices exhibited highly stable resistive switching along with an excellent retention time. Triggering the device from a high-resistance state (HRS) to a low-resistance state (LRS) is attributed to Ag filament formation because of its diffusion. The conductive filament begins its development from the anode to the cathode, contrary to the formal electrochemical metallization theory. The bilayer structure of SnO2/WTe2 improved the endurance of the devices and reduced the switching voltage by up to 0.2 V compared to the single SnO2 stacked devices. These flexible and low-power-consumption features may lead to the construction of a wearable memory device for data-storage purposes. [ABSTRACT FROM AUTHOR]

• Simple chemical reduction employed to form the Mo 2 C and Mo 2 C-CNTs nanostructures. • For the first time, Mo 2 C-CNTs blended PEDOT:PSS comprised devices were constructed. • Mo 2 C-CNTs@PEDOT:PSS layer comprised PSC produced an enhanced efficiency of ~11.98%. • High sensitivity of 3.56 mA/Gy·cm2 sensed for Mo 2 C-CNT@HTL involved X-ray detector. Transition metal carbide (Mo 2 C) and carbon nanotubes (CNTs) have been used to modify the hole transport layers (HTLs) in perovskite solar cells (PSCs) and photodetectors due to their high metallic conductivity, superior charge extraction probability, tunable work function, and high reliability. Here, for the first time, Mo 2 C, CNTs, and a Mo 2 C-CNT hybrid were blended with a PEDOT:PSS HTL in an ITO/HTL/CH 3 NH 3 PbI 3 /PCBM/LiF/Al device architecture. The power conversion efficiency of the resulting PSC improved to 11.98% with the use of Mo 2 C-CNT@PEDOT:PSS HTL compared to the pure PEDOT:PSS (9.17%), Mo 2 C@PEDOT:PSS (9.82%) and CNT@PEDOT:PSS (10.61%) HTLs. The PSC performance of device prototypes with different loadings (1, 1.5, and 2 wt%) of the Mo 2 C@CNT nanocomposite in the HTL was also examined. The prepared Mo 2 C-CNT@PEDOT:PSS HTL-based device was then employed as X-ray photodetector, achieving a maximum sensitivity of 3.56 mA/Gy·cm2. Our findings illustrate the potential for the use of MXene-CNT nanocomposites with a perovskite layer to enhance the efficacy of solar cells and photodetectors. [ABSTRACT FROM AUTHOR]

The electronic properties of single-layer, CVD-grown graphene were modulated by deep ultraviolet (DUV) light irradiation in different radiation environments. The graphene field-effect transistors (GFETs), exposed to DUV in air and pure O2, exhibited p-type doping behavior, whereas those exposed in vacuum and pure N2 gas showed n-type doping. The degree of doping increased with DUV exposure time. However, n-type doping by DUV in vacuum reached saturation after 60 min of DUV irradiation. The p-type doping by DUV in air was observed to be quite stable over a long period in a laboratory environment and at higher temperatures, with little change in charge carrier mobility. The p-doping in pure O2 showed ~15% de-doping over 4 months. The n-type doping in pure N2 exhibited a high doping effect but was highly unstable over time in a laboratory environment, with very marked de-doping towards a pristine condition. A lateral pn-junction of graphene was successfully implemented by controlling the radiation environment of the DUV. First, graphene was doped to n-type by DUV in vacuum. Then the n-type graphene was converted to p-type by exposure again to DUV in air. The n-type region of the pn-junction was protected from DUV by a thick double-coated PMMA layer. The photocurrent response as a function of Vg was investigated to study possible applications in optoelectronics. [ABSTRACT FROM AUTHOR]

Herein, the fabrication of a novel highly sensitive and fast hydrogen (H2) gas sensor, based on the Ta2O5 Schottky diode, is described. First, Ta2O5 thin films are deposited on silicon carbide (SiC) and silicon (Si) substrates via a radio frequency (RF) sputtering method. Then, Pd and Ni are respectively deposited on the front and back of the device. The deposited Pd serves as a H2 catalyst, while the Ni functions as an Ohmic contact. The devices are then tested under various concentrations of H2 gas at operating temperatures of 300, 500, and 700 °C. The results indicate that the Pd/Ta2O5 Schottky diode on the SiC substrate exhibits larger concentration and temperature sensitivities than those of the device based on the Si substrate. In addition, the optimum operating temperature of the Pd/Ta2O5 Schottky diode for use in H2 sensing is shown to be about 300 °C. At this optimum temperature, the dynamic responses of the sensors towards various concentrations of H2 gas are then examined under a constant bias current of 1 mA. The results indicate a fast rise time of 7.1 s, and a decay of 18 s, for the sensor based on the SiC substrate. [ABSTRACT FROM AUTHOR]