Sachin R. Suryawanshi

Vapor-liquid-solid growth of one-dimensional tin sulfide (SnS) nanostructures with promising field emission behavior.

Single-crystalline ultralong tin sulfide (SnS) nanowires has been grown by a thermal evaporation technique under optimized conditions on gold-coated silicon substrates, and for the first time, field emission investigations on the SnS nanowires at the base pressure of 1 × 10(-8) mbar are reported. It has been revealed that the surface morphology of the as-synthesized SnS nanostructures is significantly influenced by the deposition temperature and duration. Structural and morphological analyses of as-synthesized SnS nanostructures have been carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). To understand the optical and electronic properties of as-synthesized SnS nanowires, ultraviolet-visible (UV-vis), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) studies were carried out. The SEM and TEM measurements reveal the formation of ultralong SnS nanowires, with an average diameter of 80 nm. A plausible explanation on the vapor-solid-liquid (VLS) growth mechanism based on the experimental results and reported literature has been presented. Furthermore, the field emission characteristics of the SnS nanowires are found to be superior to the other metal chalcogenide nanostructures. The synthesized SnS nanowire emitter delivers a high current density of ∼2.5 mA/cm(2) at an applied electric field of ∼4.55 V/μm. The emission current stability over a period of 6 h is observed to be good. The observed results demonstrate the potential of the SnS nanowire emitter as an electron source for practical applications in vacuum nano/microelectronic devices.

Facile synthesis of Ag nanowire–rGO composites and their promising field emission performance

Crystalline, ultra long silver nanowires (Ag NWs), few-layered rGO (reduced graphene oxide) and their rGO–Ag NW nanocomposite have been synthesized using a polyol reflux technique under optimized experimental conditions. The field emission performance of the rGO–Ag NW nanocomposite, rGO and Ag NW emitters was investigated. The turn on field required to draw an emission current density of ∼1 μA cm−2 was found to be ∼5.00, 3.92 and 2.40 V μm−1 for the Ag NW, rGO and rGO–Ag NW nanocomposite emitters, respectively. The combined contribution of the sharp edges of the thin graphene sheets and high aspect ratio of the Ag nanowires, and their synergetic effect in the rGO–Ag NW nanocomposite, are responsible for the enhanced field emission behavior. First-principles density functional calculations show that the enhanced field emission may also be due to the overlapping of the electronic structures of the Ag NWs and rGO nanosheets.

3D Hetero-architecture of GdB6 nanoparticles on lessened cubic Cu2O nanowires: enhanced field emission behaviour

The field emission properties (FE) of a heteroarchitecture comprised of gadolinium hexaboride nanoparticles uniformly decorated over Cu2O nanoneedles (GdB6/Cu2O) have been investigated at the base pressure of ~1 × 10−8 mbar. Under the optimized pulsed laser deposition (PLD), a well-adhered coating of GdB6 nanoparticles on chemically synthesized cuprous oxide (Cu2O) nanoneedles has been obtained. A plausible growth mechanism of the hierarchical assembly of GdB6 nanoparticles on the Cu2O nanoneedles is explained on the basis of structural analysis carried out using SEM and TEM. A low turn-on field of ~2.3 V μm−1 (to draw an emission current density ~1 μA cm−2) is observed along with stable emission current at the preset value of ~2 μA over 4 h. The enhanced emission behaviour of the GdB6/Cu2O heteroarchitecture, in contrast to the pristine Cu2O nanoneedles, is attributed to its high aspect ratio and low work function. The observed FE results demonstrate GdB6/Cu2O heteroarchitecture as a potential candidate for application in various vacuum nano/microelectronic devices.

Enhanced field emission behavior of layered MoSe2

Herein, we report one step facile chemical vapor deposition method for synthesis of single-layer MoSe2 nanosheets with average lateral dimension ~60 μm on 300 nm SiO2/Si and n-type silicon substrates and field emission investigation of MoSe2/Si at the base pressure of ~1 × 10−8 mbar. The morphological and structural analyses of the as-deposited single-layer MoSe2 nanosheets were carried out using an optical microscopy, Raman spectroscopy and atomic force microscopy. Furthermore, the values of turn-on and threshold fields required to extract an emission current densities of 1 and 10 μA cm−2, are found to be ~1.9 and ~2.3 V μm−1, respectively. Interestingly, the MoSe2 nanosheet emitter delivers maximum field emission current density of ~1.5 mA cm−2 at a relatively lower applied electric field of ~3.9 V μm−1. The long term operational current stability recorded at the preset values of 35 μA over 3 hr duration and is found to be very good. The observed results demonstrates that the layered MoSe2 nanosheet based field emitter can open up many opportunities for their potential application as an electron source in flat panel display, transmission electron microscope, and x-ray generation. Thus, the facile one step synthesis approach and robust nature of single-layer MoSe2 nanosheets emitter can provide prospects for the future development of practical electron sources.

Vapour–liquid–solid growth of one-dimensional In2Se3 nanostructures and their promising field emission behaviour

Single crystalline ultra long In2Se3 nanowires have been grown by employing a single step facile thermal evaporation route under optimized conditions on Au/Si wafers, and morphology dependent field emission investigations on the In2Se3 nanostructure at the base pressure ∼1 × 10−8 mbar are explored. In addition, structural and morphological analysis of as-synthesized In2Se3 nanostructures has been carried out using XRD, SEM and TEM. A plausible explanation of the vapor–solid–liquid (VLS) growth mechanism based on the experimental results and reported literature has been presented. Furthermore, field emission measurements demonstrate remarkably enhanced emission behaviour, which is explained on the basis of the field enhancement factor and aspect ratio of the nanostructures. The synthesized In2Se3 nanowire emitter delivers a very high current density of ∼1.2 mA cm−2 at an applied electric field of ∼6.33 V μm−1. The present results demonstrate In2Se3 as an important candidate for potential applications in nano/micro-electronic devices.

Pt-nanoparticle functionalized carbon nano-onions for ultra-high energy supercapacitors and enhanced field emission behaviour

In the present work, we have investigated the charge storage capacitive response and field emission behaviour of platinum (Pt) nanoparticles decorated on carbon nano onions (CNOs) and compared them with those of pristine carbon nano onions. The specific capacitance observed for Pt–CNOs is 342.5 F g−1, about six times higher than that of pristine CNOs, at a scan rate of 100 mV s−1. The decoration with Pt nanoparticles, without any binder or polymer separator on the CNO, leading to enhanced supercapacitance is due to easy accessibility of Na2SO4 electrolyte in the active material. The Density Functional Theory (DFT) calculations of these systems reveal enhancement in the Density of States (DOS) near the Fermi energy (EF) on account of platinum decoration on the CNOs. Furthermore, the field emission current density of ∼0.63 mA cm−2 has been achieved from the Pt-CNOs emitter at an applied electric field of ∼4.5 V μm−1 and from the pristine CNOs sample current density of ∼0.4 mA cm−2 has been achieved at an applied electric field of ∼6.6 V μm−1. The observed enhanced field emission behavior has been attributed to the improved electrical conductivity and increased emitting sites of the Pt–CNO emitter. The field emission current stability of the Pt–CNO emitter over a longer duration is found to be good. The observed results imply multifunctional potential of Pt–CNOs, as supercapacitor material in various next generation hybrid energy storage devices, and field emitters for next generation vacuum nano/microelectronic devices.

Laser exfoliation of 2D black phosphorus nanosheets and their application as a field emitter

Highly crystalline two dimensional (2D) few layered black phosphorus (BP) nanosheets have been synthesized via a one step facile laser irradiation technique under optimized experimental conditions. The field emission investigations on the few layered black phosphorus nanosheets were carried out at the base pressure 1 × 10−8 mbar. The morphological, elemental, optical, and structural analysis of the as-synthesized black phosphorus sample was carried out using SEM, AFM, EDAX, TEM, and Raman spectroscopy. The turn-on values of the BP nanosheets emitter were found to be significantly lower than that of earlier reports of BP nanosheets, graphene, and carbon nanotubes based field emitters due to the high field enhancement factor (β) ∼2986 associated with atomically thin/sharp edges of the BP nanosheets emitter. The emission current versus time plot depicts the good emission current stability with a pre-set value of 1 μA for ∼5 h duration. Our facile synthesis approach and the robust field emitter nature of the BP nanosheets makes them a potential candidate for a practical electron source in vacuum micro/nanoelectronic devices.

Exfoliated 2D black phosphorus nanosheets: Field emission studies

A few layer black phosphorus (BP) nanosheets are obtained by micromechanical cleavage from a bulk BP crystal. In a typical exfoliation procedure, a layer of BP is peeled off from bulk crystal with the help of Scotch tape and transferred onto SiO2/Si and pristine Si substrates. The morphological and structural analyses of the samples were carried out using an optical microscopy, a transmission electron microscopy, and a Raman spectroscopy. Field emission investigations on a few layered BP nanosheets on Si substrate were carried out at the base pressure of 1 × 10−8 mbar. The turn-on value, corresponding to emission current density of ∼1 μA/cm2, is found to be ∼5.1 V/μm for BP nanosheets/Si emitter and high field enhancement factor (β) ∼1164, attributed to atomically thin/sharp edges of the BP nanosheets. The emission current shows good stability at a preset value of ∼5 μA over a period of more than 8 h. The present results demonstrate the potential of the mechanically exfoliated BP nanosheets/Si field emitt...

Low frequency noise and photo-enhanced field emission from ultrathin PbBi2Se4 nanosheets

Atomically thin two-dimensional layered materials have gained wide interest owing to their novel properties and potential for applications in nanoelectronic and optoelectronic devices. Here, we present the spectral analysis and photo-enhanced field emission studies of a layered intergrowth PbBi2Se4 nanosheet emitter, performed at the base pressure of ∼1 × 10−8 mbar. The emitter shows a turn-on field value of ∼4.80 V μm−1, corresponding to an emission current density of ∼1 μA cm−2. Interestingly, when the cathode was illuminated with visible light, it exhibited a lower turn-on field of ∼3.90 V μm−1, and a maximum emission current density of ∼893 μA cm−2 has been drawn at an applied electric field of ∼8.40 V μm−1. Furthermore, the photo-enhanced emission current showed reproducible, step-like switching behavior in synchronous with ON–OFF switching of the illumination source. The emission current–time plots reveal excellent stability over a duration of ∼6 h. Low-frequency noise is a significant limitation for the performance of nanoscale electronic devices. The spectral analysis performed on a Fast Fourier Transform (FFT) analyzer revealed that the observed noise is of 1/fα type, with the value of α ∼0.99. The low frequency noise, photo-enhanced field emission, and reproducible switching behavior characterized with very fast rise and fall times propose the layered PbBi2Se4 nanosheet emitter as a new promising candidate for novel vacuum nano-optoelectronic devices.

High-field emission performance of a NiFe2O4/rGO/CNT tertiary nanocomposite

Herein, we report the field emission properties of NiFe2O4/reduced graphene oxide/carbon nanotubes (NGC) and compared them with the field emission properties of NiFe2O4/carbon nanotubes (NC) and NiFe2O4/reduced graphene oxide (NG). The NGC nanocomposite showed a very low turn-on field of ∼0.4 V μm−1 and a high emission current density of ∼8.228 mA cm−2 at a low applied electric field of 1.6 V μm−1. In addition, it exhibited extremely good emission current stability at a preset value of ∼20 μA. The observed very low turn on field of the NGC nanocomposite is due to its lower value of effective work function (1.92 eV), and the results suggest the potential of the synthesized emitter for practical applications in vacuum micro-electronics/nano-electronics.