Flexible Field Emission Devices Research Articles

High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays

In this paper, a facile method to fabricate the flexible field emission devices (FEDs) based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED) and energy dispersive X-ray spectrometer (EDX), while the morphology was revealed by field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the SiC nanowires grew along the [111] direction with the diameter of ∼110 nm and length of∼30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (∼0.95 V/μm) and threshold field (∼3.26 V/μm), and the high field enhancement factor (β=4670). It is worth noting the current density degradation can be controlled lower than 2% per hour during the stability tests. In addition, the flexible FEDs based on SiC nanowire emitters exhibit uniform bright emission modes under bending test conditions. As a result, this strategy is very useful for its potential application in the commercial flexible FEDs.

Carbon and metal nanotube hybrid structures on graphene as efficient electron field emitters

We report a facile and efficient method for the fabrication of highly-flexible field emission devices by forming tubular hybrid structures based on carbon nanotubes (CNTs) and nickel nanotubes (Ni NTs) on graphene-based flexible substrates. By employing an infiltration process in anodic alumina oxide (AAO) templates followed by Ni electrodeposition, we could fabricate CNT-wrapped Ni NT/graphene hybrid structures. During the electrodeposition process, the CNTs served as Ni nucleation sites, resulting in a large-area array of high aspect-ratio field emitters composed of CNT-wrapped Ni NT hybrid structures. As a proof of concepts, we demonstrate that high-quality flexible field emission devices can be simply fabricated using our method. Remarkably, our proto-type field emission devices exhibited a current density higher by two orders of magnitude compared to other devices fabricated by previous methods, while maintaining its structural integrity in various bending deformations. This novel fabrication strategy can be utilized in various applications such as optoelectronic devices, sensors and energy storage devices.

Flexible Field Emission Devices Based on Barium Oxide Nanowires

In this work, we report on the fabrication of flexible field emission (FE) devices based on BaO nanostructures synthesized by a chemical bath deposition method. The morphology and composition of BaO nanowires were characterized by FE scanning electron microscopy, high resolution transmission electron microscopy, selected area electron diffraction, X-ray diffraction, and energy dispersive X-ray spectrometer. The results confirmed that BaO nanowires with single crystalline cubic structures grew along the [111] direction. The flexible field emitters fabricated using the BaO nanowires on stainless-steel cylinder substrates show superior FE properties, which exhibited a low turn-on field ( ${\sim}{\hbox{1.24}} {\hbox{V}}/\mu{\hbox{m}}$ ), a low threshold field ( ${\sim}{\hbox{3.18}} {\hbox{V}}/\mu{\hbox{m}}$ ), and a high field enhancement factor $(\beta = 2458)$ . Moreover, the flexible FE devices based on BaO nanowire emitters displayed uniform and bright emission patterns under bending conditions. No obvious degradation of current density was observed during the stability tests. As a result, it is demonstrated that such BaO nanowires are promising for the application in practical flexible FE devices.

All carbon nanotube based flexible field emission devices prepared through a film transfer method

All carbon nanotube based field emission devices were prepared through a vacuum filtering/dry transferring method and the field emission properties of bent devices were systematically studied.

Growth of n-type 3C-SiC nanoneedles on carbon fabric: toward extremely flexible field emission devices

Flexible field emission (FE) arrays have a wide range of applications in next generation low-cost, lightweight and wearable electronics, roll-up displays, and large-area circuits on curved objects, yet the growth of tapered, high-quality single-crystalline nanostructure-based emitters on flexible substrates with superior FE properties remains challenging and related work is limited. On the other hand, our recent studies have shown that silicon carbide (SiC) 1D nanostructures could meet nearly any stringent requirement for an ideal FE emitter. In this contribution, we report the growth of quasi-aligned, single-crystalline n-type doped (N-doped) 3C-SiC nanoneedles (3C-SiCNNs) on highly flexible carbon fabric via the catalyst assisted pyrolysis of polysilazane. The as-synthesized SiCNNs possess a tapered structure with tiny clear tips with sizes of several to tens of nanometers. The fabricated 3C-SiCNNs have extremely low emission turn-on fields (Eon) in the range of 0.5–1.6 V μm−1 with an average of 1.1 V μm−1, which is comparable to the lowest value ever reported for 1D nanostructure emitters that, however, are grown on rigid substrates. Specifically, our SiCNN arrays on carbon fabric are mechanically and electrically robust, and can withstand mechanical bending up to 500 times and still retain excellent FE performance with Eon of ∼1.1 V μm−1. The field-enhancement factor has been calculated to be 6.5 × 103. The superior FE properties can be attributed to the significant enhancements of the tapered unique morphology and N-doping of the SiCNNs. Calculations based on local density functional theory suggest that nitrogen dopants in the 3C-SiC nanostructure could favor a more localized impurity state near the conduction band edge, which improves the electron field emission. We strongly believe that the present work will provide a new insight into the fabrication of flexible field emission arrays with ultralow turn-on fields enhanced by both shape and doping.

Flexible Field Emission from Thermally Welded Chemically Doped Graphene Thin Films

Flexible field-emission devices (FEDs) based on reduced graphene oxide (RGO) emitters are fabricated by the thermal welding of RGO thin films onto a polymeric substrate. The RGO edges are vertically aligned relative to the substrate as a result of cohesive failure in the RGO layer after thermal welding. Even at large bending angles, excellent electron emission properties, such as low turn-on and threshold fields, a high emission current density, a high field enhancement factor, and long-term stability of the emission properties of RGO emitters, arise from the uniform distribution and high density of the extremely sharp RGO edges, as well as the high interfacial strength between the RGO emitters and the substrate. Al- and Au-doped RGO emitters are fabricated by introducing a dopant solution to the RGO emitters, and the resulting field-emission characteristics are discussed. The proposed approach is straightforward and enables the practical use of high-performance RGO flexible FEDs.

Metallic nanowire–graphene hybrid nanostructures for highly flexible field emissiondevices

We report a simple but efficient method to prepare metallic nanowire–graphene(MN–G) hybrid nanostructures at a low temperature and show its application to thefabrication of flexible field emission devices. In this method, a graphene layer wastransferred onto an anodic alumina oxide template, and vertically aligned Au nanowireswere grown on the graphene surface via electrodeposition method. As a proofof concept, we demonstrated the fabrication of flexible field emission devices,where the MN–G hybrid nanostructures and another graphene layer on PDMSsubstrates were utilized as a cathode and an anode for highly flexible devices,respectively. Our field emission device exhibited stable and high field emission currentseven when bent down to the radius of curvature of 25 mm. This MN–G hybridnanostructure should prove tremendous flexibility for various applications such asbio-chemical sensors, field emission devices, pressure sensors and battery electrodes.

Highly transparent and flexible field emission devices based on single-walled carbon nanotube films

Single-walled carbon nanotubes (SWNTs) have been used successfully to fabricate highly transparent and flexible field emission displays (FEDs). Field emission measurements indicated that SWNTs films have great potential to work as building blocks for next generation transparent and flexible FEDs.

Flexible Field Emission of Nitrogen‐Doped Carbon Nanotubes/Reduced Graphene Hybrid Films

The outstanding flexible field emission properties of carbon hybrid films made of vertically aligned N-doped carbon nanotubes grown on mechanically compliant reduced graphene films are demonstrated. The bottom-reduced graphene film substrate enables the conformal coating of the hybrid film on flexible device geometry and ensures robust mechanical and electrical contact even in a highly deformed state. The field emission properties are precisely examined in terms of the control of the bending radius, the N-doping level, and the length or wall-number of the carbon nanotubes and analyzed with electric field simulations. This high-performance flexible carbon field emitter is potentially useful for diverse, flexible field emission devices.

Transfer of patterned vertically aligned carbon nanotubes onto plastic substrates for flexible electronics and field emission devices

A direct transfer method for fabricating flexible electronics without the assistance of an adhesive layer and stamp is reported in this paper. This rapid and simple method provides an approach for the application of vertically aligned carbon nanotubes (VA-CNTs) on plastic substrates. After transfer, the VA-CNTs maintained their initial orientation in the designed pattern and showed sufficient adhesion to the substrate under extreme bending conditions. The flexible device performed an emission on the transparent substrate and showed a low turn-on of 1.13 V/μm. This VA-CNT-based flexible device, which exhibits electrical resistance sensitive to bending, is also described herein.

Aligned Carbon Nanotube−Polymer Hybrid Architectures for Diverse Flexible Electronic Applications

We present the fabrication and electrical characterization of a flexible hybrid composite structure using aligned multiwall carbon nanotube arrays in a poly(dimethylsiloxane) (PDMS) matrix. Using lithographically patterned nanotube arrays, one can make these structures at any length scale from submicrometer levels to bulk quantities. The PDMS matrix undergoes excellent conformal filling within the dense nanotube network, giving rise to extremely flexible conducting structures with unique electromechanical properties. We demonstrate its robustness against high stress conditions, under which the composite is found to retain its conducting nature. We also demonstrate that these structures can be utilized directly as flexible field-emission devices. Our devices show some of the best field-enhancement factors and turn-on electric fields reported so far.