Shanliang Chen

Large-Scale Growth of Well-Aligned SiC Tower-Like Nanowire Arrays and Their Field Emission Properties

Fabrication of well-aligned one-dimensional (1D) nanostrucutres is critically important and highly desired since it is the key step to realize the patterned arrays to be used as the display units. In the present work, we report the large-scale and well-aligned growth of n-type SiC nanowire arrays on the 6H-SiC wafer substrates via pyrolysis of polymeric precursors assisted by Au catalysts. The obtained n-type SiC nanowires are highly qualified with sharp tips and numerous sharp corners around the wire bodies, which bring the emitters excellent field emission (FE) performance with low turn-on fields (1.50 V/μm), low threshold fields (2.65 V/μm), and good current emission stabilities (fluctuation <3.8%). The work abilities of the n-type SiC tower-like nanowire arrays under high-temperature harsh environments have been investigated, suggesting that the resultant field emitters could be well serviced up to 500 °C. The temperature-enhanced FE behaviors could be attributed to the reduction of the work function induced by the rise of temperatures and the incorporated N dopants. It is believed that the present well-aligned n-type SiC tower-like nanowire arrays could meet nearly all stringent requirements for an ideal FE emitter with excellent FE properties, making their applications very promising in displays and other electronic nanodevices.

Temperature-dependent field emission of flexible n-type silicon carbide nanoneedle emitters

In this work, we reported the temperature-dependent field emission (FE) of flexible n-type SiC nanoneedles grown on the carbon fabric substrates via pyrolysis of polymeric precursor. The obtained n-type SiC nanoneedles with clear and sharp tips were incorporated by N dopants with a uniform spatial distribution. The FE behaviors of n-type SiC nanoneedles exhibit a strong dependence on the temperatures. Their turn-on fields and threshold fields decrease from 1.37 to 0.67 V/μm and 1.87 to 0.96 V/μm with the temperature raised from room temperature (RT) to 400 °C, respectively. The measured current emission stabilities of the n-type SiC nanoneedles under RT and 200 °C are ∼7.7% and 14.1%, respectively. The temperature-dependent FE characteristics could be attributed to the reduction of the work function of n-type SiC nanoneedles induced by the raise of temperatures and the incorporated N dopants.

Nanowire-density-dependent field emission of n-type 3C-SiC nanoarrays

The density of the nanowires is one of the key issues for their field emission (FE) properties of the nanoarrays, since it plays an important role on the electron emission sites and field screening effect. Here, we reported the nanowire-density-dependent FE properties of the n-type 3C-SiC nanoarrays. The highly oriented and large-scale SiC nanoarrays were grown on the 6H-SiC wafer via pyrolysis of polyureasilazane by adjusting the thicknesses of Au films used as the catalysts. The densities of the nanoarrays were tunable to be ∼2.9 × 107, ∼4.0 × 107, and ∼5.7 × 107 nanowires/cm2 by controlling the Au film thicknesses of 50, 70, and 90 nm, respectively. The measured FE characteristics disclosed that the turn-on fields of the samples could be tailored to be of ∼1.79, 1.57, and 1.95 V/μm with the increase of the densities, suggesting that a suitable nanowire density could favor the enhanced electron emission from the SiC nanoarrays with improved emission sites and limited field screening effects.

Current emission from P-doped SiC nanowires with ultralow turn-on fields

In the present work, we reported the current emission from P-doped SiC nanowire field emitters, which were synthesized via catalyst-assisted pyrolysis of polysilazane precursors. Directed by F–N theory for enhanced field emission (FE) behaviors, the emitters were grown into nanostructures with two desired characteristics, namely with an ultrahigh aspect ratio as well as incorporated P dopants, which brought profound enhancements to the field enhancement factor (β) and turn-on field (Eto). The as-grown SiC nanowires (SiCNWs) exhibit an aspect ratio over 1500 with a uniform spatial distribution of P dopants. The FE measurements exhibit that the SiCNWs possessed a field enhancement factor up to 11657 and an ultralow Eto of 0.47 V μm−1, which was little achieved among the reported studies. The current emission fluctuations are ∼±4.0% over 5 h, suggesting their good electron emission stability. We mainly attributed the totally excellent FE performances to the ultra-high aspect ratio and the incorporated P dopants of the obtained SiCNWs, which could synergistically cause a significant increase of the field enhancement factor and a decrease of the work function.

A giant negative piezoresistance effect in 3C-SiC nanowires with B dopants

Silicon carbide (SiC) is recognized as a promising substitute for the currently used Si for exploring robust pressure sensors with desired high sensitivities and excellent abilities to serve under harsh work conditions. In the present work, we reported the giant piezoresistance effect of p-type 3C-SiC nanowires with B dopants, which were synthesized by catalyst-assisted pyrolysis of polysilazane. The transverse electromechanical properties of SiC nanowires were investigated at loading forces applied using a conductive atomic force microscopy (C-AFM) tip. The resistances of the as-synthesized SiC nanowires exhibit an increase with the increase of compressed stresses at the same bias voltages, representing their negative piezoresistance behaviors. The measured negative piezoresistance coefficient π[10] of the nanowire fell in the range of −8.83 to −103.42 × 10−11 Pa−1 as the applied loading forces ranged from 51.7 to 181.0 nN. The giant gauge factor (GF) could be up to −620.5, which was enhanced by more than 10 times compared to the highest ever reported for SiC nanostructures.

Enhanced field emission of Au nanoparticle-decorated SiC nanowires

Silicon carbide (SiC) nanostructures are considered as an excellent candidate for field emitters, owning to their versatile superior properties. The field emission with a low turn-on field (Eto) is crucial and highly desired for their practical application. In the present study, SiC nanowires (SiCNWs) were grown on carbon fabrics via the pyrolysis of a polymeric precursor, followed by surface decoration with Au nanoparticles by a sputtering process. The characterizations of their field emission (FE) properties revealed that the Au nanoparticle-decorated SiC nanowires exhibit remarkably enhanced FE performances. Compared to those of the bare counterparts (i.e., without the Au nanoparticle decoration), the Eto of Au decorated SiCNWs was decreased drastically from 2.10 to 1.14 V μm−1. The field enhancement factor (β) of the Au decorated SiCNWs was ca. 6244 ± 50, which is nearly 6 times that of the bare counterparts. The enhanced FE behaviors were mainly attributed to the synergistically increased β and decreased Φ of the SiCNWs induced by Au decoration.

Nanoparticle-density-dependent field emission of surface-decorated SiC nanowires

Increasing the electron emission site density of nanostructured emitters with limited field screening effects is one of the key issues for improving the field emission (FE) properties. In this work, we reported the Au-nanoparticles-density-dependent field emission behaviors of surface-decorated SiC nanowires. The Au nanoparticles (AuNPs) decorated around the surface of the SiC nanowires were achieved via an ion sputtering technique, by which the densities of the isolated AuNPs could be adjusted by controlling the fixed sputtering times. The measured FE characteristics demonstrated that the turn-on fields of the SiC nanowires were tuned to be of 2.06, 1.14, and 3.35 V/μm with the increase of the decorated AuNPs densities, suggesting that a suitable decorated AuNPs density could render the SiC nanowires with totally excellent FE performances by increasing the emission sites and limiting the field screening effects.

Fabrication of highly oriented 4H-SiC gourd-shaped nanowire arrays and their field emission properties

The growth of highly oriented one-dimensional (1D) nanoarrays is critically important and highly desired, since it is one of the fundamental issues to push forward their applications in field emitters. In the current work, we reported the large-scale fabrication of highly oriented 4H-SiC gourd-shaped nanowire arrays with numerous sharp knots around the wire surface, which could be an ideal structural configuration for the exploration of emitters. The nanoarrays were prepared via an electrochemical anodic oxidation process assisted by pulsed voltage at room temperature (RT) and under atmospheric pressure. The formation of the gourd-shaped nanowires was mainly ascribed to the applied pulsed voltage, which caused the etching reaction, happened periodically and made the fluctuation of the diameters. Their measured field emission (FE) characteristics disclosed that the gourd-shaped SiC nanowire arrays had a low turn-on field of 0.95 V μm−1, implying their good FE performances. The current emission fluctuations at RT and 200 °C are measured to be ∼±2.1 and ±2.8%, respectively, suggesting that they are robust to be serviced at high temperatures.

Flexible low-dimensional semiconductor field emission cathodes: fabrication, properties and applications

Flexible field emission cathodes, as a member of the class of flexible electronic nanodevices, have potential applications in flexible displays and miniature X-ray tubes. In the present review, we first provide an overview of the research progress made in this field, focusing on the fabrication and field emission properties of flexible field emission cathodes based on low-dimensional inorganic semiconductor nanostructures, which are typically grown on flexible substrates, such as polymers, graphene and carbon fabrics. After this, we provide a brief introduction to the major features of flexible field emission cathodes. Subsequently, we shed some light on their potential applications in field emission displays and X-ray tubes. Finally, we discuss future prospects in the further development of flexible field emission cathodes.

Superior B-Doped SiC Nanowire Flexible Field Emitters: Ultra-Low Turn-On Fields and Robust Stabilities against Harsh Environments

Low turn-on fields together with boosted stabilities are recognized as two key factors for pushing forward the implementations of the field emitters in electronic units. In current work, we explored superior flexible field emitters based on single-crystalline 3C-SiC nanowires, which had numbers of sharp edges, as well as corners surrounding the wire body and B dopants. The as-constructed field emitters behaved exceptional field emission (FE) behaviors with ultralow turn-on fields (Eto) of 0.94-0.68 V/μm and current emission fluctuations of ±1.0-3.4%, when subjected to harsh working conditions under different bending cycles, various bending configurations, as well as elevated temperature environments. The sharp edges together with the edges were able to significantly increase the electron emission sites, and the incorporated B dopants could bring a more localized state close to the Fermi level, which rendered the SiC nanowire emitters with low Eto, large field enhancement factor as well as robust current emission stabilities. Current B-doped SiC nanowires could meet all essential requirements for an ideal flexible emitters, which exhibit their promising prospect to be applied in flexible electronic units.