Quantum confinement effect and field emission characteristics of ultrathin 3C–SiC nanobelts

Stable Field Emission from Vertically Oriented SiC Nanoarrays

Silicon carbide (SiC) nanostructure is a type of promising field emitter due to high breakdown field strength, high thermal conductivity, low electron affinity, and high electron mobility. However, the fabrication of the SiC nanotips array is difficult due to its chemical inertness. Here we report a simple, industry-familiar reactive ion etching to fabricate well-aligned, vertically orientated SiC nanoarrays on 4H-SiC wafers. The as-synthesized nanoarrays had tapered base angles >60°, and were vertically oriented with a high packing density >107 mm-2 and high-aspect ratios of approximately 35. As a result of its high geometry uniformity-5% length variation and 10% diameter variation, the field emitter array showed typical turn-on fields of 4.3 V μm-1 and a high field-enhancement factor of ~1260. The 8 h current emission stability displayed a mean current fluctuation of 1.9 ± 1%, revealing excellent current emission stability. The as-synthesized emitters demonstrate competitive emission performance that highlights their potential in a variety of vacuum electronics applications. This study provides a new route to realizing scalable field electron emitter production.

Wetting Behavior of Metal-Catalyzed Chemical Vapor Deposition-Grown One-Dimensional Cubic-SiC Nanostructures

Superhydrophobic surfaces can be fabricated by using the self-assembled nanoarchitecture of 3C-SiC one-dimensional (1D) nanostructures as they are capable of forming a dense network of micro-nano air pockets without any help from external sources. Herein, the metal-catalyzed growth of 3C-SiC nanowires/nanorods on Si substrates via vapor-liquid-solid mechanism using five different catalysts, that is, chemically synthesized Au nanoparticles and direct current-sputtered thin films of Au, Cu, Ni, and Ti, is reported. Relatively new or unexplored catalysts such as thin films of Cu and Ti, as well as drop-cast Au nanoparticles, were used. An optimized and separate growth was carried out for each catalyst in an inductively heated horizontal cold-wall atmospheric pressure chemical vapor deposition reactor. An insight into the catalytic growth mechanism of 3C-SiC 1D nanostructures has been presented. All of the bare samples exhibited superhydrophilic behavior, whereas hierarchical Au/Pd nanostructure-coated 3C-SiC nanorod samples grown using Au and Ni thin-film catalysts exhibited hydrophobic and superhydrophobic behavior, respectively. As the better results were obtained for Ni thin-film catalysts in terms of growth density and high water contact angle (WCA ≈ 160°), therefore, the growth temperature, as well as the growth time-dependent wetting behavior, was also studied. It was found that the WCA increased as the growth time and temperature increased because of the increase in the growth density, and it finally reached to an optimum value at the growth temperature of 1200 °C and the growth time of 1 h. Furthermore, their wetting behavior was studied by using a variety of high surface tension (water, milk, tea, and glycerin) and low surface tension (organic liquids such as n-hexane, ethanol, etc.) liquids. High surface tension liquids exhibited superhydrophobic behavior, whereas low surface tension liquids exhibited superhydrophilic behavior. Hence, these fabricated nanostructured surfaces can be exploited for oil-water separation, electrowetting, water harvesting, self-cleaning, lab on a chip, and micro-/nanofluidic device applications.

High-temperature stable field emission of B-doped SiC nanoneedle arrays

Current emission stability is one of the key issues for field emitters for them to be practically applied as electron sources. In the present work, large-scale and well-aligned B-doped SiC nanoneedle arrays have been grown on 6H-SiC wafer substrates via pyrolysis of polymeric precursors. The measured field emission (FE) characteristics suggest that the turn-on fields of the as-synthesized SiC nanoneedle arrays are reduced from 1.92 to 0.98 V μm(-1) with temperature increasing from room temperature (RT) to 500 °C, suggesting their excellent FE performances. The slightly changed current fluctuations (only ∼1.3%) between RT and 200 °C confirm that the present SiC nanoarrays with B dopants could be highly stable field emitters to be used in service under harsh conditions of high temperatures.

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.

Diverse Role of Silicon Carbide in the Domain of Nanomaterials

Silicon carbide (SiC) is a promising material due to its unique property to adopt different crystalline polytypes which monitor the band gap and the electronic and optical properties. Despite being an indirect band gap semiconductor, SiC is used in several high-performance electronic and optical devices. SiC has been long recognized as one of the best biocompatible materials, especially in cardiovascular and blood-contacting implants and biomedical devices. In this paper, diverse role of SiC in its nanostructured form has been discussed. It is felt that further experimental and theoretical work would help to better understanding of the various properties of these nanostructures in order to realize their full potentials.