Water-processed carbon nanotube/graphene hybrids with enhanced field emission properties

Abstract

Integrating carbon nanotubes (CNTs) and graphene into hybrid structures provides a novel approach to three dimensional (3D) materials with advantageous properties. Here we present a water-processing method to create integrated CNT/graphene hybrids and test their field emission properties. With an optimized mass ratio of CNTs to graphene, the hybrid shows a significantly enhanced field emission performance, such as turn-on electric field of 0.79 V/μm, threshold electric field of 1.05 V/μm, maximum current density of 0.1 mA/cm2, and field enhancement factor of ∼1.3 × 104. The optimized mass ratio for field emission emphasizes the importance of both CNTs and graphene in the hybrid. We also hypothesize a possible mechanism for this enhanced field emission performance from the CNT/graphene hybrid. During the solution treatment, graphene oxide behaves as surfactant sheets for CNTs to form a well dispersed solution, which leads to a better organized 3D structure with more conducting channels for electron transport.

Study of field emission properties of pure graphene-CNT heterostructures connected via seamless interface

“…SGVCNTs show higher current density than SGCNTs, which is due to the minimized screening effect. Here in our samples, the E th is defined as the field required to emit a current density of 0.1 A cm −2 [46] and the E th value of SGVCNTs was found to be 1.931 V μm −1 which is ∼1.5 and ∼1.2 times lower than CNTs and SGCNTs heterostructures, respectively (shown in figure S3(b)).…”

“…where J is the macroscopic current density, f is the emitter's local work function, E is the applied electric field, β is the field enhancement factor, N is the density of the emission sites, α is the average area of the emission sites, a and b are known as the first and second FN constants and their values are 1.54×10 −6 AeV/V 2 and 6.83×10 7 eV −3/2 V/cm, respectively [45]. As the work function (f) of graphene and CNTs are the same (f=5.0 eV), we have chosen the work function of the SGCNTs heterostructure f=5.0 eV [46,47]. Figure 5(a) shows emitter average current density (J) versus electric field (E) plots of FLG, CNTs, SGCNTs and, SGVCNTs.…”

“…Here SGVCNTs show lower E th in comparison with the other samples. The E on is defined as field required to emit the current density of 10 μA cm −2 [17,46], which is coming out to be 1.89, 1.2, 0.78, 0.45 V μm −1 for FLG, CNTs, SGCNTs and SGVCNTs, respectively (shown in figure S3(a)). From these analyses it is realized that the E on of SGVCNTs is ∼4 times lower than that of FLG and ∼3 times lower than non-vertical CNTs which is due to the small apex curvature, high specific surface, high aspect ratio, nanometer-sized tip radii [19,20].…”

Графен/Нанотрубные Квази-1d-Структуры В Сильных Электрических Полях

“…В последние годы одним из перспективных направлений развития исследований в области графен-УНТ соединений является получение композитных материалов с улучшенными эмиссионными характеристиками для последующего применения в качестве наноэмиттеров [49][50][51][52][53][54]. Одним из последних достижений в этой области стало экспериментальное получение методом электрофоретического осаждения гибридных пленок ОУНТ/графен, демонстрирующих максимальный эмиссионный ток величиной 80 mA с соответствующей плотностью тока 160 mA/cm 2 при напряженности электрического поля 9.6 V/µm [54].…”

Graphene/nanotube quasi-1D structures in strong electric fields

“…In recent years, one of the promising areas of graphene-CNT research included production of composite materials with improved emission characteristics for further use as nano-emitters [49][50][51][52][53][54]. One of the latest achievements in this area was the experimental electrophoretic deposition of SWCNT/graphene hybrid films demonstrating the maximum emission current of 80 mA with the corresponding current density of 160 mA/cm 2 at an electric field strength of 9.6 V/µm [54].…”