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

Abstract

Vertically aligned carbon nanotubes (CNTs) have proven to be one of the best materials for use as an efficient field emitter. To further improve their efficiency as well as long-term use in practical devices, it is necessary to reduce the quantum resistance originating from the interface between electrode and emitters and the entanglement of the CNTs in a bundle texture. Thus, the incorporation of graphene at the bottom of CNT bundles via a seamless carbonaceous interface can easily solve this bottleneck. In this work we have demonstrated for the first time, growth and field emission properties of pure seamless graphene-CNT heterostructures and pure seamless graphene-vertically patterned oriented CNTs heterostructures (SGVCNTs) on Si/SiO2 substrates in contrast to the bare CNT mats and few-layer graphene structures without using any tedious post transfer processes. It was observed that seamless SGVCNTs show better field emission performance in terms of higher current density (236 mA cm−2), lowered turn-on field (0.45 V μm−1) and threshold field (1.931 V μm−1 @100 mA cm−2), and improved field enhancement factor (β ∼ 41 315) which is improved ∼4 fold when compared to a bare CNT mat. The significant improvement of the field emission performance of SGVCNTs is mainly attributed to the low resistive seamless C–C covalent carbonaceous interface, the higher number of emitter sites and patterned vertical orientation that leads to long-term stability of the field emitter with minimal loss up to 32 h. This finding could provide an important solution for carbonaceous material based field emitters for real phase device applications.

Super-Hydrophilic Hierarchical Ni-Foam-Graphene-Carbon Nanotubes-Ni2P–CuP2 Nano-Architecture as Efficient Electrocatalyst for Overall Water Splitting

“…It is hard to grow high-density CNTs on top of the bare Ni-foam using a Fe catalyst due to the diffusion of Fe in a Ni substrate with a high-temperature CVD technique without any barrier layers. Here, graphene works as an antidiffusion layer against the Fe catalyst and helps to grow CNTs via the formation of a seamless interface between graphene and CNTs. , This seamless interface not only provides a high surface area but also creates a smooth conducting electrical path for the exotic electron transfer process in the electrochemical reaction. Thereafter, electrochemically Ni was deposited (Figure S4a) uniformly on the CNT matrix (details analysis in Figure S5) followed by phosphorization to grow Ni 2 P anchored on the surface of CNT bundles, creating a 3D porous Ni-graphene-CNTs-Ni 2 P (NGCN) heterostructure (Figure c).…”

“…It is observed that the majority of the peaks are shifted (2θ ∼ 0.03°–0.2°) because of the interfacial strain induced in the geometry and small lattice mismatch due to the formation of the heterostructure. , A similar type of observation has also been noticed in the Raman analysis of the heterostructure (Figure S9). The Raman spectra of NGCNC refer to the presence of D- (1343.42 cm –1 ), G- (1577.22 cm –1 ), and 2D- (2688.11 cm –1 ) bands, reflecting the existence of a graphene/CNTs matrix. , The D band arises due to the defect and structural disorder of the carbon matrix, which is ascribed to the A 1g mode of vibration; the G-band corresponds to the E 2g vibration mode of C–C bond stretching, and the 2D-band is the overtone of a D-band, which is a result of double resonance between the K-points in the Brillouin zone. , However, the peaks have been shifted toward a lower wavenumber as compared to Ni-Gr-CNTs, indicating the charge transfer between the carbon matrix and the metal phosphide. In addition, the increase of the I D / I G ratio from 0.85 to 1.05 in NGCNC reveals that more disorder and defects have been incorporated in the carbon matrix due to the deposition of metal phosphide on top of the Ni-Gr-CNTs heterostructure .…”

“…The Raman spectra of NGCNC refer to the presence of D-(1343.42 cm −1 ), G-(1577.22 cm −1 ), and 2D-(2688.11 cm −1 ) bands, reflecting the existence of a graphene/CNTs matrix. 18,46 The D band arises due to the defect and structural disorder of the carbon matrix, which is ascribed to the A 1g mode of vibration; the G-band corresponds to the E 2g vibration mode of C−C bond stretching, and the 2D-band is the overtone of a Dband, which is a result of double resonance between the K-points in the Brillouin zone. 46,48 However, the peaks have been shifted toward a lower wavenumber as compared to Ni-Gr-CNTs, indicating the charge transfer between the carbon matrix and the metal phosphide.…”

A Critical Review of the Role of Carbon Nanotubes in the Progress of Next-Generation Electronic Applications

“…An approach by Riyajuddin, 39 in which seamless pure graphene and a vertically grown CNT heterostructure (SGVCNT) was developed using thermal CVD and plasma-enhanced CVD. As the structure aligned vertical CNTs, the length and diameter were recorded to be about 55–60 µ m and 5–6 µ m. The heterostructure was placed on a non-active Si/SiO 2 substrate and checked for field emission properties.…”

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].…”