Riyajuddin Sk, Kumar Sushil, Soni Khushboo, Gaur Surender P, Badhwar Damini, Ghosh Kaushik
Institute of Nano Science and Technology, Mohali, Punjab, 160062, India.
Nanotechnology. 2019 Sep 20;30(38):385702. doi: 10.1088/1361-6528/ab1774. Epub 2019 Apr 9.
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/SiO 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), lowered turn-on field (0.45 V μm) and threshold field (1.931 V μm @100 mA cm), 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.
垂直排列的碳纳米管（CNTs）已被证明是用作高效场发射体的最佳材料之一。为了进一步提高其效率以及在实际器件中的长期使用性能，有必要降低源自电极与发射体之间界面的量子电阻以及碳纳米管束状结构中的缠结。因此，通过无缝碳质界面在碳纳米管束底部引入石墨烯可以轻松解决这一瓶颈。在这项工作中，我们首次展示了在Si/SiO₂ 衬底上生长的纯无缝石墨烯 - 碳纳米管异质结构和纯无缝石墨烯 - 垂直图案化定向碳纳米管异质结构（SGVCNTs）的生长和场发射特性，与裸碳纳米管垫和少层石墨烯结构形成对比，且未使用任何繁琐的后转移工艺。据观察，无缝SGVCNTs在更高的电流密度（236 mA/cm²）、更低的开启场（0.45 V/μm）和阈值场（1.931 V/μm @100 mA/cm²）以及更高的场增强因子（β ∼ 41315）方面表现出更好的场发射性能，与裸碳纳米管垫相比，场增强因子提高了约4倍。SGVCNTs场发射性能的显著提高主要归因于低电阻的无缝C - C共价碳质界面、更多的发射位点以及图案化的垂直取向，这导致场发射体具有长期稳定性，在长达32小时的时间内损失最小。这一发现可为基于碳质材料的场发射体在实际器件应用中提供重要解决方案。
