Enhanced electron emission from tetrahedral amorphous carbon capped carbon nanotube core-shelled structure

• Published in: Diamond and related materials 2012, Vol.21, p.37-41
• Main Authors: Yu, Jun, Anetab, Pruthvi, Koh, Angel Ting Ting, Chua, Daniel H.C., Wei, Jun
• Format: Article
• Language: English
• Subjects: Amorphous structure; Arrays; Carbon; Carbon nanotubes; Core–shell; Cross-disciplinary physics: materials science; rheology; Electron emission; Exact sciences and technology; Laser deposition; Lithography; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Methods of nanofabrication; Nanoscale materials and structures: fabrication and characterization; Nanoscale pattern formation; Nanotubes; Other topics in nanoscale materials and structures; Physics; Tantalum; Thickness
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2011.10.006

Core-shelled composites have been shown to enhance material properties, notably for chemical sensing and biomolecular applications. In this comprehensive study, we show that a simple core–shell structure, made up of tetrahedral amorphous carbon (ta-C) tip-capped onto an aligned dense array of carbon nanotubes (CNT), exhibits superior electron emission properties, having a distinct enhancement in the turn-on field of < 1 V/μm without any lithography patterning. This is compared to ~ 2 V/μm for pristine CNT samples. A KrF pulsed laser deposition process was used to deposit high (> 70%) sp 3 content non-hydrogenated ta-C films of varying thickness for the tip-capping process. Combining scanning electron microscopy images and electron emission testing results, our systematic study shows that first, the thickness of the ta-C can range from 20 to 100 nm and is sufficient to achieve the enhancement effect. However, thicker coatings > 200 nm will degrade the electron emission. Second, a simple tip-capping is sufficient to achieve the enhancement without the need to encapsulate the entire carbon nanotube. ► A core–shell structure was fabricated by tip-capping CNTs with ta-C. ► Field emission properties of CNTs with and without coatings were examined. ► A distinct enhancement on field emission was obtained with ta-C coatings. ► Ta-C thickness of 20–100 nm is sufficient to achieve the enhancement. ► Thicker ta-C coatings > 200 nm will degrade the electron emission.