Field Emission of Multi-Walled Carbon Nanotubes from Pt-Assisted Chemical Vapor Deposition

Hongbin Tang,Ruizi Liu,Weijin Qian,Wei Zhu,Weijun Huang,Changkun Dong

doi:10.3390/nano12030575

Abstract

Multi-walled carbon nanotubes (MWNTs) were grown directly on a metal substrate with the assistance of Pt using a chemical vapor deposition method. In addition, the growth mechanism of Pt-assisted catalytic CNT was discussed. MWNTs were characterized by SEM, TEM, AFM, Raman, and EDS, and the field emission (FE) properties were investigated, comparing with the direct grown MWNTs. The results showed that CNTs could not been synthesized by Pt particles alone under the experimental condition, but Pt may accelerate the decomposition of the carbon source gas, i.e., assisting MWNT growth with other catalysts. The Pt-assisted MWNTs were longer with larger diameters of around 80 nm and possessed better structural qualities with very few catalyst particles inside. Improved field emission properties were demonstrated for the Pt-assisted MWNTs with lower turn-on fields (for 0.01 mA·cm−2 current density) of 2.0 V·μm−1 and threshold field (for 10 mA·cm−2 current density) of 3.5 V·μm−1, as well as better stability under a long-term test of 80 h (started at 3.0 mA for the Pt-assisted emitter and 3.25 mA for the direct grown emitter). This work demonstrated a promising approach to develop high performance CNT field emitters for device applications.

Highlights

Due to unique structural, chemical, and physical properties, carbon nanotubes (CNTs) have been applied and investigated in various areas [1,2,3,4]
Random orientation and good homogeneity are favorable for reducing emission hot spots and the edge effect from local excessive Joule heating under high emission to burn the long CNT
More catalyst particles were detected along direct growth Multi-walled carbon nanotubes (MWNTs), especially inside the caps

Summary

Introduction

Chemical, and physical properties, carbon nanotubes (CNTs) have been applied and investigated in various areas [1,2,3,4]. With the advantages of large aspect ratio, high electrical conductivity, and good thermal stability, CNTs present excellent field emission properties for different types of vacuum electronic devices [5,6,7]. In most CVD synthesis, carbon nanotubes are grown from the catalyst films, e.g., Fe, Co, and Ni, and deposited on the substrates [8,9]. Terrado et al prepared uniform multi-walled carbon nanotubes by spraying precipitated Co catalyst particles on quartz substrates and discussed the effects of catalyst pretreatment and growth temperature on CNT diameters [11]. The direct growth of CNTs on metallic substrates containing catalyst elements exhibited significant advantages, including the enhancement of adhesion and reduction in contact resistance between CNTs and the substrates, resulting in improvements in field emission properties. Beyond typical single element catalyst (e.g., Fe, Co, Ni, etc.), multi-element catalysts, such as Ni alloys, have been found to present prominent catalytic effects for CNT synthesis [5,15,16,17]

Methods

Results

Conclusion