The Characteristics of Carbon Nanotubes with Electroless Plating Deposited Ni Catalysts
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The Characteristics of Carbon Nanotubes with Electroless Plating Deposited Ni Catalysts C.S. Huang*, B.R. Huang, C.Y. Lin, C.C. Wu , T.E. Yu Department and Institute Electronic Engineering, National Yunlin University of Science and Technology, Taiwan, ROC ABSTRACT We have synthesized multi-walled carbon nanotubes (MWNTs) on nickel-deposited n-type silicon substrates by thermal chemical vapor deposition (Thermal CVD). The electroless plating method was adopted in the deposition of the Ni catalytic layer. Sulfuric acid solution was used as a buffer to adjust and maintain a pH value of 4.6. Both the deposition time of the nickel catalyst layer and the growth time of MWNTs were adopted to control the length and density of MWNTs. Scanning electron microscopy (SEM) images showed that the density of carbon nanotubes increased as the deposition time of nickel catalyst layer increased. The formation of nickel nucleation becomes rich as the immersion time of the substrate in electroless plating solution was longer, and this benefited the growth of carbon nanotubes. In addition, the Raman spectrum demonstrated that the ID/IG ratio of MWNTs decreases as the deposition and growth time increase, indicating that more graphene MWNT structures were formed. INTRODUCTION Carbon nanotubes (CNTs), since their discovery in 1991 [1], have been considered for use in many different applications. Various synthesize methods of CNTs such as arc-discharge [2], pyrolysis [3], microwave plasma enhance chemical vapor deposition (MPCVD) [4] and thermal chemical vapor deposition (thermal CVD) [5] have been developed. The small dimensions, strength and remarkable physical properties of these materials make them the very promising emitters for field emission devices. Field emission devices based on CNTs have exhibited remarkable emission characteristics and good current stability [6,7], because of the high-aspect-ratio and electrical conductivity, as well as a mechanical stiffness of the nanotubes [8,9]. Catalysts are normally used for CNTs growth by decomposing a hydrocarbon source. The catalyst layer can be deposition using various methods, such as sputtering [10-11], evaporators [12-13], sol-gel [14] and so on. However, these method costs more deposition time and the capital of production. Here, we demonstrate a very simple method for deposition catalyst layer by electroless plating. The electroless plating method was adopted in the deposition of the Ni catalytic layer on n-type silicon substrate [15-17], and we have synthesized multi-walled carbon nanotubes (MWNTs) on nickel-deposited n-type silicon substrates by thermal chemical vapor deposition. EXPERIMENTAL DETAILS The multi-walled carbon naotubes (MWNTs) were synthesized on n-type silicon substrate using a thermal chemical vapor deposition system. Prior to MWNTs growth, different thickness of the nickel catalyst layer was deposited by electroless plating method. The procedure of electroless plating can be divided into three steps: activation, sensitization and plating. The silicon sub
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