Abstract

Multi-walled carbon nanotubes (MWCNTs) grown by chemical vapor deposition retain the residual catalyst particles from which the growth occurred, which are considered a detriment to MWCNTs’ performance, especially electrical conductivity. The first direct measurements have been made of the electrical transport through the catalyst cap into the MWCNT using nanoscale 2-point-probe to determine the effects of the catalyst particle’s size and the diameter ratio with its associated MWCNT on the electrical transport through the catalyst cap as compared to the inherent conductivity of the MWCNT. The MWCNT diameter is independent of the catalyst size, but the ratio of the catalyst cap diameter to MWCNT diameter (D_C/D_NT) determines the conduction mechanism. Where D_C/D_NT is greater than 1 the resulting I–V curve is near ohmic, and the conduction through the catalyst (R_C+NT) approaches that of the MWCNT (R_NT); however, when the D_C/D_NT < 1 the I–V curves shift to rectifying and R_C+NT > > R_NT. The experimental results are discussed in relation to current crowding at the interface between catalyst and nanotube due to an increased electric field.

Graphic abstract

中文翻译：

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催化剂-多壁碳纳米管结的尺寸依赖性导电特性

摘要

通过化学气相沉积生长的多壁碳纳米管（MWCNT）保留了从中发生生长的残留催化剂颗粒，这被认为是对MWCNTs性能（尤其是导电性）的损害。首次直接测量是使用纳米级两点探针通过催化剂帽进入MWCNT的电传输，以确定催化剂颗粒尺寸和直径比及其相关的MWCNT对通过催化剂帽的电传输的影响与MWCNT的固有电导率相比。MWCNT的直径与催化剂的尺寸无关，但是催化剂盖直径与MWCNT直径的比值（D _C / D _NT）决定了导电机理。哪里D _C / D _NT大于1时，所得的I – V曲线接近欧姆，并且通过催化剂的传导（R _{C + NT}）接近MWCNT（R _NT）。但是，当D _C / D _NT  <1时，I – V曲线向整流方向移动，并且R _{C + NT}  >>  R _NT。讨论了由于电场增加导致电流在催化剂和纳米管之间的界面拥挤的实验结果。

图形摘要