Affiliation:
1. Department of Mechanical Engineering, The University of Tokyo, Tokyo 113-8656, Japan
2. Energy NanoEngineering Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8564, Japan
Abstract
A catalyst is essential for the controlled synthesis of single-walled carbon nanotubes (SWNTs) by chemical vapour deposition (CVD). However, it is difficult to observe these nanosized particles in their original forms and in a statistical manner, which has resulted in a vague understanding of the behaviours of these particles. We present a technique to solve this long-standing issue. The key is to have an MEMS fabricated suspended SiO
2
layer, which is thick enough to support catalyst deposition and nanotube growth but thin enough to allow electron beams to transit. On a 20 nm SiO
2
film, we confirm that catalyst can be observed at an atomic resolution, and the catalyst–SWNT junctions can also be routinely observed. As a demonstration of this technique, we revisited the behaviour of monometallic catalysts through a systematic investigation of the size, chemical state and crystal structure of particles before and after high-temperature CVD. The active catalyst is found to follow a tangential growth mode, while the inactive catalyst is divided into three mechanisms: size growth, metal loss and inappropriate precipitation. The latter two mechanisms were not possible to observe by previous techniques.
Funder
Japan Society for the Promotion of Science
Cited by
14 articles.
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