Measurements of CNT Forest Self-Assembly from In-situ ESEM Synthesis

Understanding the dynamic self-assembly mechanisms of carbon nanotube (CNT) forests is necessary to advance their technological promise. Here, in-situ environmental scanning electron microscope (ESEM) chemical vapor deposition (CVD) synthesis observes the real-time nucleation, assembly, delamination, and self-termination of dense (> 10^9 CNT/cm^2), tall (> 100 μm) CNT forests in real time. Forest synthesis is continuously observed from nucleation to self-termination. Assembly forces generated near the substrate detach CNTs from the substrate, which simulation suggests requires approximately 10 nN of tensile force. Delamination initiates at both the CNT-catalyst and the catalyst-substrate interfaces, indicating multiple delamination mechanism. Digital image correlation applied to SEM image sequences measures time-invariant strain within growing forests, indicating that forests grow as rigid bodies after liftoff. The Meta CoTracker algorithm measured CNT growth rates reduce from 50 nm/sec to full termination over 150 seconds. This work provides a robust strategy to observe and measure CVD material synthesis in-situ using ESEM. The method is uniquely suited to observe population-based phenomena at both nanometer spatial resolution and at a highly scalable field of view.