Multiscale Characterization and Two‐Stage Assembly Mechanism of Dimension‐Limited Self‐Aligned Carbon Nanotube Arrays

ABSTRACT

High‐density, semiconducting aligned carbon nanotube arrays (A‐CNTs) are essential for next‐generation electronics. Dimension‐limited self‐alignment (DLSA) is a leading route to wafer‐scale A‐CNT fabrication, yet the instabilities that limit array quality remain poorly understood, hampering targeted process optimization. Here, we establish a multiscale characterization framework combining cross‐polarized optical microscopy (xPOM) and scanning electron microscopy (SEM) to evaluate DLSA‐prepared A‐CNT wafers and identify the underlying film‐formation mechanism. Notably, characterization of the entire 4‐inch wafer is achieved within approximately 1 h, providing an efficient route for high‐throughput macroscopic inspection. Cross‐validation across multiple characterization methods reveals a hierarchical morphology comprising four spatial regions and recurring macroscopic defects. These observations, together with in situ measurements of DLSA dynamics, support a two‐stage self‐assembly mechanism: initial two‐dimensional biphasic self‐assembly behavior followed by quasi‐one‐dimensional triphasic self‐assembly coupled to continuous transfer. The second stage, imposed by orientational confinement at the air/top‐layer/CNT‐dispersion interface, is proposed to drive globally consistent alignment. Specific defects are further associated with distinct kinematic processes and mechanical stress states. This mechanistic picture provides a framework for suppressing non‐idealities in A‐CNTs and supporting their eventual integration into CNT‐based logic circuits.