Advances in Highly Aligned and Ultraclean Horizontal Carbon Nanotube Arrays

Carbon nanotubes (CNTs) are promising materials for next-generation electronics, serving as channel materials, electrical contacts, or interconnects due to their exceptional electronic properties. To fully realize their potential, it is crucial to achieve well-aligned CNT arrays for superior charge transport. High degree of alignment and ultraclean surface are two foundational metrics for high-performance CNT arrays, as they directly impact charge transport efficiency and device reliability. However, achieving these attributes remains a significant challenge. In this Perspective, we provide a critical evaluation and a comparative analysis of four principal fabrication paradigms: (1) liquid-phase assembly, (2) chemical vapor deposition (CVD) growth, (3) substrate-guided CVD, and (4) a soft-lock drawing method. We analyzed the underlying working principles, inherent advantages, and critical limitations of each approach. By benchmarking these methodologies against key performance metrics, this work aims to provide selection rules for the most suitable fabrication strategy for specific applications. Finally, we discuss remaining challenges and propose future opportunities, outlining the innovations required to propel aligned CNT-based technologies toward widespread applications.