Carbon nanotubes: From disordered ensembles to van der Waals crystals.

Carbon nanotubes (CNTs) have ignited worldwide excitement for their extraordinary electrical and mechanical properties. Yet, despite decades of effort, realizing the "dream material" for carbon-based electronics-a wafer-scale, perfectly aligned, single-chirality, densely packed array of semiconducting CNTs-has remained elusive. Here, we provide a perspective on the recent breakthroughs that are bringing this vision closer to reality. We highlight advances in both chemical vapor deposition (CVD) and post-growth assembly, culminating in the emergence of van der Waals (vdW) crystals of single-chirality CNTs self-assembled on atomically flat hexagonal boron nitride (hBN) surfaces. We discuss the fundamental mechanisms, device implications, and rich opportunities for interdisciplinary exploration in quantum physics, materials science, and electronics.