Controlled thinning of aligned single-wall carbon nanotube films by multiple exfoliation

Abstract

Achieving macroscopic alignment of single-wall carbon nanotubes (SWCNTs) is pivotal for unlocking their full potential in high-performance optoelectronic devices, nonlinear optical platforms, and chiral quantum systems. Among various fabrication techniques, the controlled vacuum filtration (CVF) method offers a scalable route to dense, aligned SWCNT films. However, it suffers from a persistent drawback: the accumulation of disoriented layers near the film surface, especially in thick or chirality enriched samples, which severely compromises optical anisotropy and electronic transport. Here, we introduce a multiple exfoliation technique that selectively removes these disoriented layers while preserving the structurally ordered bottom region. This process significantly enhances the degree of alignment, as evidenced by a more than twofold increase in Raman anisotropy and a fivefold improvement in electrical transport anisotropy. Crucially, this method is universal, regardless of film thickness or nanotube species, enabling precise structural refinement after deposition. By transforming partially aligned CVF films into ultra-aligned architectures, our approach establishes a paradigm for deterministic structural engineering of SWCNT materials. This advancement paves the way for the scalable production of highly ordered SWCNT systems, which are essential for polarized light emitters, spin-selective filters, and secure quantum communication devices.