Strain-Engineered Intramolecular Junctions in Chirality-Enriched Carbon Nanotubes with Gate-Tunable Photoresponse

Strain engineering serves as a pivotal method for modulating the electronic and optical properties of semiconductors, thereby realizing energy band engineering in low-dimensional materials. In this work, we report a strain-engineered photodetection architecture based on chirality-enriched single-walled carbon nanotubes (SWCNTs) that enables chirality-sensitive energy-band structure modulation, intramolecular junction (IMJ) formation, and gate-tunable spectral photoresponse. Height-tunable step structures are designed to introduce well-controlled uniaxial strain in SWCNT IMJ devices, allowing systematic correlation between mechanical deformation and optoelectronic behavior. Unlike conventional bulk materials or two-dimensional semiconductors, for which external strain typically induces a monotonic shift of their bandgaps, we find that devices based on SWCNT IMJs exhibit pronounced, chirality-dependent changes in photoresponse spectra under increasing uniaxial strain. The energy bandgaps extracted from spectra quantitatively follow the theoretically predicted strain-bandgap relationships with various trends for different chiral indices. Furthermore, electrostatic gating provides continuous tunability of both photocurrent amplitude and spectral response profile, showing active modulation of device photoresponse. These results demonstrate that strain-engineered IMJs in chirality-enriched SWCNT films can serve as a general method for energy band engineering and gate-tunable photoresponse, offering a practical route toward multifunctional and reconfigurable low-dimensional optoelectronic devices.