Doping-driven structural and electronic modulation in Tripentaphene Nanocarbon allotrope

Abstract

Tripentaphenes (TPHs) are two-dimensional carbon allotropes composed of periodically arranged acepentalene units. Using density functional theory, we examine boron- and nitrogen-doped TPHs, revealing that substitutional doping slightly modifies lattice parameters—boron expanding and nitrogen contracting—while preserving energetic stability. Electronic behavior depends on structural configuration: $\alpha$- and $\sigma$-TPHs remain metallic or semimetallic, whereas $\beta$-TPHs exhibit tunable semiconducting gaps. Effective mass analysis for gapped systems shows pronounced anisotropy, with $\beta$-/$\sigma$-co-doped systems displaying large off-diagonal tensor elements, indicating direction-dependent transport and mobility. Raman spectra of semiconducting $\beta$-TPHs reveal dopant-specific fingerprints: boron doping induces red-shifted $G$-like modes, nitrogen introduces dopant-induced symmetry-breaking breathing-like vibrations analogous to the $D$ band, and co-doping generates complex mixed modes, including high-frequency modes. These results highlight $\beta$-TPHs as promising anisotropic semiconductors for 2D electronics and optoelectronics, with metallic $\alpha$- and $\sigma$-phases serving as potential contact layers.