A first-principles study of 1D and 2D C60 nanostructures : strain effects on band alignments and carrier mobility.

In the breakthrough progress made in the latest experiment (Nature (2022) 606, 507), 2D C60 polymer was exfoliated from
the quasi-hexagonal bulk crystals. Bulk C60 polymer with quasi-tetragonal phase was found to easily form 1D fullerene
structure with C60 molecules connected by C--C. Inspired by the experiment, we investigate the strain behaviors of 1D
and 2D C60 polymers by first-principles calculations. Some physical properties of these low dimensional C60 polymers,
including structural stability, elastic behavior, band alignment and carrier mobility, are predicted. Compared with
fullerene C60 molecule, 1D and 2D C60 polymers are metastable. At absolute zero temperature, 1D C60 bears a uniaxial
tensile strain less than 11.5%, and 2D monolayer C60 withstands a biaxial tensile strain less than 7.5%. At 300 K,
ab initio molecular dynamics (AIMD) confirm that they can withstand the strains of 9% and 5%, respectively. Strain
engineering can adjust the absolute position of the band edge. In the absence of strain, carrier mobility is predicted to
be µe=398 and µh=322 cm2V-1s-1 for 1D C60 polymer, and µe,x = 74/µe,y=34 cm2V-1s-1 and µh,x = 646/µh,y=1487 cm2V-1s-1 for 2D C60 polymer. Compared with other carbon based semiconductors, these C60 polymers exhibit high effective mass, resulting in low mobility.