Tuning the electronic and optical properties of monatomic carbon chains

The electronic, mechanical and optical properties of the monatomic carbon chains recently fabricated are investigated by hybrid density functional calculations. It is shown that the chain owns a direct band gap of 2.21 eV and the ultimate strength of 12.2 nN, which are in good agreements with experiments. The light absorption shows only one sharp peak in a wide photonic energy range up to 10 eV and exhibits a strong anisotropic feature as the absorption of the visible light polarized along the chain axis is five orders of magnitude stronger than that of the light polarized perpendicularly to the chain. By applying elastic strains on the chain, the band gap can be continuously changed from 1.58 to 3.86 eV with the absorption peak shifting correspondingly. Then a realistic graphene-chain device is proposed and is verified to be capable of applying strains up to 9% on the chain, suggesting potential applications in nano-size electro-optical and polarization devices with tunable working wavelengths from 345 to 561 nm.