Nanostructure wrinkle thin films on flexible substrate: Tunable optical properties

Abstract

Nanostructure wrinkle created by amorphous diamond like carbon (a:DLC) thin films on a flexible Polyethylene Terephthalate (PET) substrate via chemical bath deposition technique was studied in detail. Atomic force microscopy (AFM) image revealed that the nanostructure wrinkle pattern with varying wavelengths from 350 nm to 170 nm are closely spaced and randomly oriented on the PET substrate. Raman spectra analysis showed that the chemical composition i.e., sp2/(sp2 + sp3) bonding ratio in the deposited a:DLC nanostructure wrinkle thin films was varied by changing the sucrose weight percentage in the precursor solution used for a:DLC thin film deposition. The optical band gap energy decreased from 3.17 eV to 2.04 eV for the a:DLC nanostructure wrinkle thin films due to increasethe sucrose weight percentage in the precursor solution from 5 to 30 respectively. The disorderness and defect density in the a:DLC nanostructure wrinkle thin films calculated from Raman spectra as well as from Urbach energy calculation. The change in optical transmittance, extinction coefficient, refractive index and optical band gap energy has been discussed in terms of composition and nanostructure wrinkle pattern of the a:DLC thin films.