Nanostructural and barrier property characterization of ZnO/PEDOT:PSS heterojunction by adjusting RF power in the magnetron sputtering deposition technique

Abstract

Nanostructure and barrier properties of the heterojunction formed at the interface of ZnO/PEDOT:PSS inorganic/organic contact have been investigated. The PEDOT:PSS layer and the zinc oxide nanostructures have been deposited using the spin coating and the radio frequency magnetron sputtering techniques on glass substrates at room temperature, respectively. Particularly, the effects of zinc oxide sputtering power on the nanostructure properties of the deposited layer are investigated. The deposition power varies from 60 to 240 W. AFM results show that increasing the deposition power, results in the grain size and the surface roughness of the zinc oxide layer to increase. The energy gap measured for the zinc oxide layers deposited at the powers of 60, 120, 180 and 240 W was 3.24, 3.23, 3.18, and 3.20 eV, respectively. In order to investigate the heterojunction formed at the interface of zinc oxide and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS), a polymeric layer of thickness of 50 nm is deposited on a 300-nm zinc oxide layer. The dark I–V characteristics indicate that the reverse saturation current density is 5.01 × 10⁻⁷, 3.16 × 10⁻⁵, 1.96 × 10⁻⁷ and 7.98 × 10⁻⁷ A/cm² for the deposition power of 60, 120, 180, and 240 W, respectively. By increasing the deposition power the ideality factor of the resulting Schottky barrier is 3.2, 2.9, 2.3 and 3.6. The effective Schottky barrier heights of 0.76, 0.77, 0.78, and 0.75 eV were obtained for the same order of deposition powers. It was found that the highest optical response could be obtained for the samples prepared at the deposition power of 180 W.