Growth, physical and electrical characterization of nickel oxide thin films prepared by plasma-enhanced atomic layer deposition using nickelocene and oxygen precursors

Abstract

Nickel oxide (NiO) thin films are prepared by plasma-enhanced atomic layer deposition using nickelocene (NiCp _2 ) and oxygen (O _2 ) precursors. The effects of process parameters on the growth rate of NiO film are investigated, including deposition temperature, NiCp _2 pulse time, and O _2 plasma pulse time. In terms of deposition temperatures between 225 and 275 °C, a stable growth rate of ∼0.17 Å/cycle is obtained, meanwhile, the deposited films contain Ni(II)−O, Ni(III)−O, Ni(II)−OH, C−C bonds and metallic Ni atoms, and exhibit a smooth surface with root-mean-square roughness of ≤0.37 nm. As the deposition temperature increases from 150 to 350 °C, the deposited NiO film changes from an amorphous state to a NiO (200) orientation-dominated texture and further to NiO (111) and (200) orientations concomitant polycrystalline one; at the same time, the transmittance of the film shows a decline tendency, and the optical band gap decreases from 3.69 to 3.48 eV. Furthermore, it is found that the deposited NiO film behaves like a dielectric rather than a semiconductor, and for the NiO film deposited at 250 °C, a dielectric constant of 16.7 is demonstrated together with a film composition of 51.6% Ni, 40% O and 8.4% C.

Keywords

• atomic layer deposition
• nickel oxide
• nano-films