Tailoring the morphology, optical and electrical properties of DC-sputtered ZnO:Al films by post thermal and plasma treatments

Abstract Post thermal and plasma treatments are used to improve the morphology, optical and electrical properties of ZnO:Al (AZO) films prepared by DC-sputtering at room temperature. H-plasma treated sample exhibits the biggest surface roughness (Root Mean Square, RMS) of 6 nm in all the samples. All the films show high transmittance above 90% in 400–800 nm visible range. The ∼0.20 eV blue-shift of the band gap is observed both in H 2 annealed and H-plasma treated samples due to the defect and grain boundary passivation by hydrogen introduction. The improvement of the electrical properties is obvious except for 500 °C O 2 annealed sample ( ρ =8.96×10 −2 Ω cm, μ =5.50 cm 2 V −1 S −1 , and n =1.26×10 19 cm −3 ) because of the extra oxygen substitution for vacancy oxygen (V o ) and the formation of oxides. The lowest resistivity (2.94×10 −3 Ω cm) and highest mobility (12.00 cm 2 V −1 S −1 ) are obtained after H-plasma treatment. The significant increment of the carrier concentration indicates that hydrogen atoms have been injected to the lattice during H-plasma processing. Such good textured surface morphology and transparent conductive properties suggest that AZO films have potential possibilities in thin film silicon (TFS) solar cell for light trapping.