Oxygen effect in radio frequency magnetron sputtered aluminium doped zinc oxide films

• Transparent and conductive ZnO:Al films were deposited using magnetron sputtering.
• The influence of plasma oxygen content was investigated.
• Film preferential orientation depends on substrate nature.
• Film stress is compressive, it decreases with reducing oxygen content.

In the present work, polycrystalline transparent conductive aluminium doped zinc oxide (ZnO:Al) films, have been grown on glass and silicon substrates by radio frequency magnetron sputtering technique at room temperature. The effect of oxygen content in the fed gas, on the structural, optical and electrical film properties was investigated. We found that film growth rate decreases with increasing oxygen content. The crystalline of ZnO:Al films deposited on glass substrates has an hexagonal structure with a preferential orientation along the c-axis. While for films deposited on silicon substrates, the crystallites preferred orientation shifts gradually from (002) to (100) direction as the oxygen content increases. While near stress-free film was obtained at 0% O2 content, intrinsic stress also increases with the oxygen content. Low resistivity (ρ = 1.25 × 10− 3 Ω cm) associated with high transmittance (T > 92%) in the visible regions was measured in ZnO:Al film deposited at room temperature with no oxygen in the deposition chamber. The optical characterization indicated that the band gap shifts towards lower energies with increasing oxygen content.