Plasma characteristics of 355 nm and 532 nm laser deposition of Al-doped ZnO films

• Zn, Al and O species were obtained in 355 nm and 532 nm laser ablation of AZO.
• Kinetic energy of the ions was 15–230 eV depending on the laser fluence.
• 355 nm laser produced ionized species for high quality nanostructured AZO films.
• Ablation by 532 nm laser produced particulates because of a high penetration depth.
• The large particulates in 532 nm ablation were Al rich.

The plasma characteristics of 355 nm and 532 nm laser ablation of Al-doped ZnO (AZO) target were studied by optical emission spectroscopy and ion probe measurements. Zn emission lines were measured detected at above 0.9 J/cm2 for 355 nm laser and 0.6 J/cm2 532 nm laser respectively, while Al species were detected only above 2 J/cm2. The kinetic energy of the ions was slightly higher for 532 nm ablation as compared to 355 nm ablation. In addition, the ablation of 532 nm laser was affected by the large laser penetration depth. When deposited at 2 and 4 J/cm2, AZO films with energy band gap of 3.45–3.6 eV were obtained. Nanostructured AZO films were obtained by 355 nm laser ablation but nano and micro-particulates were formed in 532 nm laser ablation. The large micron-sized particulates were Al-rich thus affecting not only the morphology but also the stoichiometry of the films. It is thus concluded that despite a lower ablation and growth rate, 355 nm generated Zn, O and also Al species at lower threshold fluence that can lead to high quality AZO films at room temperature.