Investigation of post-annealing effect on Al:ZnO thin films crystallinity and photoluminescence properties

We investigated various structural, optical, and photoluminescence (PL) properties of as-deposited and postannealed Al:ZnO (AZO) thin films deposited by sputtering. X-Ray Diffraction (XRD) analysis indicated that a higher annealing temperature led to modifying the crystalline orientation from (002) to (110). Grain sizes of asdeposited AZO were as large as 12.8 nm, yet post-annealing increased them to 18.4 nm. Optical band gaps were determined to be in the range of 3.4-4 eV, which annealing caused noticeable decreasing in the band gaps. Postannealing could suppress the Urbach tail values from 0.573 to 0.276 eV. PL emission intensities improved more than 30 times as the result of suppressing the localized states. Both crystallinity and excitation wavelengths could play important roles on emission wavelengths; particularly if the value of excitation energy is close to that of the optical band gap. Fabricated AZO had suitable for light emitting diode (LED) and biological applications.

Automated summary

We investigated the effects of sputtering deposition and thermal annealing on the structural, optical, and photoluminescence properties of Al:ZnO (AZO) thin films. The results show that higher annealing temperature can modify the crystal orientation and grain size, as well as decrease the band gap. Post-annealing can suppress localized states and improve emission intensity, further enhancing the performance of the material.