Effects of Hydrogen on the Optical and Electrical Characteristics of the Sputter-Deposited Al2O3-Doped ZnO Thin Films

In this study, AZO thin films were deposited on glass by using a 98 mol% ZnO + 1mol% Al2O3 (AZO, Zn : Al = 98 : 2) ceramic target and ar.f. magnetron sputtering system. At first, the effects of different H-2 flow rates (H-2/(H-2 + Ar) = 0%similar to 9.09%, abbreviated as H-2-deposited AZO thin films, deposition temperature was 200 degrees C) added during the deposition process on the physical and electrical properties of AZO thin films were investigated. The optical transmittance at 400nm similar to 700nm is more than 80% for all AZO thin films regardless of H-2 flow rate and the transparency ratio decreased as the H-2 flow rate increased. The Burstein-Moss shift effect was used to prove that the defects of AZO thin films decreased with increasing H-2 flow rate. Also, the 2% H-2-deposited AZO thin films were also treated by the H-2 plasma at room temperature for 60 min (plasma-treated AZO thin films). The value variations in the optical band gap (E-g) values of the H-2-deposited and plasma-treated AZO thin films were evaluated from the plots of (alpha hv)(2) = c(hv - E-g), and the E-g values increased with increasing H-2 flow rate. The E-g values also increased as the H-2-plasma process was used to treat on the H-2-deposited Al2O3-doped ZnO (AZO) thin films.