A study of deposition of ITO films on organic layer using facing target sputtering in Ar and Kr gases

In this study, the effects of sputtering gases on the damage to an organic layer (aluminum (III) bis(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq)) were investigated in the deposition of indium–tin oxide (ITO) films by using a facing target sputtering (FTS) system. Only a small improvement in the PL intensity of the BAlq layer was observed when the sputtering gas was changed from Ar to Kr gas. It was also found that suppression of the high-energy γ-electron bombardment to the substrate is very important to reduce the damages in the BAlq layers. In addition, a remarkable improvement in the PL intensity was observed by the increase in the sputtering gas pressure from 0.3 to 1.3 Pa. These results suggest that bombardment of reflected neutral gas atoms is not the main source of the damage that BAlq layer has, but the bombardment of high-energy sputtered atoms plays an important role for the remnant damages caused by the sputter-deposition of the ITO film at a low gas pressure, since the decrease in the PL intensity was almost totally suppressed by increasing the sputtering gas pressure above 1.1 Pa. Finally, low-damage sputter-deposition of ITO film with low resistivity on BAlq layer was achieved by completely suppressing the bombardment of high-energy particles, including γ-electrons, negative oxygen ions and high-energy sputter-emitted particles.