| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Ippei Yamamoto, Shibaura Institute of Technology, Japan |
| Authors: | I. Yamamoto, Shibaura Institute of Technology, Japan T. Kattareeya, Chulalongkorn University, Thailand T. Chikyo, NIMS, Japan K. Tsukagoshi, NIMS, Japan T. Ohishi, Shibaura Institute of Technology, Japan T. Nabatame, NIMS, Japan |
| Correspondent: | Click to Email |
The indium tin oxide (ITO), which is one of most attractive anode materials in organic electroluminescent, has a big issue of low work function (WF) of 4.7 eV. Several approaches have been proposed to improve the WF of ITO and/or develop new anode materials. We pay attention to RuO2 material because of high WF (> 5 eV) and low resistivity. In this paper, we systematically investigate the characteristics of the In1-xRuxOy films. We also compare characteristics of ITO/ultra-thin RuO2 (3 nm) and ITO/ultra-thin In1-xRuxOy (3 nm) stack structures.
The In1-xRuxOy films were prepared under Ar/O2 (25 vol. %) by co-sputtering using Ru and In2O3 targets. The Ru composition ratio of the In1-xRuxOy films was varied from 0 to 1.0 by changing each sputtering power. A 150-nm-thick ITO film was deposited on RuO2 (3 nm) or In1-xRuxOy (3 nm) film to fabricate ITO/RuO2 or ITO/In1-xRuxOy stack structure by RF sputtering using an In0.9Sn0.1Ox target, respectively. The SiO2 metal-oxide-semiconductor (MOS) capacitors with ITO/RuO2 or ITO/In1-xRuxOy gate electrode were fabricated to obtain effective work function (EWF).
The In1-xRuxOy film consists of amorphous structure in x range from 0.3 to 0.83. The In0.38Ru0.62Oy film shows a lowest specific resistivity and smooth surface of small RMS (0.69 nm) value using atomic force microscopy. The maximum transmittance increased more than 80 % by reducing thickness less than 3 nm.
The ITO/RuO2 (3 nm) stack structure shows a high EWF value (5.3 eV) and a slightly low transmittance (77 % in 600 nm) because the RuO2 film has tetragonal crystal structure. On the other hand, the transmittance (80 % in 600 nm) of ITO/In0.38Ru0.62Oy (3 nm) is superior to that of ITO/RuO2 stack structure. Furthermore, the ITO/In0.38Ru0.62Oy stack structure shows a high EWF (5.3 eV) and a low specific resistivity (9.2 ×10-5 Ω•cm). This suggests that the interface between ITO and In0.38Ru0.62Oy is kept to be clear because of same dominant element of indium and amorphous structure of In0.38Ru0.62Oy film.