Nanostructured surfaces 

Properties of multilayer aluminum-doped indium saving ITO thin films deposited by sputtering method
Petrovska S.S.1, Sergiienko R.A.2, Ilkiv B.I.1, Nakamura T.3, Ohtsuka M.3
1Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhyzhanovski Str., 3, Kyiv-03142, Ukraine.
2 Physico-Technological Institute of Metals and Alloys, Vernadsky Ave., 34/1, Kyiv-03142, Ukraine.
3 Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
E-mail: makoto.ohtsuka.d7@tohoku.ac.jp

Multilayer (ML) aluminum-doped indium tin oxide (ITO) thin films with reduced to 50 mass% indium oxide content were prepared by co-sputtering of the ITO50 and Al2O3 targets in mixed argon-oxygen atmosphere onto very thin layer of conventional ITO (ITO90) deposited on glass substrates preheated at 523 K (ITO50:Al2O3/ITO90). Present work demonstrates the influence of the oxygen flow rate and heat treatment on optical, electrical, and structural properties of ML ITO50:Al2O3 thin films. It was found that as-deposited ML ITO50:Al2O3/ITO90 thin films sputtered in pure argon showed the decrease of the volume resistivity (445 µΩcm) in 1.6 times in comparison with single layer (SL) ITO50:Al2O3 thin films deposited at optimal conditions and in 6.3 times as compared with SL ITO50:Al2O3 thin films sputtered in pure argon atmosphere. Minimal volume resistivity in ML ITO50:Al2O3/ITO90 thin films can be achieved when depositing in pure argon atmosphere in contrast to undoped ML ITO50/ITO90, iron-doped ML ITO50:Fe2O3/ITO90 and ITO50:Fe3O4/ITO90 thin films, which need mixed argon-oxygen atmosphere to reach minimal values of volume resistivity. ML ITO50:Al2O3/ITO90 thin films deposited in pure argon atmosphere showed average transmittance larger than 85 % in the visible range. On the other hand, these films deposited in mixed argon-oxygen atmosphere showed average transmittance larger than 90 %. ML ITO50:Al2O3/ITO90 thin films showed polycrystalline In4Sn3O12 structure in as-deposited state and after heat treatment at 523 K. Peaks corresponding to aluminum oxide were not revealed on XRD patterns of ML ITO50:Al2O3/ITO90 thin films.