Nanostructured surface 

Aluminum-doped indium saving indium-tin oxide thin films sputtered on preheated substrates 
Petrovska S.S.1, Sergiienko R.A.2, Ilkiv B.I.1, Nakamura T.3, Ohtsuka M.3
1 Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine. Krzhyzhanovski Str., 3, Kyiv-03142, Ukraine.
2Physico-Technological Institute of Metals and Alloys, Vernadsky Ave., 34/1,  Kyiv-03142, Ukraine. 
3Institute 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

The aluminum-doped indium tin oxide (ITO) thin films with reduced to 50 mass% indium oxide content were prepared by co-sputtering of the ITO and Al2O3 targets in mixed argon-oxygen atmosphere onto glass substrates preheated at 523 K (ITO50:Al2O3 (PHS)). Present work demonstrates the influence of the RF powers of Al2O3 target and heat treatment on optical, electrical, and structural properties of ITO50:Al2O3 (PHS) thin films.
It was found that the transmittance of the ITO50:Al2O3 (PHS) thin films was improved significantly at fixed oxygen flow rate Q(O2)=0.1 sccm when a high radio frequency power increased. It was observed since aluminum oxide is an additional source of oxygen during filling of oxygen vacancies. 
It was shown that optimum radio frequency power was WRF (Al2O3)=40 W. The volume resistivity of the as-deposited ITO50:Al2O3 (PHS) thin films sputtered under such conditions was 713 µΩ cm. Further increase of WRF (Al2O3) conduces to increase of volume resistivity. This may be connected with dying out of doping effect of aluminum oxide. 
Introducing of Al2O3 to the ITO50 thin films did not alter the ITO structure.
The effect of sputtering with Ar+ ions on the surface electronic structure of ITO thin films was investigated using XPS measurements. Ar+ sputtering efficiently removed surface contaminations.
In is in In3+ bonding state, Sn is in Sn3+ bonding state and Al is in Al3+ bonding state for both films before and after Ar+ sputtering.