Free-carrier compensation in ferromagnetic ion-implanted SnO2:Co

Abstract

Magnetron sputtered SnO2 thin films on fused silica substrates were doped with 3, 5, and 7at.% Co by the ion-implantation technique leading to ferromagnetic order at room temperature. Transmission electron microscopy combined with energy loss spectroscopy confirms the absence of Co clusters which are larger than the resolution of ∼1nm. Electrical transport measurements using the Van der Pauw method show a high resistivity of the undoped SnO2 which increases with the Co concentration. The lower valence of Co with respect to Sn causes a compensation of donor electrons by localized holes.