TiO2 as diffusion barrier at Co/Alq3 interface studied by x-ray standing wave technique

Nano-scale diffusion at the interfaces in organic spin valve thin films plays a vital role in controlling the performance of magneto-electronic devices. In the present work, it is shown that a thin layer of titanium dioxide at the interface of Co/Alq(3) can act as a good diffusion barrier. The buried interfaces of Co/Alq(3)/Co organic spin valve thin film has been studied using x-ray standing waves technique. A planar waveguide is formed with Alq(3) layer forming the cavity and Co layers as the walls of the waveguide. Precise information about diffusion of Co into Alq(3) is obtained through excitation of the waveguide modes. It is found that the top Co layer diffuses deep into the Alq(3) resulting in incorporation of 3.1% Co in the Alq(3) layer. Insertion of a 1.7 nm thick barrier layer of TiO2 at Co/Alq(3) interface results in a drastic reduction in the diffusion of Co into Alq(3) to a value of only 0.4%. This suggests a better performance of organic spin valve with diffusion barrier of TiO2.