The initial oxidation process of thin aluminum films used in ferromagnetic tunnel junctions was investigated by scanning tunneling microscopy (STM). The STM images reveal the progression of oxygen penetration into an aluminum film composed of small grains. The oxygen first covers the aluminum grain surface homogeneously. At the same time, the oxygen is inserted into the aluminum grain boundaries. As the oxidation proceeds, the oxygen penetrates inside the grain.
- Ferromagnetic tunnel junction
- Local transport
- Radical oxidation