Thin Films of Cobalt Oxide Deposited on High Aspect Ratio Supports by Atomic Layer Deposition

Thin films of cobalt oxide are obtained by atomic layer deposition (ALD) using cobaltocene (CoCp2) and ozone as precursors. A window for ALD growth exists in the temperature range 137 to 331 degrees C. Self-limiting growth is verified at a deposition temperature of 167 degrees C. X-ray diffraction (XRD) analysis indicates that the films consist of polycrystalline Co3O4 up to a deposition temperature of some 285 degrees C with CoO being identified as a secondary phase at 331 degrees C. Atomic force microscopy (AFM) proves increased roughness and grain size with increasing deposition temperature, apart from films deposited at 235 degrees C where the roughness is very low due to a change in preferred orientation of the growth. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping measurements on coated anodiscs show a homogeneous deposition of cobalt oxide on the 5 mu m upper part of the pores structure. The content of cobalt decreases inside the pores, however, still proving the existence of cobalt inside all pores.