Atomic layer deposition of iron oxide thin films and nanotubes using ferrocene and oxygen as precursors

Thin films and nanotubes of iron oxide are deposited using atomic layer deposition (ALD) on Si(100) and anodic aluminum oxide (AAO), respectively. Ferrocene, Fe(Cp)(2), and oxygen are used as precursors. Successful depositions are carried out in the temperature range 350-500 degrees C on Si(100), while all depositions on AAO are made at 400 degrees C. The growth per cycle values are around 0.14 nm on Si(100) in the temperature range 350-500 degrees C and 0.06 nm on AAO. Below 500 degrees C, the iron oxide crystallizes as a phase mixture on both types of substrates. One of the phases is identified as the rhombohedral Fe2O3 phase (hematite), but the second phase cannot be unambiguously identified. Above 500 degrees C, only phase pure hematite is detected. For deposition of nanotubes, in-house made AAO membranes are used, having an aspect ratio of 30. By etching of the AAO membranes after deposition, free-standing nanotubes retaining the order of the AAO template can be fabricated.