Unpredicted surface termination of alpha-Fe2O3(0001) film grown by mist chemical vapor deposition

作者：Osaka Shun; Kubo Osamu; Takahashi Kazuki; Oda Masaya; Kaneko Kentaro; Tabata Hiroshi; Fujita Shizuo; Katayama Mitsuhiro

来源：Surface Science, 2017, 660: 9-15.

DOI：10.1016/j.susc.2017.02.002

• Coaxial impact-collision ion scattering spectroscopy
• Iron oxide
• Mist chemical vapor deposition
• Surface termination

We analyze the surface structure of an alpha-Fe2O3(0001) film grown on a c-plane sapphire substrate by mist chemical vapor deposition (CVD), which has been recently developed as a simple, safe, and cost-effective film growth method. Using coaxial impact-collision ion scattering spectroscopy, we found that the atomic-layer sequence of the surface termination of an alpha-Fe2O3(0001) film grown by mist CVD was Fe-O-3-Fe- from the top layer. This surface termination is predicted to form in an oxygen-poor environment by density functional theory combined with a thermodynamical approach despite that the mist CVD process is performed with atmospheric pressure air. The surface structure markedly changes after annealing above 600 degrees C in ultrahigh vacuum. We found that only a couple of layers from the top layer transform into Fe3O4(111) after 650 degrees C annealing, which would be so-called biphase reconstruction. Complete transformation into a Fe3O4(111) film occurs at 700 degrees C, whose atomic-layer sequence is determined to be Fe-O-4-Fe-3- from the top layer.

• 出版日期2017-6