Growth of the single and epitaxial MgO film on Fe(001)

The epitaxial growth of MgO film on Fe(001) has been investigated by scanning tunneling microscopy (STM). After confirming the clean Fe(001)-c($2{\times}2$) substrate by STM, Mg was deposited at room temperature (RT) under $O_2$ partial pressure of $10^{-7}\;Torr$. The MgO was grown as clusters, not as an epilayer even after postannealing at $400^{\circ}C$, as shown in Figure (a). On the contrary, when Mg was deposited on Fe(001)-c($2{\times}2$) at RT and post-oxidized through exposing $O_2$ at partial pressure $10^{-7}\;Torr$, the thin-layered film with some clusters was formed. Extended-annealing at $400^{\circ}C$ reduced the cluster density, and finally the single and epitaxial MgO-c($2{\times}2$) film was formed on Fe(001)-c($2{\times}2$) as shown in Figure (b). This ultrathin MgO film formed on Fe is expected to be applied to many technological applications, such as catalysis, microelectronics, and magnetic devices.