Our interests in growing thin films of iron (Fe) are twofold. First, Fe(001) films are ideal targets for an ultrafast x-ray diffraction instrument designed to understand complex behavior, such as melting or solid-solid phase transitions, in shock-loaded materials. Second, we have discovered that thin iron films generate picosecond, broadband terahertz frequencies after intense femtosecond pulse excitation by a Ti:sapphire laser. Excluding film thickness, the criteria for samples used in both experiments are identical due to the similarities of the experiments. Iron films are grown in ultrahigh vacuum (UHV) conditions on (001)-oriented magnesium oxide (MgO) substrates. We have investigated the effects of substrate preparation on the film quality and have found that films grown in UHV on UV/ozone-cleaned and annealed MgO(001) have a better crystal quality than films grown on as-received MgO(001). However, both substrate preparation methods produce continuous, (001)-oriented thin films of iron. © 2006 American Vacuum Society.