The growth of germanium films on Si(1 0 0) substrates prepared by two different methods is studied using atomic force microscopy and reflection high energy electron diffraction. The first method uses a brief Ar+ sputter followed by annealing to desorb the remaining oxide, resulting in a Rat substrate. The second method involves the pre-treatment of the sample with an oxygen plasma discharge before annealing. Pre-treating the Si(1 0 0) surface with an oxygen plasma discharge can sometimes result in etch pits that dramatically affect the growth of the germanium film. The diffusion length of germanium on the pretreated sample at 750 K is estimated to be greater than or equal to 700 +/- 100 nm by measuring the size of island-free terraces surrounded by etch pits.