Effects of carbon (C) atoms on solid-phase epitaxial growth of Ge on Si(100) have been studied. C and Ge layers were deposited on Si(100) substrates at low temperature (150-300 degrees C) by using solid-source molecular beam epitaxy (MBE) system and subsequently annealed at 650 degrees C in the MBE chamber. The surface morphology after annealing changed depending on deposited amounts of C and deposition temperature of Ge. Ge dots were formed for small amounts of C while smooth Ge films were formed by large amounts of C varying with the Ge deposition temperature. The surface morphology after annealing was also affected by the as-deposited Ge crystallinity. The change in surface morphology depending on the amounts of deposited C was considered to be affected by the formation of Ge-C bonds which relieved them is fit strain between Ge and Si. The crystallinity of Ge deteriorated with increasing C coverage due to the incorporation of insoluble C atoms in the shape of both dots and films. (C) 2015 Elsevier B.V. All rights reserved.