Effect of Ar plasma on the quality of atomic layer-by-layer Si epitaxial growth on Si(1 0 0) is investigated using the electron-cyclotron resonance (ECR) plasma enhanced chemical vapor deposition system. Adsorbed SiH4 molecules on monohydride Si(1 0 0) are effectively decomposed and form Si epitaxial film under the Ar plasma irradiation with the maximum and peak ion energies of 7 and 1-2 eV, respectively. As a result, atomic layer-by-layer control of Si epitaxial growth at a lower temperature below 100 degreesC is achieved by alternate exposure of Si(1 0 0) to SiH4 and Ar plasma. The plasma exposure also induces Ar incorporation in the film, and it is suggested that lowering the incorporated Ar amount below 2 x 10(21) cm(-3) is necessary to avoid degradation in crystallinity. (C) 2003 Elsevier B.V. All rights reserved.