Diamond films are prepared by microwave plasma-enhanced chemical-vapor deposition on Si (100) substrates using the H-2-Ar-CH4 gases. Raman scattering data, including the peak position, intensity, area, and width, are analyzed in depth and used to obtain the sp(3)- and sp(2)-bonded carbon contents and the nature of internal stresses in the films. Polarization behavior of the Raman peaks is analyzed to assess its role on the quantitative analysis of the diamond films, which suggested that the 1150 cm(-1) Raman peak in nanocrystalline diamond films could be attributed to sp(2)-bonded carbon. The role of the H-2/Ar content in the gas mixture and substrate temperature on the characteristics of the diamond film is studied. Thickness and grain size of diamond films are also determined by scanning electron microscopy and related to the deposition conditions and Raman results. Deposition conditions, which led to highest sp(3)-bonded carbon content and growth rate, are identified. (c) 2006 American Vacuum Society.