The fabrication process of high-quality freestanding diamond films grown by Microwave Plasma Chemical Vapor Deposition (MPCVD) was studied. Under the optimal condition, freestanding diamond films 55 mm in diameter with a thickness up to 1 mm were fabricated, showing an excellent crystalline structure as examined from Raman and X-Ray Diffraction (XRD) spectra. For most processing conditions, including substrate temperatures varied from 800 to 1050 degrees C, the films were found in a [1 1 1] preferential texture, whereas [2 2 0] and [0 0 1] film textures occurred in some special cases. Optical measurements of one side polished diamond films showed a cutoff wavelength 225 nm, and a transmission >= 70% at lambda >= 2.5 mu m. (C) 2012 Elsevier B.V. All rights reserved.