Diamondlike amorphous C films with exceptionally low stress (<108 dyn/cm2) have been prepared by a hybrid process involving bias sputtering with ultrapure C electrodes and plasma decomposition of normal butane. The low stress is believed to be related to the H2 content of the films (<1 at.%). The films have a high density (2.8 g/cm3) and are resistant to wear and abrasion. The films are good dielectrics (ε′=8.8; Q=130; ζ=1.5×1014 Ω ⋅ cm; Ed=3.5×107 V/cm). They are transparent in the visible spectrum and have properties in the infrared that lend themselves to the production of good antireflection coatings. The band gap of the films is about 3.0 eV.