It is known from previous work [R. W. Springer and D. S. Catlett, J. Vac. Sci. Technol. 15, 210 (1978)] that the residual gases can play a significant role in determining the resultant chemical purity of vacuum-deposited films. The ability to alter the chemical composition and structure of a solid on a microdimensional scale can provide a means to tailor and control the mechanical properties of the material [see R. W. Springer and D. S. Catlett, Thin Solid Films 54, 197 (1978)]. Acetylene gas was admitted to the chamber over approximately two orders of magnitude of pressure during Ta deposition. Residual gas analysis was used to verify that a reaction between the Ta film and the gas occurred. Subsequent Auger analysis showed that the carbon in the films could be predicted using a simple pressure-versus-rate equation. The pulsed gas process (PGP) has been applied to the electron beam gun deposition of Ta. Tensile test specimens a few μm thick have been produced show fracture strengths varying from ∠ 170 to ∠860 mPa for pure to highly pulsed runs. The fracture strength loosely follows a Hall–Petch relation relating fracture strength to the time between pulses. Although diffusion of the carbon smoothes out the chemical period, it is thought that the remaining structure accounts for the strength enhancement.