Filament‐assisted chemical vapor deposition (CVD) diamond film growth on Si(100) was studied using x‐ray photoelectron spectroscopy (XPS) to examine the sample at selected intervals during the nucleation and growth processes. The sample was transferred under vacuum from the growth chamber to the attached XPS analysis chamber without exposure to air. Before growth XPS showed that the Si sample is covered by a layer of SiO2and carbonaceous residue; however, after 15 min of growth both of these substances are removed and replaced by a distinct SiC layer [Si(2p)=100.3 eV andC(1s)=282.7 eV].