X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and high-resolution electron energy loss spectroscopy (HREELS) were used to study the adsorption and decomposition (for temperatures between 160 and 1100 K) of biacetyl(CH3COCOCH3)on Si(100). We conclude from peak positions in theC(1s)andO(1s)XPS spectra that biacetyl initially adsorbs by binding through the carbonyl π-bonds either forming a di-σ bonded form of biacetyl or completely cleaving the carbonyl double bond. In TPD, biacetyl molecularly desorbs at 185 K for the multilayer and between 263 and 285 K for the monolayer indicated in TPD. TPD also indicates ketene, methane, and hydrogen desorption at 330, 823, and 870 K, respectively. On the surface, there is evidence in XPS that all C=O containing fragments completely dissociate or desorb by 700 K. Above 700 K, hydrogen begins transferring to the surface as shown by the appearance of a peak in HREELS at2103 cm−1(νSi–H).Surface hydrogen recombines with methyl groups and other surface hydrogen producing methane (823 K) and molecular hydrogen (870 K). SiO desorbs at 1010 K and is reflected in XPS by total loss of theO(1s)signal. Finally, heating to 1100 K results in SiC formation.