The adsorption and decomposition kinetics of diethylsilane (DES), (CH3CH2)2SiH2, on silicon surfaces were studied using laser‐induced thermal desorption (LITD), temperature programmed desorption, and Fourier transform infrared (FTIR) spectroscopic techniques. LITD measurements determined that the initial reactive sticking coefficient of DES on Si(111) 7×7 decreased versus surface temperature from S0≊1.7×10−3at 200 K to S0≊4×10−5at 440 K. The temperature‐dependent sticking coefficients suggested a precursor‐mediated adsorption mechanism. FTIR studies on high surface area porous silicon surfaces indicated that DES adsorbs dissociatively at 300 K and produces SiH and SiC2H5surface species. Annealing studies also revealed that the hydrogen coverage on porous silicon increased as the SiC2H5surface species decomposed. CH2=CH2and H2were the observed desorption products at 700 and 810 K, respectively, following DES adsorption on Si(111) 7×7. The ethylene desorption and growth of hydrogen coverage during ethyl group decomposition were consistent with a β‐hydride elimination mechanism for the SiC2H5surface species, i.e., SiC2H5→SiH+CH2=CH2. Isothermal LITD studies monitored the decomposition kinetics of SiC2H5on Si(111) 7×7 as a function of time following DES exposures. The first‐order decomposition kinetics wereEd=36 kcal/mol and νd=2.7×109s−1. These decomposition kinetics suggest that the silicon surface catalyzes the β‐hydride elimination reaction.