The decomposition of ammonia on Si(111) 7×7 was studied using laser‐induced thermal desorption (LITD), temperature‐programmed desorption (TPD), and Auger electron spectroscopy (AES). Product yields versus NH3exposure were determined using TPD and LITD measurements. Besides the NH3multilayer desorption, the only TPD products were H2and Si2N, which desorbed at ∼800 and 1350 K, respectively. H2was also observed in the LITD yield from NH3on Si(111) 7×7. In addition, NH3, SiNH2, and SiNH were detected in the LITD yield at temperatures above the NH3multilayer desorption. After saturation NH3exposures, the LITD desorption yield for NH3and SiNH2persisted until 700 K, and the SiNH LITD signals were observed up to 800 K. These SiNH2and SiNH LITD signals were assigned to reaction intermediates on the Si(111) 7×7 surface because neither SiNH2nor SiNH was observed in the TPD yield. The effect of preadsorbed deuterium on the reactive adsorption of NH3was also investigated. Deuterium was observed to decrease the product yield from NH3decomposition on Si(111) 7×7.