DECOMPOSITION OF NH3 ON SI(100) - A SSIMS STUDY

The decomposition of NH3 on Si(100) has been studied using static secondary ion mass spectroscopy (SSIMS). Adsorption of NH3 on Si(100) at 100 K is dissociative and produces NH2(a) and H(a). Although slow thermal decomposition of NH2(a) to N(a) and H(a) occurs even at 320 K, most NH2(a) is stable up to 630 K. It decomposes rapidly between 630 and 730 K with an activation energy of 30 +/- 4 kcal/mol and a pre-exponential factor of 4 x 10(8 +/- 1) s-1. There is no evidence for NH(a). A small fraction of NH2(a) recombines with H(a) at 685 K, liberating NH3(g). H(a) desorbs as H-2 at 800 K and N(a) diffuses into the bulk of Si(100) above 750 K.