The adsorption and thermal decomposition of dimethylamine on Si(100)

Dimethylamine [DMA; (CH3)2NH] adsorption on the Si(100)-(2×1) surface has been studied using Auger electron spectroscopy (AES), low-energy electron diffraction, and temperature-programmed reaction spectroscopy (TPRS). DMA appears to chemisorb with an initial surface saturation coverage of ∼0.5 ML at room temperature. These experiments also show evidence for continued room temperature adsorption of DMA for doses above this surface saturation dose level. TPRS data show that the decomposition of DMA adsorbed on the Si(100) surface proceeds via two radically different mechanisms in the low-dose vs. high-dose coverage regimes. The adsorbates directly bound to the surface in the low-dose regime are shown to decompose via reactions that form gaseous hydrogen (H2) and hydrogen cyanide (HCN) as major products, while the high-dose DMA species decompose to form H2 and imine dehydrogenation products. The imine appears to be the straight-chained N-methylmethanimine species (CH3NCH2). AES results show that repeated decomposition of DMA on Si(100) leads to the slow deposition of carbon- and nitrogen-based films, although the efficiency of thermal deposition is relatively low and the overall stoichiometry of the resulting amorphous films could not be clearly established.