The structure of alkylsiloxane self-assembled monolayers formed on HF-treated Si3N4 has been studied using x-ray photoelectron spectroscopy, high-resolution electron energy-loss spectroscopy, and contact angle analysis. It is shown that the monolayers are similar in quality to those formed on oxidized silicon, despite the fact that upon etching in HF, the Si3N4 surface contains only 0.2 ML of oxygen. In contrast, on NH4F-treated Si(100) surfaces with similar quantities of oxygen, high-quality monolayers cannot be formed. We argue that these results point to the importance of a water layer in monolayer formation.