Characterization of silicon nitride thin films on Si and overlayer growth of Si and Ge

Crystalline silicon nitride (SiNx) thin films on Si(111) and amorphous SiNx films on Si(001) have been obtained after NH3 or NO exposure at T approxim ate to 1175 K. The crystallinity of the film on Si(III) has been verified w ith high-resolution cross-sectional transmission electron microscopy (TEM) and scanning tunneling microscopy. The thickness of the SiNx film is 3-6 at omic layers. When compared with the known phases of Si3N4, our SiNx film is relatively close to beta -Si3N4, but it could be a new phase of silicon ni tride. Si or Ge forms 3D islands initially when deposited on both crystalli ne and amorphous SiNx films, and most of the islands are not aligned with t he Si substrates. However, on SiNx/Si(111), the islands aligned with the Si substrate grow faster than other islands, so that the overlayer gradually grows into a (111)-oriented columnar film. On SiNx/Si(001), the overlayer f ilms remain polycrystalline in later stages of growth.