Jianshu Yang

Surface structures of silicon nitride thin films on Si(111)

Abstract After exposing Si(111) to NH 3 at about 1075 K, a 10.2-A surface periodic structure (the ‘8/3×8/3’ reconstruction) is observed in scanning tunneling microscopy images. When the nitridation temperature is above 1125 K, a silicon nitride film with a surface superstructure with a period of 30.7 A and a minimum step height of 2.9 A is obtained. Our systematic analyses suggest that the 30.7-A superstructure is the 4×4 reconstruction on the Si 3 N 4 (0001) surface of the crystalline silicon nitride ( β -Si 3 N 4 ) thin film formed on Si(111), while the 10.2-A periodic structure is an incomplete nitridation phase on Si(111) surface. The surface structure has been found to be sensitive to the impurities in NH 3 .

Self-assembled growth of cubic silicon carbide nano-islands on silicon

Silicon carbide(SiC) nano-crystallites are formed by the thermal reaction of C60 molecules with silicon atoms on Si(0 0 1) and Si(1 1 1) surfaces at 900–11508C. The surface morphologies and structures of the cubic b-SiC islands on Si(0 0 1) and Si(1 1 1) are investigated in situ using scanning tunneling microscopy. Comparing to bulk SiC crystals, distinctive atomic structures are formed on the surfaces of the SiC crystallites: a (2 � 3) on SiC(0 0 1) and a ð2 ffiffiffi 3 p �

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≈1175 K. The crystallinity of the film on Si(111) has been verified with high-resolution cross-sectional transmission electron microscopy (TEM) and scanning tunneling microscopy. The thickness of the SiNx film is 3–6 atomic layers. When compared with the known phases of Si3N4, our SiNx film is relatively close to β-Si3N4, but it could be a new phase of silicon nitride. Si or Ge forms 3D islands initially when deposited on both crystalline and amorphous SiNx films, and most of the islands are not aligned with the 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 films remain polycrystalline in later stages of growth.