Silicon-germanium and platinum silicide nanostructures for silicon based photonics

This paper reports a study of two types of silicon based nanostructures prospective for applications in photonics. The first ones are Ge /Si(001) structures forming at room temperature and reconstructing after annealing at 600 degrees C. Germanium, being deposited from a molecular beam at room temperature on the Si(001) surface, forms a thin granular film composed of Ge particles with sizes of a few nanometers. A characteristic feature of these films is that they demonstrate signs of the 2 x 1 structure in their RHEED patterns. After short-term annealing at 600 degrees C under the closed system conditions, the granular films reconstruct to heterostructures consisting of a Ge wetting layer and oval clusters of Ge. A mixed type c(4 x 2) + p(2 x 2) reconstruction typical to the low-temperature MBE (T-gr < 600 degrees C) forms on the wetting layer. Long-term annealing of granular films at the same conditions results in formation of c(4 x 2)-reconstructed wetting layer typical to high-temperature MBE (T-gr > 600 degrees C) and huge clusters of Ge. The other type of the studied nanostructures is based on Pt silicides. This class of materials is one of the friendliest to silicon technology. But as silicide film thickness reaches a few nanometers, low resistivity becomes of primary importance. Pt3Si has the lowest sheet resistance among the Pt silicides. However, the development of a process of thin Pt3Si films formation is a challenging task. This paper describes formation of a thin Pt3Si /Pt2Si structures at room temperature on poly-Si films. Special attention is paid upon formation of poly-Si and amorphous Si films on Si3N4 substrates at low temperatures.