Abstract
In the past, the research of ion beam sputtering (IBS) emphasized on how the incidence angle, ion energy and the flux of ion beam change the patterns formed on the sputtered substrates. The influence of metal impurities produced in the IBS process was usually ignored. In recent years, due to the metal co-deposition, the metal impurities has been evaluated as a key role in the formation of nano-patterns on the substrate surfaces. Therefore, it attracted the interest of many researchers. IBS has the advantage to carry out the deposition of metals of high-melting points which cannot be achieved easily by thermal evaporation in the past. In this research co-deposition of tantalum by IBS on the Si(111) surface to form tantalum silicides is our subject. The IBS conditions in our experiments are: a 2-keV Ar+ ion beam strikes the Si(111) surface at an incidence angle 30o to the surface normal. A tantalum sheet is positioned perpendicularly to the Si(111) substrate. When ISB is performed, both Ta sheet and Si(111) substrate are sputtered. The temperature of Si(111) substrate is kept at room temperature and 1000 K when IBS is carrying out. We observe the sputtered surface with STM at the distances of 0.9 mm, 1.2 mm, 1.5 mm, 1.8 mm and 2.1 mm from Ta sheet after sputtering followed by a post-annealing. Our goal is to investigate the structures and distributions of all possible surface features formed in the sputtering-annealing process. After post-annealing at 1293 K, we found two structures for 2D islands, both have metallic ehavior under STM imaging.The first one is √3×√3 structure with domains distributed on island surface.The second one is a honeycomb structure with interatomic separation 0.31 nm and covers the entire island surface without domain. So far we do not know its structure.In the experiment of IBS on hot Si(111) substrate at 1000 K, we found a semiconductor-like 2D island which has a √7×√7 structure.The 3D islands grow bigger irreversibly upon annealing. According to Si-Ta phase diagrams, the structure of 3D islands should be TaSi2. In our experiment, we try to find out the changes of 2D and 3D islands formed after the co-deposition of Ta on the Si(111) surface at different positions and Si substrate temperatures. We found three structures for 2D island and we conclude that the structure of 3D island is TaSi2. However, our conclusions of the structures for 2D islands are short of the reconfirmation of theoretical work. With the theoretical results, the structures of 2D islands can be determined correctly.