Growth of metal nanostructures on silicon surfaces is very important both for scientific and technological reasons. However, single metal nanostructures may not exhibit physical properties (regarding conductivity or reactivity) desirable for certain applications. The properties could be in principle changed by mixing two or more metals together. By changing component ratio we can tune physical properties of the grown structures and strengthen or suppress particular features. There may be also a strong economic pressure to investigate multicomponent systems. Combination of cheap materials can reduce price while preserving or even improving physical properties of structures based on more expensive materials.
Growth of bimetallic structures on Si(100)-(2×1) surface is not well understood and detailed description, based on observation on atomic level, is still missing. We present a scanning tunnelling microscopy study of co-deposition of silver and indium on the Si(100)-(2×1) surface at room temperature and at various metal ratio. It is known , that indium itself forms atomic chains on the Si(100)-(2×1) surface [1], while Ag creates very unstable 2D islands [2]. The picture changes dramatically in case of co-deposition of the two metals. We observed mostly 2D islands formed from chains in case of co-deposition of the metals or deposition of indium onto silver layer. In case of deposition of silver onto indium layer mostly isolated chains mixed from the two metals are grown , unless the layer is annealed to higher temperature. Otherwise 2D islands are formed. Silver incorporates into or decorates the indium chains and connects them by perpendicular rails, so that complicated 2D structures are formed on the surface. Observation of time evolution of the grown layer and its relaxation, helps also to better understand involved atomic processes. The STM images of bimetallic structures are taken at both polarities of the tip in order to identify single species on the surface due to the different contrast in STM images.
[1] Baski A. A., Nogami J., Quate C. F., J. Vac. Sci. Technol. A, 9 (3), 1946, 1991
[2] Kocan P., Ostadal I., Sobotik P., Surf. Sci., 600 (2006), 3928 |