The growth of metal films on semiconductors is of interest in the fabrication of miniaturized semiconductor devices, including integrated circuits, microelectronics and opto-electronics. Amongst the numerous systems in this field, the growth of Ag-films on Si(001) has been heavily examined, since it serves as a prototype model for an abrupt metal/semiconductor interface. More recently, the absence of silicide formation was also highlighted in the inverse epitaxial process, in which silicene was synthesized from the growth of silicon on Ag(111). Here, we present studies on the adsorption, growth and dewetting dynamics of silver on Si(001).First, we examined the atomistic structure of the silver films formed on Si(001) at room temperature. It had been long assumed that silver dimers, Ag2, served as the fundamental unit of the film. By using Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT) simulations, we show that it is a tetramer structure, Ag4, that accounts for the (2x1) and (2x2) periodicities of the silver film. Second, we examined the growth dynamics of silver film on Si(001); that is on how Ag-tetramers are formed from individual silver adatoms upon deposition, and on how Ag-tetramers assemble into an extended silver film. By varying the substrate temperature between 100 K and 230 K, STM measurement identified three growth stages en route to forming an extended silver film, each exhibiting distinct dynamics. Our results demonstrate the complexity in epitaxial film growth, as resulted from the hot-atom motion upon the monomer adsorption of deposits, and the migration of adsorbed aggregates of a variety of sizes. Third, we present preliminary results that relate to the thermal stability of silver film on Si(001), i.e. the dewetting dynamics. Extended in-situ monitors of the film evolution between 245 K and 276 K, unambiguously demonstrate the dewetting of the silver film, from which the relevant energetics are determined. Complementary measurements, using annealing/quenching method, gave evidences that the dewetted Ag forms as clusters migrating over both naked and silver-covered silicon surfaces. Additionally, the dewetting of silver film was found to be enhanced in the vicinity of three-dimensional silver islands.

Adsorption, growth and dewetting dynamics of silver on Si(001)

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