Abstract
Compound formation at a metal/semiconductor interface plays crucial roles in the properties of many material systems. Applications of Ni silicides span numerous areas and have the potential to be used as new functionalities. However, the magnetic properties of ultrathin Ni layers on silicon surfaces and related chemical compositions at the interface are not fully understood and the influence of Ag additives on the reactivity of Ni/Si(111) remain unclear. We report herein on the fact that the dominant species produced at the interface is NiSi, which is produced by the spontaneous formation of strong bonds between Ni and Si atoms. Assuming that a Ni layer is formed over a NiSi layer with the total coverage as a constraint, we established a chemical shift-related concentration model that, in effect, represents a practical method for determining the amount of ultrathin Ni silicides that are produced at the buried interface. The formation of Ag-Si particles provide a viable strategy for enhancing silicide formation via a specific interaction transfer mechanism, even at room temperature. The mechanism is related to differences in the enthalpies of formation ΔHAg-Si, ΔHNi-Ag, and ΔHNi-Si, for these phases and provides insights into strategies for producing ultrathin silicides at a buried interface.
Highlights
Metal-semiconductor interfaces have attracted considerable interest because of their promising applications as semiconductor devices and possible use as new functionalities in semiconductor technology[1,2,3,4,5,6]
Assuming that a Ni layer is formed over a NiSi layer with the total coverage as a constraint, we established a chemical shift-related concentration (CSRC) model that represents a practical method for determining the amount of ultrathin Ni silicides that are produced at the buried interface
For a submonolayer Ni deposited on a few monolayers of Ag/Si(111), the chemical state of Ni was found to be closer to that for Ni silicides rather than for Ni-Ag bonding
Summary
Metal-semiconductor interfaces have attracted considerable interest because of their promising applications as semiconductor devices and possible use as new functionalities in semiconductor technology[1,2,3,4,5,6]. Owing to the high chemical reactivity of semiconductor surfaces, the formation of compounds at metal/semiconductor interfaces plays crucial roles in determining the properties of material systems and open a wide range of applications[5,6,7,8,9,10,11,12,13,14,15,16,17]. Applications of Ni silicides span numerous areas, including their use in silicon complementary metal-oxide semiconductors[5,12], field effect transistors[11], batteries[46,47] and floating gate memory[22]. There are relatively few reports dealing with the magnetic properties of ultrathin Ni layers on silicon surfaces and chemical compositions of these materials at the interface. The mechanism is related to the differences in the enthalpies of formation ΔHAg-Si, ΔHNi-Ag, and ΔHNi-Si, and provide insights into strategies for producing ultrathin silicides at a buried interface
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