In-situ TEM Observation of Repeating Events of Nucleation in Epitaxial Growth of Nano CoSi₂ in Nanowires of Si

Abstract

The formation of CoSi and CoSi 2 in Si nanowires at 700 and 800°C, respectively, by point contact reactions between nanodots of Co and nanowires of Si have been investigated in situ in a ultrahigh vacuum high-resolution transmission electron microscope. The CoSi 2 has undergone an axial epitaxial growth in the Si nanowire and a stepwise growth mode was found. We observed that the stepwise growth occurs repeatedly in the form of an atomic step sweeping across the CoSi 2 /Si interface. It appears that the growth of a new step or a new silicide layer requires an independent event of nucleation. We are able to resolve the nucleation stage and the growth stage of each layer of the epitaxial growth in video images. In the nucleation stage, the incubation period is measured, which is much longer than the period needed to grow the layer across the silicide/Si interface. So the epitaxial growth consists of a repeating nucleation and a rapid stepwise growth across the epitaxial interface. This is a general behavior of epitaxial growth in nanowires. The axial heterostructure of CoSi 2 /Si/CoSi 2 with sharp epitaxial interfaces has been obtained. A discussion of the kinetics of supply limited and source-limited reaction in nanowire case by point contact reaction is given. The heterostructures are promising as high performance transistors based on intrinsic Si nanowires.

Growth of Crystalline Copper Silicide Nanowires in High Yield within a High Boiling Point Solvent System

“…To date, a variety of metal silicide NWs have been formed including NiSi, 2 FeSi 3 and CoSi 4 . The diffusivity of the metal in Si, is the strongest driving force for silicide formation with Ni showing high diffusivity resulting in a wide range of stoichiometries with six different phases successfully reported.…”

Structure, Growth Kinetics, and Ledge Flow during Vapor−Solid−Solid Growth of Copper-Catalyzed Silicon Nanowires

“…Similar recurrent halting in ledge propagation, which may result from defects at the interface, was observed in Pd 2 Si-catalyzed Si nanowire growth. 29 It is unlikely to happen in a system with a coherent interface, such as CoSi 2 /Si, 38 or with a liquid catalyst. Real-time measurements of the ledge flow kinetics, such as those shown in Figure 5, indicate that the "incubation time" defined above is typically less than 20% of the time between consecutive ledge nucleation events, and the average ledge propagation speed is relatively slow (10 nm/s).…”

Growth of single-crystalline cobalt silicide nanowires with excellent physical properties

“…1-3 Transition-metal silicide nanowires are the extremely broad set of refractory materials, and were widely researched for their unique physical properties, low resistivity, and excellent compatibility with contemporary silicon device processing. [4][5][6][7][8][9][10][11][12] With the advancement in nanoelectronics, the synthesis and properties of the silicide and silicide=semiconductor nanoheterostructures have received increasing attention. [13][14][15][16][17] For synthesis, high aspect ratios (length=diameter) transition silicide nanowires, we can use chemical vapor deposition (CVD) 18,19 or chemical vapor transport (CVT) 14,20 methods.…”