Controlled growth of extended arrays of CoSi₂ hexagonal nanoplatelets buried in Si(001), Si(011) and Si(111) wafers

Abstract

Because of their high electrical conductivity CoSi2 nanostructures are potential candidates for preparing ordered nano-arrays to be used as electrode interconnectors and contacts in microelectronic devices. We here describe a controlled procedure for the endotaxial growth of hexagonal CoSi2 nanoplatelets buried in differently oriented single crystalline Si wafers on which a Co-doped SiO2 thin film was previously deposited. These nanomaterials were obtained by a clean procedure consisting of isothermal annealing at 750 °C under a He atmosphere of Co-doped SiO2 thin films deposited onto the surface of three differently oriented flat Si substrates, namely Si(001), Si(011) and Si(111). Buried CoSi2 nanoplatelets are in all cases spontaneously formed as a consequence of the diffusion of Co atoms into the silicon wafer and their reaction with host Si atoms. Our TEM and GISAXS analyses demonstrated that these arrays, irrespective of host Si orientation, consist of CoSi2 hexagonal nanoplatelets in all cases parallel to Si{111} crystallographic planes. Additionally, the dimensions of the nanoplatelets were consistently determined by TEM and GISAXS for the three different host Si single crystal orientations.

Self-templating noncatalyzed synthesis of monolithic boron nitride nanowires

“…Previous reports have concluded that the Si(111) plane is highly likely to form an interface with NWs. 17,20,23,24,26 However, in Fig. 5b, the interfacial angle between the Si(001) surface and the NW is $63 , which is parallel to crystallographic planes of the Si(102) form.…”

“…Increasing attention has been given to self-assembled endotaxial silicide NWs. 17,[22][23][24][25][26] The term "endotaxy", which was coined by Fathauer et al, 27 describes cases in which epitaxial growth occurs into the substrate. 17 Interesting and useful structures can be formed by endotaxy, as in nanoscale permeable base transistors 17 or thermoelectric devices.…”

In situ study of the endotaxial growth of hexagonal CoSi2 nanoplatelets in Si(001)

“…During the last decades, a number of authors have investigated the formation of nano-objects deposited to or grown on external surfaces of different single crystalline substrates. [1][2][3][4][5][6][7][8][9][10] The knowledge of the relevant features and the control of the growth processes of these nanostructures are of particular relevance because the properties of these materials strongly depend on the sizes and shapes of the basic building blocks. [11][12][13][14][15][16][17] In the particular case of silicides obtained by deposition of transition metals on silicon singlecrystals under ultra-high vacuum conditions, they selfassemble into high aspect ratio nanowires.…”

“…9 Interestingly, all buried CoSi 2 nanoplatelets are parallel to crystallographic Si{111} planes and have their lattice coherently related to the face centered cubic lattice of the Si host, regardless the silicon face in contact with the SiO 2 film (001, 011, or 111). 10 The formation of CoSi 2 nanoplatelets is the result of a complex combination of physicochemical processes-such as diffusion of atoms in solid phases and chemical reaction of Co with Si-leading to the final silicide. 19,31 The final size, shape, and ordering of the CoSi 2 platelets buried in Si(001) obtained after long periods of thermal treatments (1 h at 750 C) were determined in previous ex situ GISAXS and TEM studies.…”

“…19,31 The final size, shape, and ordering of the CoSi 2 platelets buried in Si(001) obtained after long periods of thermal treatments (1 h at 750 C) were determined in previous ex situ GISAXS and TEM studies. 9,10 However, the mechanisms involved in the processes of nucleation and growth of these nanoparticles are so far not known. In order to obtain new information related to the kinetics of the process and the mechanisms involved in the early stages of crystals nucleation and growth, the endotaxial growth of CoSi 2 nanoplatelets is here a)…”