IN SITU STUDY BY GISAXS OF THE KINETIC OF FORMATION AND GROWTH OF CoSi2 NANOPLATELETS IN Si(001)

DANIEL COSTA; CRISTIÁN HUCK IRIART; LISANDRO GIOVANETTI; GUINTHER KELLERMANN; ALDO FELIX CRAIEVICH; FELIX G. REQUEJO

Berlin

Congreso; 16th Conference on Small Angle Scattering; 2015

An in situ study by grazing incidence small angle X-ray scattering (GISAXS) was performed to elucidate the mechanisms of formation and growth of: (i) spherical Co nanoparticles embedded in a SiO2 thin film deposited on a Si(001) wafer and (ii) hexagonal CoSi2 nanoplatelets endotaxialy buried in the Si(001) substrate, during isothermal annealing at 700 ºC. GISAXS patterns were recorded every 2 min during thermal treatment, over a total period of ~180 min. Figure 1 shows the 2D GISAXS intensity patters for the indicated thermal treatment periods.Our results evidenced the formation of spherical Co nanoparticles embedded in a SiO2 thin film promoted by the diffusion of Co atoms through the SiO2 thin film and the diffusion of Co atoms across the SiO2/Si(001) interface into a Si(001) wafer leading to the formation ofhexagonal CoSi2 nanoplatelets. The sizes of Co nanoparticles continuously grow during the annealing while their number density progressively decreases thus leading to a coarsening of the overall particle structure.Simultaneously, Co atoms diffuse into the Si substrate, react with Si atoms and build-up CoSi2 hexagonal nanoplatelets. All nanoplatelets have their large surface parallel to Si{111} crystallographic planes with their lattice coherent with the host Si lattice. Since the totalvolume of Co nanoparticles embedded in the SiO2 thin film decreases while the total volume of CoSi2 nanoplatelets buried in Si(001) increases, we concluded that the growth of CoSi2 nanoplatelets occurs at theexpense of the dissolution of the relatively smaller Co nanoparticles.In order to obtain all relevant parameters from the experimental GISAXS intensity, we have applied a newly developed routine for full-pattern fitting, which takes into account the experimental counting ratescorresponding to all accessible pixels.