dc.description.abstract | As the device dimensions scale down to nanometer region, in-depth understanding the reaction mechanisms between the nanoscale metal thin film and semiconductor substrate will play an important role in defining the use of these
nanoscale building blocks in advanced nanodevices. Therefore, in this study,particular emphases are focused on the fabrication of large-area, 2D-ordered nickel and cobalt metal dot arrays and the interfacial reactions of nickel and cobalt metal dots on Si substrates after different heat treatments.
To fabricate large periodic arrays of Ni and Co metal nanodots on silicon substrate, an effective and economical technique –polystyrene nanosphere lithography (PS NSL) was utilized. After 20-nm-thick metal thin films deposition and
subsequent lift-off of the PS spheres template, an ordered hexagonal array of triangular metal dots was formed on the surface of Si substrate.
From the SEM, TEM, and SAED analysis, epitaxial NiSi2 and CoSi2 nanodot arrays were found to form at a temperature as low as 350 ℃ and 550 ℃, respectively. The orientation relationships of epitaxial metal disilicide nanodots with respect to
(001)Si substrates were identified to be [001] NiSi2 (or CoSi2) // [001] Si and (200)
NiSi2 (or CoSi2) // (400) Si. The results indicated that the growth of epitaxial NiSi2
and CoSi2 is more favorable for the metal dot array samples. In addition, the sizes of
the silicide nanodots were found to decrease with annealing temperature. The epitaxial
metal disilicide nanodots were identified to be inverse pyramids in shape. The bases
of the pyramidal metal disilicide nanodots are parallel to the (001)Si wafer surface and
the faceted edges of the bases of the pyramids are along the <1 1 0> Si directions. The
epitaxial metal disilicide nanodot/Si interfaces were found to be faceted with {1 1 1}interface planes. Furthermore, for the nickel nanodot samples annealed at 900 ℃,amorphous SiOx nanowires were found to grow on individual nickel silicide nanoparticles. The diameters of these nanowires are in the range of 15–20 nm, and the growths of a-SiOx were controlled by the solid-liquid-solid (SLS) mechanism.
On the other hand, by tuning the drop-coating processes and lift-off conditions,hexagonal periodic nanoring arrays were successfully fabricated on (001)Si substrates. In addition, the diameters of nanorings can be controlled by adjusting the concentration of surfactant. Based on the results of a series of observation and
analysis, the possible formation mechanism of nanoring arrays might be related to the
normal capillary force deforms PS spheres during the drying of a suspension droplet. | en_US |