BI NANOCRYSTALS EMBEDDED IN AN AMORPHOUS-GE MATRIX GROWN BY PULSED-LASER DEPOSITION

Bi nanoclusters embedded in an amorphous Ge matrix have been produced by alternate pulsed laser deposition in a vacuum. The resulting thin f ilms have been analyzed by high resolution electron microscopy, and th e images show that the Ge matrix is amorphous and that Bi nanocrystals are formed. The size of the nanoclusters was easily changed within th e range 2 nm to 25 nm by varying the number of pulses on the Bi target . Both the dependence of the nanocrystal size on the number of laser p ulses on the Bi target and the results of tilting experiments in the e lectron microscope show that the nanocrystals have an oblate ellipsoid al shape with a much shorter axis in the direction of the film normal. This particular shape is related to their growth mechanism after nucl eation at the substrate.