INFLUENCE OF GROWTH-CONDITIONS ON THE STRUCTURAL-PROPERTIES OF CDSXSE1-X (X=0.4 AND X=1) NANOCRYSTALS

The structural properties of CdSxSe1-x nanocrystals elaborated by two different methods have been studied by means of high resolution transm ission electron microscopy and optical absorption. In the first method , CdS0.4Se0.6 nanocrystals are grown in glass matrix and show a size d istribution characterized by a standard deviation sigma nearly proport ional to the nanocrystals mean diameter d, the value sigma/d being abo ut 0.25. They are crystallized in the stable structure of wurtzite-typ e from the beginning of growth. Their morphology depends on the size: it changes from sphere to hexagonal prism as the size increases. In th e second method CdS nanocrystals are grown in solution and show narrow er size distribution; the ratio sigma/d is about 0.15. The structure d epends on the nanocrystal size: the blende-type structure is dominant at small diameter (d = 3 nm) and the wurtzite-type structure is more i mportant at larger diameter (d > 5 nm). Their morphology also changes from quasi-sphere at small size (< 4 nm) to polyhedron-like at larger size.