Formation of CdSe nanoclusters in SiOx thin films

CdSe nanoclusters embedded in silicon oxide layers are produced by sequenti al physical vapor deposition of SiOx (x approximate to 1.5) and CdSe on cry stalline silicon substrates at room temperature. High-resolution electron m icroscopy is used to prove the formation of CdSe nanoclusters as well as to study their shape, size and structure. Cross-sectional electron micrograph s of the as-deposited samples reveal clusters with nearly spherical shapes, which are not arranged in a plane. The spatial distribution of the CdSe cl usters follows the surface morphology of the SiOx films. The average size o f the nanoclusters is about two times greater than the nominal thickness of the CdSe layers deposited. Upon annealing the samples at 670 K for 80 min, a slight size increase is observed accompanied by some improvement in crys tallinity of the CdSe nanoclusters. The sigma/a ratio (a: average size of n anocrystals, sigma: half-width at half-maximum of size distribution) found for 1-nm CdSe deposited on 20-nm SiOx is 0.13-0.14, while for 2-nm CdSe dep osited on 40-nm SiOx it is 0.19. (C) 2000 Elsevier Science Ltd. All rights reserved.