AFM study of templated growth of cadmium sulfide nanoparticles using pure and mixed arachidate films

Langmuir-Blodgett (LB) multilayers of arachidic acid (AA) and octadecylamin e (ODA) were used as templates in order to produce cadmium sulfide (CdS) na noparticle arrays. Both atomic force microscopy (AFM) and X-ray photoelectr on spectroscopy (XPS) were used to characterize the film. In the absence of ODA, the cadmium arachidate: trilayers were highly crystalline with a latt ice constant of 0.42 nm. Upon reaction with hydrogen sulfide (H2S), an orde red array of CdS nanoparticles with a particle separation of 4.2 nm was ima ged. The existence of CdS was also confirmed by XPS. No CdS nanoparticles w ere formed when ODA was used as the sole component. In the presence of ODA, the crystalline structure of the AA film was disturbed, resulted in random ly distributed particles. The average particle height was reduced from 4 to 1 nm when the amount of ODA was increased. It is concluded that there is a direct correlation between the ordering of the organic template and that o f the nanoparticle array. There is also a correlation between the particle size and the ratio of AA and ODA. Mixed LB films are promising in synthesiz ing semiconducting nanoparticle arrays of limited particle sizes. (C) 2000 Elsevier Science S.A. All rights reserved.