Morphology of CdSe films prepared by chemical bath deposition: The role of substrate

We combine optical spectroscopy and transmission electron microscopy to study the growth and the structural morphology of CdSe films prepared by chemical bath deposition (CBD) on two considerably different substrates. The films grown on glass are compact and strongly adherent to the substrate. On the contrary, the films deposited on carbon-coated glass (with approx. 20 nm thick amorphous carbon layer) are only loosely adherent to the substrate. Using transmission electron microscopy we revealed that even though the films grown on both substrates are assembled from closely spaced nanocrystals with diameter of about 5 nm, the films morphology on the sub-micrometer scale is considerably different in the two cases. While the films deposited on glass are rather compact, the films prepared on carbon layer have high porosity and are formed by interconnected spheres which size is dependent on the duration of deposition (e.g. 155 nm for 6 h and 350 nm for 24 h). This shows that the choice of the substrate for CBD has a stronger influence on the sub-micrometer film morphology than on the properties of individual nanocrystals forming the film.