CdSe epitaxial films and nanostructures grown by the isothermal closed space sublimation technique

The use of the isothermal closed space sublimation technique for growing CdSe very thin films and nanostructures is reported. In this technique, the samples are grown by exposing a substrate alternately to elemental sources of Cd and Se. The whole system is at the same temperature, so the only driving force for the film growth is the vapour pressure difference between the elemental source and the film surface. This is due to the difference in chemical potential between the pure elements and the elements when forming the compound. Between subsequent exposures the surface is exposed to the carrier vapour. In this step, re-evaporation of the non-stable outermost part of the films can be controlled. This procedure leads to a self-regulated growth rate in which the size of the deposited materials is controlled very accurately. In this way, nanostructures and epitaxial thin films of CdSe were grown on single-crystal substrates. For the nanostructure growth a nanoporous anodic alumina membrane (AAM) was interposed between the elemental sources and the substrate. Optical and structural properties of the structures are reported. The structural characterization using x-ray diffraction and high resolution electron microscopy reveals the epitaxial quality of the films and the chemical composition and morphology of the semiconductor filled AAM samples.