Mechanics of the ion layer gas reaction–A preparation method of nanocrystalline thin layers

Nanocrystalline CdS thin layers can be prepared using the ion layer gas reaction (ILGAR), a low-cost deposition technique for compound semiconductor thin films. We investigated the layers by optical spectroscopy and transmission electron microscopy, and found that lower ${\mathrm{CdCl}}_2$ precursor concentrations and thicker films favor larger nanoparticles and a lower band gap energy, whereby the concentration effect is more pronounced. The nucleation mechanism of the ${\mathrm{CdCl}}_2$ precursor seems to determine the particle size and the probability of its growth. A minimum CdS particle diameter of 4.7 nm has been extrapolated, which corresponds to an optical band gap energy of 2.83 eV, as a result of quantum confinement. ILGAR enables deposition of nanoparticles of controlled size.