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A new technique for the preparation of normalCdS thin films by chemical bath deposition is described. The normalCdS films prepared by this method have many of the advantages of those made by the spray deposition method, such as the ease of coating large areas and simplicity of the process. The stoichiometry is easy to maintain in both these methods. The films are formed on rotating substrates from a bath containing cadmium salt in a complex form. Electrical, photoconducting, and optical properties such as I–V characteristics, decay of photoconductivity, spectral response of photoconductivity, and optical absorption were studied. Addition of cations like Ag, Cu, In, and Zn to the deposition bath makes the films amorphous. Such amorphous layers have a density of state of the order of 1019–1020/cm3/eV near the Fermi level, as determined by photodecay and field effect measurements. The films produced are strong, adhering tightly to the substrates, show little or no degradation, and are photosensitive as deposited.

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Large quantities of extremely fine aragonite needles (see Figure, top image) have been synthesized at room temperature at an expanding liquid–liquid interface in a radial Hele–Shaw cell. By simple variation of the experimental conditions, hollow, cylindrical aragonite/calcite crystals (see Figure, bottom image) may also be obtained. It is believed that this method can be extended to other materials and nanostructures.

Electroluminescence from heterojunctions fabricated by depositing ultrathin films of nanocrystalline CdS and ZnS on porous silicon by the liquid–liquid interface reaction technique is reported. Junction current–voltage characteristics were studied for different thicknesses of the deposited films. Large forward currents on the order of 180 mA/cm2 and a rectification ratio on the order of 103 were characteristic of the diode. The reverse breakdown voltage on the order of 150 V indicated the stability of these diodes. Electroluminescence was observed to arise at around 625 nm, which was blueshifted as compared to the photoluminescence peak and showed much smaller full width at half maximum (∼40 nm).