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Cd 1−x ZnxS nanocrystals are prepared by a co-precipitation method with different atomic fractions of Zn. The texture, structural transformation and optical properties with increasing x value in Cd 1−x ZnxS are studied with scanning electron microscopy, electron diffraction patterning, and absorption spectra respectively. Quantum confinement in a strained CdS/Cd 1−x ZnxS related nanodot with various Zn content values is investigated theoretically. Binding energies on exciton bound CdS/CdxZn 1−x S quantum dot are computed, with consideration of the internal electric field induced by the spontaneous and piezoelectric polarizations, and thereby the interband emission energy is calculated as a function of the dot radius. The optical band gap from the UV absorption spectrum is compared with the interband emission energy computed theoretically. Our results show that the average diameter of composite nanoparticles ranges from 3 nm to 6 nm. The X-ray diffraction pattern shows that all the peaks shift towards the higher diffracting angles with an increase in Zn content. The lattice constant gradually decreases as the Zn content increases. The strong absorption edge shifts towards the lower wavelength region and hence the band gap of the films increases as the Zn content increases. The values of the absorption edge are found to shift towards the shorter wave length region and hence the direct band gap energy varies from 2.5 eV for the CdS film and 3.5 eV for the ZnS film. Our numerical results are in good agreement with the experimental results.

The effect of electric-field strength on the binding energy of a hydrogenic impurity in an InAs/GaAs quantum wire is discussed. Calculations have been performed using Bessel functions as an orthonormal basis within a single-band effective-mass approximation. The electric-field-induced photoionization cross section of the hydrogenic impurity is investigated. The total optical absorption and the refractiveindex changes as a function of normalized photon energy between the ground and the first excited state under the influence of an electric field are analyzed. The optical absorption coefficients and the refractive-index changes strongly depend on the incident optical intensity and the electric-field intensity.1 Introduction A remarkable amount of work is devoted to the study the low-dimensional heterostructures such as quantum wells, quantum-well wires, and quantum dots due to their interesting basic physical properties and the possible potential applications such as in lasers, longwavelength photodetectors, optoelectronic devices, and other devices. The confinement of electrons and holes in these nanostructures modifies the electronic, optical, and vibrational properties of the materials. There has been increasing interest in the study of the electronic and optical properties of quantum-well wires whose dimensions are of nanometer size. In such structures, the electrons are confined to movement along the length of the wire while the motion in dimensions perpendicular to the wire is quantized. The understanding of the electronic and optical properties of impurities in these quantum wires is imperative because the optical, electrical, and transport properties of devices made from these materials will show exotic behavior when the size is reduced to nanodimensions.

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