Search

Thin Film Technology has attracted attention of the numerous investigators all over the world owing to its huge applications in a variety of fields such as optics, electronics, lasers, blue-green light emitting diodes and industries also. There are a variety of deposition techniques by which a host of thin semiconductor films can be deposited. Among these deposition technologies, chemical bath deposition (CBD) is ranked as conceptually simplest and universal. In this paper, we report on the synthesis of Zn1-xCoxSe (0 = x = 0.275) thin films grown from the aqueous solutions of zinc sulphate, cobaltous sulphate and selenium metal ions in the presence of TEA as a complexing agent, hydrazine hydrate as a reducing agent and ammonia to enhance the film adherence. ZnSe and Co doped ZnSe films were prepared at 80°± 1° C; the deposition time being 90 mins. The surface of the asobtained films were smooth, uniform and hydrophobic in nature. The X-ray photoelectron spectroscopy confirmed the presence of Zn, Co and Se. As the constituent elements in the deposited films are having 2+, 2+ and 2- chemical states. Both ZnSe and Zn1-xCoxSe thin films are crystalline over the whole composition range (0 = x = 0.275) and are structurally cubic. The lattice parameter (a) and interplanar distance (d) change with the addition of Co2+ in the ZnSe host lattice. Formation of ternary alloy was confirmed from the shift in the (111) X-ray diffraction peak. AFM surface topography revealed the influence of Co2+ integration into ZnSe host lattice, the film sample with x = 0.15 being more crystalline with Sku = 5.572, maximum surface area ratio (Sdr) and highest average roughness (Sa). Increasing amount of Co2+ in the ZnSe lattice results in the sample surface transformation from mesokurtic (less sharp or crystalline) to leptokurtic (crystalline or more sharper). The advanced imaging Sobel transformation and angular spectrum techniques provided a better visibility of the fine structure and features of the various materials. [ABSTRACT FROM AUTHOR]

We present a study of the spectral photoresponse (SPR) of ZnSe/GaAs(001) heterostructures for different ZnSe film thickness with and without CdSe ultra-thin quantum well (UTQW) insertions. We observe a significant increase of the SPR of heterostructures containing 3 monolayer thick CdSe UTQW insertions; these results encourage their use in photodetectors and solar cells. [ABSTRACT FROM AUTHOR]

The single layer of ZnSe has been studied to understand the structure using density functional theory. The vibrational frequencies of several cluster of ZnSe have been calculated when the Kohn-Sham equation solved at the ground state energy. We have done the calculation for 34 models of ZnSe clusters but only the stable molecules will be discussed. The bond length, Fermi energy and binding energy of ZnSe clusters have been calculated. The experimental result of single layer of ZnSe shown by Nesheva et. al. using different thickness of layers until 1μm [1]. The Raman spectra of ZnSe shown several peak for different thickness. In this paper, we will show the comparison of our calculated result with the experimental Raman spectra to show the existent of cluster. [ABSTRACT FROM AUTHOR]

ZnSe nanoparticles were prepared using a chemical bath deposition technique. X-ray diffraction study shows that the ZnSe crystallizes in the cubic phase. The crystallite size of the ZnSe samples calculated using the Scherrer's formula was found to be slightly smaller than the Bohr exciton radius of bulk ZnSe. SEM studies show the growth of a mixture of nanorods and spherical nanoparticles. EDAX analysis confirms that the synthesized ZnSe nanoparticles are of good stiochiometry. Optical studies show the blue shift in the absorption edge for ZnSe nanoparticles caused by quantum confinement. [ABSTRACT FROM AUTHOR]

The conduction band offset between strained CdSe layers embedded in unintentionally n-type doped ZnSe is measured and reported. Two samples, consisting of thirty Ultra Thin Quantum Wells (UTQWs) of CdSe embedded in ZnSe, grown by Atomic Layer Epitaxy, are used for this study. The thicknesses of the UTQWs are one and three monolayers (MLs) in each sample, respectively. As expected, the sample with one ML UTQWs does not show any energy level in the UTQWs due to the small thickness of the UTQWs, while the thickness of the sample with 3 ML UTQWs is large enough to form an energy level inside the UTQWs. This energy level appears as a majority trap with an activation energy of 223.58 ± 9.54 meV. This corresponds to UTQWs with barrier heights (the conduction band offset) between 742 meV and 784 meV. These values suggest that the band gap misfit between strained CdSe and ZnSe is around 70.5 to 74 % in the conduction band. [ABSTRACT FROM AUTHOR]

CdSe ultra-thin quantum wells (UTQWs) can be grown by atomic layer epitaxy (ALE) without thickness fluctuations. However, the evolution of the excitonic peak energy as a function of temperature exhibits an S-shaped curve typical of potential fluctuations. These are originated from small interface composition fluctuations, as evidenced by the larger amplitude of the S-curve of a 2.5 monolayer (ML) CdSe UTQW, finished with a fractional ML, compared to the results for a 3 ML UTQW. [ABSTRACT FROM AUTHOR]

We demonstrate time- and depth-resolved holographic imaging of reflecting objects using the all-optical phase coherent photorefractive effect in ZnSe quantum wells. Since these quantum well structures use the coherence of excitons as a basis for holography the depth information of an object can be obtained from the brightness profile of its holographic image with a resolution of a few micrometers. [ABSTRACT FROM AUTHOR]

We report on Au catalyst-assisted molecular beam epitaxy growth and properties of pure ZnSe and ZnSe/CdSe superlattice nanowires. In particular, we concentrate our attention on the morphological characterization by transmission and scanning electron microscopy of pure ZnSe NWs and we compare their optical properties with those of ZnSe/CdSe superlattice NWs fabricated at the same technological conditions. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Atomistic structure of ZnSe needle-like nanowires on a ZnSe/GaAs(001) epitaxial layer, grown catalytically by means of molecular beam epitaxy operated at low temperatures (527 or 573 K), was studied. A nanowire was the zinc blende structure. The diameter at the top was in the range from 8 to 20 nm, and the length was about 200 nm. It was implied that the optical property differs from that of the bulk crystals, presumably due to the wire confinement effect. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Pressure-Raman spectra are compared for bulk crystalline 68Zn76Se and ZnSe nanorods. The broadening of TO(Γ) and LO(Γ) is explained by multiphonon mixing and the position of a gap in the 2-phonon DOS. Nucleation of the phase transition in 68Zn76Se leads to striking similarities in the Raman spectra of retrieved bulk and nanorod samples. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present a study of the deep level emission of n-type doped ZnSe films as a function of Cl concentration with the purpose to identify features related to the incorporation of Cl at non-electrically active sites. The initial incorporation of Cl improves the electrical properties of the ZnSe film but further doping degrades the excitonic emission and induces the presence of the SA band. The degradation of the electrical properties appears to be related to deeper energy levels with emission below 2 eV. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]