Plane Of CdS Research Articles

Effect of Tb Doping on Structural and Optical Properties of (Cd0.8-Zn0.2)S Films Deposited Through a Chemical Route

Tb-doped (Cd0.8-Zn0.2)S films have been prepared on glass substrates at 60°C by a chemical bath deposition technique. The effect of variation in the molar concentration of terbium (Tb) on the optical properties of the deposited films has been investigated and is discussed. The films have been characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Vis absorption and photoluminescence (PL) emission spectral studies. Prominent diffraction lines of CdS and ZnS with maximum orientation towards (111)c plane of CdS are observed in XRD patterns. Particle sizes calculated from XRD studies using Scherrer’s formula are found to be in the nano-range. The SEM micrographs of bulk film showed a layered structure, while a honey-comb structure with thickness of layers in the nano-range is seen for the deposited films. From the optical absorption spectra, a blue shift in the absorption edge is distinctly observed in the nanocrystalline films as compared to bulk film, suggesting the involvement of a quantum confinement effect. PL emission spectra showed distinct emission peaks for bulk and nanocrystalline films. PL emissions due to transitions within Tb3+ levels are also observed. The characteristic green emission peak due to 5D4-7F2 transition in Tb at 620 nm is observed in all three cases. Various studies suggest that the deposited films have potential applications in photo-electronic devices.

Defect-Induced Epitaxial Growth for Efficient Solar Hydrogen Production.

Epitaxial growth suffers from the mismatches in lattice and dangling bonds arising from different crystal structures or unit cell parameters. Here, we demonstrate the epitaxial growth of 2D MoS2 ribbon on 1D CdS nanowires (NWs) via surface and subsurface defects. The interstitial Cd0 in the (12̅10) crystal plane of the [0001]-oriented CdS NWs are found to serve as nucleation sites for interatomically bonded [001]-oriented MoS2, where the perfect lattice match (∼99.7%) between the (101̅1) plane of CdS and the (002)-faceted in-plane MoS2 result in coaxial MoS2 ribbon/CdS NWs heterojunction. The coaxial but heterotropic epitaxial MoS2 ribbon on the surface of CdS NWs induces delocalized interface states that facilitate charge transport and the reduced surface state. A less than 5-fold ribbon width of MoS2 as hydrogen evolution cocatalyst exhibits a ∼10-fold H2 evolution enhancement than state of the art Pt in an acidic electrolyte, and apparent quantum yields of 79.7% at 420 nm, 53.1% at 450 nm, and 9.67% at 520 nm, respectively.

Synthesis, Structural and Optical Properties of PVP Encapsulated CdS Nanoparticles

Highly monodispersed CdS nanoparticles using polyvinyl pyrrolidone (PVP) as the capping agent were synthesised by chemical coprecipitation method. The surface-modified cadmium sulfide nanoparticles were found to be remarkably stable. In the presence of PVP, cubic phase with small grain size of CdS were observed in XRD. The peaks were identified to originate from (111), (220) and (311) planes of CdS, respectively. The crystallite size of the synthesised CdS nanoparticles was about 3 nm calculated from the (111) plane of XRD pattern and it was also confirmed through HRTEM. Morphology and elemental mapping of the synthesised nanoparticles were studied by SEM and EDX analyses. Increase in the band gap with decrease in the particle size was observed from the reflectance mode UV spectrum, which confirms the quantum confinement effect. From the photoluminescence studies, enhanced near-band-edge blue light emission and significantly reduced defect-related green emission were observed. Longitudinal optical (LO) phonon modes, corresponds to pure CdS were observed in Raman spectrum.

Photoluminescence and Raman Study of CdS–Al<SUB>2</SUB>O<SUB>3</SUB> Nanocomposite Films Prepared by Sol–Gel Techniques

The optical and microstructural properties of CdS-Al2O3 nanocomposite (CdS-Al2O3 = 20:80 to 50:50) thin films synthesized by sol-gel techniques were studied. Optical transmission spectra indicated a marked blue shift of the absorption edge due to quantum confinement. Band gaps of CdS-Al2O3 nanocomposites were found to vary in the range 3.69-2.61 eV. The sizes of the nanocrystals, estimated from the blue shift (0.2-1.2 eV) of the absorption edges and transmission electron microscopy, were found to vary in the range 2.8-7.0 nm. X-ray diffraction studies showed reflections from (111), (200), (220), and (311) planes of CdS in the cubic phase. Microstructural characterization by high-resolution transmission electron microscope (HRTEM) indicated well crystallinity of the nanoparticles and lattice fringes supported the cubic phase of CdS. Raman spectroscopy was carried out for CdS-Al2O3 nanocomposites, which indicated a prominent peak at approximately 299 cm(-1). Significant changes in the peak position and intensity of the Raman peak were observed with varying the annealing temperature (373-573 K). Photoluminescence measurements indicated a prominent broad peak at approximately 1.81 eV due to the surface defects in the CdS nanocrystallites. The present study revealed Al2O3 to be a good capping material for CdS nanoparticles.

Junction structure and physical properties of heteroepitaxial CdS/CdTe

Abstract The screen printed CdS/CdTe hetero-junctions formed on the (0001), (1120), (1010) surfaces of CdS single crystals have been studied by an X-ray double crystal spectrometer, electron diffraction, transmission electron microscopy (TEM), and EBIC. For CdS/CdTe formed on the CdS (0001) structure, the epitaxiality of the CdTe layer formed on (0001) of CdS was better than that formed on the other surfaces. The diffusion length of minority carriers formed on the single crystal CdS was found to be larger than that of sintered CdS/CdTe junction prepared by the screen printing method especially for the junctions grown on the (0001) plane of CdS.

Generation of metastable shallow donors induced by cooling in hexagonal II-VI semiconductors

A highly conductive layer is found to arise on a (0001) plane of CdS, CdSe and CdSSe crystals under cooling in darkness from 300 to 77 K. This effect is shown to be caused by the increase of free electron density in a thin (500-100 AA) subsurface layer. At 77 K, the free electron density in this layer reaches approximately 1018 cm-3. Detailed investigations of the dark conductivity, photoconductivity, Hall effect and bound exciton luminescence lead to the conclusion that the increase of conductivity is due to creation of metastable donors. This effect is supposed to be stimulated by both a pyroelectric field and mechanical stresses arising under cooling.

CdS ‐ PbS Heterojunctions

Heterojunctions between n‐type and p‐type were prepared by chemical deposition of films on single crystals. The films were found to grow epitaxially on crystals. The cubic (111) plane of was parallel to the hexagonal (002) plane of CdS and the cubic (220) plane to the hexagonal (110) plane. The heterojunctions showed a marked photovoltaic effect and distinct rectifying characteristics. The maximum open circuit voltage obtained was 0.4V under irradiation with a tungsten lamp at 0.3 w/cm2. The spectral sensitivity of the photovoltaic effect showed a sharp maximum at the absorption edge of and a flat plateau extending toward long wavelengths as far as 1µ. The junction capacitance at zero bias and diffusion voltage were measured to be , respectively. From these results the energy band diagram was constructed for the heterojunction.