J.J. Hassan

High sensitivity and fast response and recovery times in a ZnO nanorod array/p-Si self-powered ultraviolet detector

High quality, vertically aligned ZnO nanorods were grown on a silicon substrate, using microwave-assisted chemical bath deposition with poly (vinyl alcohol)-Zn(OH)2 nanocomposites as seed layer. The structure and surface morphology of the prepared ZnO nanorod arrays were characterized using X-ray diffraction and scanning electron microscopy. The optical properties were assessed using photoluminescence measurements; the results showed a high-intensity UV peak, and a lower intensity, broader visible peak. Upon exposure to 395 nm light at a zero-bias voltage, the UV detector showed a high sensitivity of 8000% and fast response and recovery times of 25 and 22 ms, respectively.

Solvothermal growth of single-crystal CdS nanowires

Cadmium sulfide (CdS) nanowires (NWs) were prepared by the solvothermal method using ethylenediamine as a solvent. Two sets of CdS NWs were synthesized at 160 and 200 °C for various reaction durations (3⋅5, 7, and 24 h). Scanning/tunneling electron microscopy was used to examine the surface morphology of the grown NWs. Their dimensions are found to depend on the reaction temperature and duration. The CdS NWs grown at 200 °C for all durations are longer than those prepared at 160 °C, with diameters ranging from 15 to 40 nm. A three-armed structure is exhibited by all the samples. The grown CdS NWs display a hexagonal wurtzite phase and grows along the 001

Fast UV detection and hydrogen sensing by ZnO nanorod arrays grown on a flexible Kapton tape

\mathbf {\left \langle {001}\right \rangle }

High-Quality ZnCdS Nanosheets Prepared Using Solvothermal Synthesis

direction. The optical absorption of the grown NWs shows a sharp absorption edge with a blueshift, which indicates an expansion of the optical band gap. All prepared samples show two emission peaks in their photoluminescence spectra. The emission peak location depends on the reaction temperature and duration. The CdS NWs prepared at 160 °C show a sharp band–band emission compared with those prepared at 200 °C. Raman analysis indicates that the optical properties of the grown NWs are enhanced with increased temperature and reaction duration.

Fabrication and Characterization of Porous CdS/Dye Sensitized Solar Cells

ZnO nanorod arrays were grown on a flexible Kapton tape using microwave-assisted chemical bath deposition. High crystalline properties of the produced nanorods were proven by X-ray diffraction patterns and field emission scanning electron microscopy. Additionally, the photoluminescence spectrum showed higher UV peaks compared with visible peaks, which indicates that the ZnO nanorods had high quality and low number of defects. The metal-semiconductor-metal (MSM) configuration was used to fabricate UV and hydrogen gas detectors based on the ZnO nanorods grown on a flexible Kapton tape. Upon exposure to 395 nm UV light, the UV device exhibited fast response and decay times of 37 ms and 44 ms, respectively, at a bias voltage of 30 V. The relative sensitivities of the gas sensor made of the ZnO nanorod arrays, at hydrogen concentration of 2 %, at room temperature, 150 °C and 200 °C, are 0.42, 1.4 and 1.75 respectively.

Preparation and characterization of ZnxCd1?xS ternary alloys micro/nanostructures grown by thermal evaporation

For the first time, nanosheets with different Zn and Cd ion concentrations were prepared using solvothermal synthesis at 200°C for 4 and 24 h. The crystalline structure of the nanosheets was wurtzite. The optical band gaps of the nanosheets increased with increasing Zn ratio; this increase is consistent with the band gaps estimated using Vegard’s formula. The photoluminescence spectra for the 24 h nanosheets had higher emission intensities than those for the 4 h nanosheets. The emission band corresponding to intrinsic near-band-edge emission and a broad peak associated with extrinsic deep-level emission were observed in the photoluminescence spectra.

Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

Dye sensitized solar cells (DSSCs) are fabricated from porous cadmium sulfide (CdS) nanocrystalline thin films. The porous CdS nanostructured thin films are deposited onto FTO/glass substrates by the chemical bath deposition (CBD) method. The surface morphology, crystalline structure, and optical properties of the prepared nanocrystalline thin films are investigated. Rhodamine B, Malachite green, Eosin methylene blue, and Cresyl violet dyes are used to fabricate the DSSC devices. Comparing the absorption spectra of porous CdS nanocrystalline films, all dyes show an absorption peak in the transparent range of CdS thin films indicating that they are suitable for the preparation of DSSCs with CdS. Current-voltage () characteristics show that the solar cell that is fabricated using Malachite green dye shows the highest conversion efficiency of 0.83% while using Rhodamine B dye produces a solar cell with lowest efficiency of 0.38%. However, heat treatment of the fabricated solar cells causes significant enhancement in the output of all devices.

A high-sensitivity room-temperature hydrogen gas sensor based on oblique and vertical ZnO nanorod arrays

Ternary alloy zinc cadmium sulfide (ZnxCd1−xS) micro/nanostructures were prepared onto various substrates using a thermal evaporation method. Morphological, structural, and optical properties were found to depend on growth temperature and substrate type. ZnxCd1−xS microparticles and flower-like structures were grown onto ITO-glass and Si(100) substrates at 520 °C. Microrods and nanosheets were formed on alumina and Si(100) substrates at 900 °C, as shown in scanning electron microscopy images. X-ray diffraction patterns confirmed that all prepared samples had a high-quality wurtzite (hexagonal) structure. The prepared samples emitted two bands, namely, a sharp one located in the green region corresponding to the near band edge and a broad band in the yellow region resulting from deep-level transition. The green photoluminescence peak location of the prepared samples blue shifted compared with the optical bandgap of bulk CdS, indicating that the prepared ZnxCd1−xS possessed a greater optical bandgap than that of CdS because of the Zn ratio.

High-quality vertically aligned ZnO nanorods synthesized by microwave-assisted CBD with ZnO–PVA complex seed layer on Si substrates

Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicone substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.