Khalifa Al-Azri

Synthesis of β-Silicon carbide nanowires by a simple, catalyst-free carbo-thermal evaporation technique

β-SiC nanowires were successfully fabricated on pare Si (100) substrate using simple carbo-thermal evaporation of graphite at 1200°C. The obtained β-SiC nanowires were aligned with diameters ranged between 40 to 500 nm. The majority of crystal planes were β-SiC (111) with other less intensity of (200), (220) and (311). The silicon substrate location inside the furnace found to be critical in the formation of the β-SiC nanowires. Also, FTIR absorption peaks for β-SiC nanowires found at higher frequency side of 1110 cm-1 which is pointed to Si–O asymmetric stretching mode.

Comparative Study of P-Doped and Undoped ZnO Nanostructures Using Thermal Evaporation and Vapor Transport Method

We report the synthesis of phosphorus-doped (P-doped) and undoped ZnO nanostructures using a thermal evaporation and vapor transport on Si(100) substrate without any catalyst and at atmospheric argon pressure. The structural and optical properties of P-doped ZnO nanostructures and undoped ZnO nanostructures have been extensively investigated using filed emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and Photoluminescence (PL). FESEM observation reveals that the morphology of ZnO nanostructures was changed from a hexagonal-like shape to a spherical shape when doping with P. While, XRD results indicate that P-doped ZnO nanostructures lost the (002) orientation preference and became randomly oriented. In addition, shifting of (002) diffraction peak has been found due to the incorporation of P into ZnO. Room temperature (PL) spectrum of P-doped ZnO nanostructures shows a high efficiency of green emission which was attributed to the presence of phosphorus atoms in the ZnO nanostructures.

Synthesis and photoluminescence of SiO x nanowires and aligned nanocakes for solar cell applications

The growth of SiOx nanowires and nano-cakes on Au-coated n-type-Silicon (100) substrate via carbothermal evaporation were studied. The standing nanowires were preferred in solar cells to gain more energy. The effects of the Au layer thickness and rapid heating rate on the morphology of obtained SiOx nanowires were investigated. A broad emission band from 290 to 600 nm is observed in the photoluminescence (PL) spectrum of these nanowires. There are four PL peaks: one blue emission peaks 485 nm (2.56 eV) two green bands centred at 502 nm (2.47 eV) and 524 nm (2.37 eV) for nanocakes and one ultraviolet emission peak at 350 nm (3.54 eV) and a hemisphere curve over the bluish green area taken for SiOx nanowires. These emissions may be related to the various oxygen defects and twofold coordinated silicon lone pair centres.

Parametric study on ZnO nanostructures for solar cell applications

A study on the formation of ZnO nanostructures using the carbothermal evaporation method without catalyst and at atmospheric argon pressure has been conducted. The effects of the position of the substrates to the source and deposition time were investigated. The results of these parametric studies based on field-emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) spectrum and X-ray diffraction (XRD) analyses support the reduction-evaporation model for ZnO nanostructures formation using carbothermal evaporation. We suggested that ZnO nanostructures that have been synthesized in this work have potential applications in solar cells.

Amorphous SiOx Nanowires And Aligned Nano‐Cakes: The Growth Mechanism And Photoluminescence

The growth of SiOx nanostructures nanowires and nano‐cakes on Au‐coated n‐type‐Silicon (100) substrate via thermal evaporation were studied. The diameters of the obtained nanowires varied from 20 nm to about 260 nm and 100 nm to several microns in length. Based on SVLS growth mechanism, the yield obtained decreased as the argon flow rate increased. A broad emission band from 290 to 600 nm is observed in the photoluminescence (PL) spectrum of these nanowires. There are five PL peaks: two blue emission peaks 465 nm (2.67 eV) and 482 nm (2.57 eV) and two green bands centred at 502 nm (2.47 eV) and 506 nm (2.45 eV) and one ultraviolet emission peak at 350 nm (3.54 eV), which may be related to the various oxygen defects and twofold coordinated silicon lone pair centres. Detailed characterizations on the resulting nanostructures were carried out using field‐emission scanning electron microscopy (FESEM) and energy‐dispersed X‐ray spectroscopy (EDX) and X‐ray diffraction (XRD).

Fabrication and Characterization of ZnO Nanostructures Using Carbothermal Evaporation Technique on Silicon Substrates Using Gold as Catalyst

Nanostructures ZnO have been fabricated on gold coated silicon substrates by sintering the mixture of ZnO and graphite powders in air. The effects of the position of the substrates to the ZnO source, Ar gas flow rates and the furnace temperature were investigated. ZnO nanostructures have been characterized using field‐emission scanning electron microscopy (FESEM), Energy dispersive X‐ray spectroscopy (EDX) spectrum and X‐ray diffraction (XRD). XRD found peaks corresponding to hexagonal ZnO while, FESEM result indicated different morphologies of ZnO nanostructures with different size grown in gold coated silicon substrates. It has been found that the morphology of the ZnO nanostructures is strongly dependant to the location of the substrate and to the source evaporating temperature. While, gas flow rate plays a key role for changing the growth density and the size of ZnO nanostructures.