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. © 2012 Penerbit UTM Press. All rights reserved

Carbon assisted growth and photoluminescence of silicon nanowires fabricated without a catalyst

One-dimensional (1D) silicon nanowires (SiNWs) were fabricated on a catalyst free Si (100) substrate using a thermal evaporation method. Based on a SVLS growth mechanism, the SiNWs obtained were 30-265 nm in diameter and 1.7 mu m to several tens of microns in length. It was found that the presence of graphite powder alone is enough to accomplish the growth. A systematic study of how the growth conditions, such as the Ar carrier gas flow rate, and the growth time effect was performed. The Photoluminescence (PL) of SiNWs was also investigated. The observed broad band is composed of an UV peak or band centered at 350 nm (3.54 eV) and a wide hemisphere curve over the green bluish region (430-550 nm). The theory behind these emissions is discussed

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. © 2012 Penerbit UTM Press. All rights reserved

Direct growth and Photoluminescence of SiOx nanowires and aligned nanocakes by simple carbothermal evaporation

The growth of SiOx nanowires and nanocakes on an Au-coated n-type-Silicon (100) substrate was achieved via carbothermal evaporation. The effects of the Au layer thickness and the rapid heating rate on the morphology of obtained SiOx nanowires were investigated. A broad emission band from 290 to 600 nm was observed in the photoluminescence (PL) spectrum of these nanowires. There are four PL peaks: one blue emission peak 485 nm (2.56 eV) two green bands centered 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 centers

Synthesis of amorphous SiOx nanowires and nanofibers by thermal evaporation with gold as catalyst

The growths of SiOx nanostructures (nanowires and nanofibers) on Au-coated n-type-Silicon (100) substrate via thermal evaporation were studied. Based on SVLS growth mechanism, the obtained diameter of the nanowires varies between 13 nm and about 243 nm and the diameter of nanofibers found to be around 8 nm to 30 nm. The SiOx nanowires are 194 nm to several microns in length, but the length of SiOx nanofibers are 50 nm to several microns. It was found that the carbo-thermal reactions played an important role to accomplish the growth