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Catalyst free growth of single-crystalline bismuth nanorods by closed space sublimation technique

Usman W., Maqsood A.

Materials Science Poland

2015

Vol. 33, No. 2

381--390

In the present study, bismuth (Bi) thin films having thickness of 335 nm have been deposited onto a glass substrate by closed space sublimation (CSS) technique. Besides this, spontaneous growth of Bi nanorods has also been investigated for the first time, without template and catalyst assistance in a substrate temperature range of 380 to 430 degrees C using CSS technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate microstructure, morphology and roughness of the Bi nanorods. The diameter and length ranges of Bi nanorods were 80 to 400 nm and 3 to 5 mu m, respectively. Moreover, they exhibited a rhombohedral structure with a dominant peak indexed at (012), (104), and (110). The mass percentage of Bi, determined by energy dispersive X-ray (EDX), was 99.93 %. The studies of electrical resistivity, Hall coefficient, magnetoresistivity, hole mobility and carrier concentration of Bi thin films were performed at 300 to 350 K and the electrical properties were found to be a function of temperature. The basic aim was to investigate the spectacular evolution of Bi nanostructures on as-deposited thin films and effects of thickness on their structural, electrical and dielectric properties. Detailed examination of SEM micrographs eliminated all other growth modes except self-catalytic tip growth by Vapor-Solid (VS) growth process which is believed to provide the driving force for spontaneous nanorod growth at high substrate temperature. Deposition of thinner Bi films provided a new possibility for fabrication of Bi nanorods of high quality.

Synthesis of mono layer graphene oxide from sonicated graphite flakes and their Hall effect measurements

Siyar M, Maqsood A, Khan S B

Materials Science Poland

2014

Vol. 32, No. 2

292--296

Graphene, a single atom thick sheet is considered a key candidate for the future nanotechnology, due to its unique extraordinary properties. Researchers are trying to synthesize bulk graphene via chemical route from graphene oxide precursor. In the present work, we investigated a safe and efficient way of monolayer graphene oxide synthesis. To get a high degree of oxidation, we sonicated the graphite flakes before oxidation. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) results confirmed graphene oxide formation and high degree of oxidation. Raman spectroscopy and atomic force microscopy (AFM) results revealed a monolayer of graphene oxide (GO) flakes. The sheet like morphology of the GO flakes was further confirmed by scanning electron microscopy (SEM). The Hall effect measurements were performed on the GO film on a silica substrate to investigate its electrical properties. The results obtained, revealed that the GO film is perfectly insulating, having electrical resistivity up to 8.4 × 108 (W_cm) at room temperature.