Considerable Enhancement of Field Emission of SnO2Nanowires by Post-Annealing Process in Oxygen at High Temperature

The field emission properties of SnO2nanowires fabricated by chemical vapor deposition with metallic catalyst-assistance were investigated. For the as-fabricated SnO2nanowires, the turn-on and threshold field were 4.03 and 5.4 V/μm, respectively. Considerable enhancement of field emission of SnO2nanowires was obtained by a post-annealing process in oxygen at high temperature. When the SnO2nanowires were post-annealed at 1,000 °C in oxygen, the turn-on and threshold field were decreased to 3.77 and 4.4 V/μm, respectively, and the current density was increased to 6.58 from 0.3 mA/cm2at the same applied electric field of 5.0 V/μm

Effect of Topological Defects on Buckling Behavior of Single-walled Carbon Nanotube

Molecular dynamic simulation method has been employed to consider the critical buckling force, pressure, and strain of pristine and defected single-walled carbon nanotube (SWCNT) under axial compression. Effects of length, radius, chirality, Stone–Wales (SW) defect, and single vacancy (SV) defect on buckling behavior of SWCNTs have been studied. Obtained results indicate that axial stability of SWCNT reduces significantly due to topological defects. Critical buckling strain is more susceptible to defects than critical buckling force. Both SW and SV defects decrease the buckling mode of SWCNT. Comparative approach of this study leads to more reliable design of nanostructures

Hall Measurements on Carbon Nanotube Paper Modified With Electroless Deposited Platinum

Carbon nanotube paper, sometimes referred to as bucky paper, is a random arrangement of carbon nanotubes meshed into a single robust structure, which can be manipulated with relative ease. Multi-walled carbon nanotubes were used to make the nanotube paper, and were subsequently modified with platinum using an electroless deposition method based on substrate enhanced electroless deposition. This involves the use of a sacrificial metal substrate that undergoes electro-dissolution while the platinum metal deposits out of solution onto the nanotube paper via a galvanic displacement reaction. The samples were characterized using SEM/EDS, and Hall-effect measurements. The SEM/EDS analysis clearly revealed deposits of platinum (Pt) distributed over the nanotube paper surface, and the qualitative elemental analysis revealed co-deposition of other elements from the metal substrates used. When stainless steel was used as sacrificial metal a large degree of Pt contamination with various other metals was observed. Whereas when pure sacrificial metals were used bimetallic Pt clusters resulted. The co-deposition of a bimetallic system upon carbon nanotubes was a function of the metal type and the time of exposure. Hall-effect measurements revealed some interesting fluctuations in sheet carrier density and the dominant carrier switched from N- to P-type when Pt was deposited onto the nanotube paper. Perspectives on the use of the nanotube paper as a replacement to traditional carbon cloth in water electrolysis systems are also discussed

Effect of Substrate Morphology on Growth and Field Emission Properties of Carbon Nanotube Films

Carbon nanotube (CNT) films were grown by microwave plasma-enhanced chemical vapor deposition process on four types of Si substrates: (i) mirror polished, (ii) catalyst patterned, (iii) mechanically polished having pits of varying size and shape, and (iv) electrochemically etched. Iron thin film was used as catalytic material and acetylene and ammonia as the precursors. Morphological and structural characteristics of the films were investigated by scanning and transmission electron microscopes, respectively. CNT films of different morphology such as vertically aligned, randomly oriented flowers, or honey-comb like, depending on the morphology of the Si substrates, were obtained. CNTs had sharp tip and bamboo-like internal structure irrespective of growth morphology of the films. Comparative field emission measurements showed that patterned CNT films and that with randomly oriented morphology had superior emission characteristics with threshold field as low as ~2.0 V/μm. The defective (bamboo-structure) structures of CNTs have been suggested for the enhanced emission performance of randomly oriented nanotube samples