Showing papers by "S. Roth published in 1999"
TL;DR: In this article, the authors measured the pressure dependence of the high-energy Raman modes in single and multi-walled carbon nanotubes and found the pressure coefficient to be linear in both materials but 25% smaller in MWNT.
Abstract: The pressure dependence of the high-energy Raman modes in single- and multi-walled carbon nanotubes was measured in the range 0–10 GPa. We found the pressure coefficient to be linear in both materials but 25% smaller in MWNT. Given that the curvature effects on vibrational properties of the rolled-up graphene sheets are small, we can explain this difference simply with elasticity theory.
86 citations
TL;DR: In this paper, size exclusion chromatography (SEC) is applied to surfactant stabilised dispersions of raw material produced in a Kraetschmer generator to remove carbon nanospheres, metal particles and amorphous carbon.
85 citations
Journal Article•
TL;DR: In this paper, the authors measured the pressure dependence of the high-energy Raman modes in single and multi-walled carbon nanotubes in the range 0-10 GPa and found the pressure coefficient to be linear in both materials but 25% smaller in MWNT.
Abstract: The pressure dependence of the high-energy Raman modes in single- and multi-walled carbon nanotubes was measured in the range 0-10 GPa. We found the pressure coefficient to be linear in both materials but 25% smaller in MWNT. Given that the curvature effects on vibrational properties of the rolled-up graphene sheets are small, we can explain this difference simply with elasticity theory.
78 citations
TL;DR: In this article, the radial breathing and C-C stretching modes of single-wall carbon nanotubes (SWNTs) were investigated with a Raman microscope, each with a distinct sharp peak in radial breathing mode area.
77 citations
TL;DR: In this article, the authors suggest that conduction in carbon nanotube ropes or mats is best understood in terms of a heterogeneous model, involving regions of metallic conduction together with hopping or tunnelling through small electrical barriers corresponding to defects of various types.
64 citations
TL;DR: In this article, the adsorption of carbon SWNTs from purified aqueous dispersions on electrode patterns is described, where gold particles are attached to SWNT ropes after chemical tube modification by a two-step oxidation process.
27 citations
TL;DR: In this paper, structural analysis of the cross section of gold/Langmuir-Blodgett (LB) polymer film/gold sandwich structures was performed using transmission electron microscopy (TEM), and the obtained results were complemented by electron transport investigations of the sandwich structures.
Abstract: Structural analysis of the cross section of gold/Langmuir-Blodgett (LB) polymer film/gold sandwich structures was performed using transmission electron microscopy (TEM), and the obtained results were complemented by electron transport investigations of the sandwich structures. The polymer film consisted of four to ten LB monolayers of a nonconducting polymer. TEM analysis of the sandwich cross section revealed a number of gold particles, 2–5 nm in size, formed during the fabrication process within the LB film close to the top electrode. Low temperature dc-transport measurements showed current-voltage (I-V) characteristics with equidistant steps that are not expected if the polymer film is thought to form a single laterally extended tunneling barrier between the metal electrodes. This feature can be understood, however, on the basis of the Coulomb blockade model applied to cluster-like metallic inclusions acting as an island separated from both Au electrodes by tunneling barriers.
24 citations
TL;DR: In this article, the four-probe conductivity and magnetoresistance in micron-scale polyacetylene (PA) fiber networks were measured and a remarkably weaker temperature dependence of resistivity compared to that of the bulk PA film was observed.
18 citations
TL;DR: In this article, the authors measured the electrical resistivity and thermoelectric power of single wall carbon nanotube (SWCN) network and fitted the resistivity result to the variable range hopping (VRH) type conduction formula.
13 citations
TL;DR: In this paper, a review of the application of scanning force microscopy in nanotube science is presented, where the non-destructive character of this technique allows the structural characterisation of (chemically modified) single and multi-wall nanotubes deposited on substrates for further investigations such as electrical transport measurements.
Abstract: Recent developments in the application of scanning force microscopy in nanotube science are reviewed. The non-destructive character of this technique allows the structural characterisation of (chemically modified) single- and multi-wall nanotubes deposited on substrates for further investigations such as electrical transport measurements. Furthermore, SFM is now an established tool for manipulation of nanotubes, which allows position control and determination of elastic constants such as the Young’s modulus. Finally it is shown that very sharp and stable probes for scanning force microscopy can be made from nanotubes due to their excellent stability and aspect ratio.
12 citations
01 Jan 1999
TL;DR: In this paper, the temperature dependence of the resistivity of the entangled single wall carbon nanotube (SWCN) network is studied, showing that the negative dρ/dT from T=4.2K to 300K fits well to the 2-dimensional variable range hopping (VRH) (ρ(T)=ρ 0 exp((T 0 /T) 1/3 )) formula with T 0 = 259.2 K.