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Lateral manipulation of fullerenes on clean silicon surfaces may be induced by either an attractive or repulsive interaction between adsorbed molecules and the tip of a scanning probe microscope, and can result in a complex response arising from molecular rolling. The model for rolling is supported by new results which show that manipulation is suppressed for adsorbed functionalized fullerenes due to the presence of phenyl sidegroups. The influence of varying the dwell time of the tip during manipulation is also reported. By reducing this time to a value which is less than the response time of the feedback control loop it is possible to induce manipulation in a quasi-constant height mode which is accompanied by large increases/decreases in current.

The chromatographic procedure which led to isolation of the first pure samples of C₆₀ and C₇₀, together with recent advances in the separation of higher fullerenes, are described. At least three isomers of C₇₈ exist. Structural features contributing to the stability differences between fullerenes are discussed. ¹³C NMR, UV, IR, Raman and neutron scattering/diffraction measurements on C₆₀ and C₇₀ are summarized and reviewed.

We reply to the comment made by Sassara A et al 1997 ( J. Phys. B: At. Mol. Opt. Phys. 30 4415 - 6) and agree with their conclusions.

Although it is some five years since fullerenes were extracted in macroscopic quantities from the black, superficially amorphous sooty deposits produced by a carbon arc under helium, little is known in detail about the structure of the deposit or its electrical and magnetic properties. Here we provide evidence that this deposit, known as fullerene soot, is composed of defective networks of carbon atoms which do not have all valencies satisfied. We have studied these soots, before and after thermal annealing, using x-ray and electron diffraction, electron spin-resonance (ESR) spectroscopy, infra-red transmission and measurements of electrical conductivity. We find that localized states associated with such dangling bonds are removed from the soot on annealing and this process is accompanied by an ordering transition which modifies the electrical and magnetic properties. The fullerene soot particles appear to be encapsulated aggregates of highly defective carbon `onions'. Such metastable defective networks undergo a subtle ordering processes upon heat treatment which is accompanied by a rise in the electrical conductivity and a loss of paramagnetism due to the elimination of unsatisfied carbon atom valencies. Electrical conductivity and infra-red transmission measurements indicate that the centre of these `onions' is graphitic, with metallic properties. The temperature dependence of the electrical conductivity suggests that charge transport in both annealed and unannealed materials occurs by tunnelling between metallic islands in the sample. The ESR linewidth, arising from the spin centres in fullerene soots, is not significantly changed by exposure to oxygen. This suggests that the free radical centres in fullerene soots are extremely efficiently isolated from the atmosphere - presumably by encapsulation. This behaviour contrasts with that of amorphous carbons prepared by thermal decomposition of organic materials (chars). The ESR g-factors of the fullerene soots are lower than those of chars, which suggests that the radicals in fullerene soots have strong sigma character due to unsatisfied -type valencies. In this paper, a plausible structure and associated annealing mechanism for the fullerene soot is presented based on these experimental observations.

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Due to an oversight, the captions for figures 1 and 2 were transposed. The correct figure captions are given below.

Figure 1. A transmission electron micrograph of 50 Torr He fullerene soot showing coagulated balloons which are suggested to be sealed containers of defective free radical material. Notice that the shape of the particles suggests that the balloons contain several structures held together initially by Van der Waals forces and then sealed by a number of coats of carbon atoms in the gas phase.

Figure 2. Small-aperture transmission electron diffraction of 50 Torr He soot. The spot pattern shown is consistent with a collection of randomly orientated graphitic microcrystallites as shown in figure 3.

Almost exactly five years after C₆₀ Buckminsterfullerene was discovered serendipitously during a series of graphite laser vaporization experiments which were designed to simulate the chemistry in a red giant carbon star, the molecule has been isolated in macroscopic amounts. This breakthrough has triggered an explosion of research into its chemical and physical properties. The molecule has already exhibited a wide range of novel phenomena which promise exciting applications. The discovery also has important implications for the nucleation pathways and structure-governing processes involved in the formation of carbon microparticles. The factors that led to the discovery of the molecule as well as elucidation of the structure are discussed as are the astrophysical and terrestrial implications of the recent advances.

We have performed a transmission electron microscopical study of samples where pure Ge has been grown on differently oriented Si wafers by reduced pressure chemical vapour deposition. In the present study we examine pure Ge layers grown on (111)Si wafers by annular dark-field (ADF) scanning transmission electron microscopy (STEM) and by high-resolution electron microscopy (HREM). There is evidence of immediate strain relaxation taking place by dislocations and twinning. A novel configuration of micro-twins has been observed at the interface between the pure Ge and the underlying (111)Si wafer. Growth mechanisms and models to explain the interfacial configurations of this type of wafer are suggested.

In this report we demonstrate the successful 80kV alignment of a double aberration corrected TEM/STEM (JEM-Z3100F-R005) equipped with a cold field emission gun designed to operate at 300kV. In TEM mode we demonstrate information transfer out to 0.078nm in the corresponding power spectrum. For high angle annular dark-field STEM, direct resolution of the 0.082nm Ge (444) dumbbells was achieved. The energy spread of the primary electron beam was studied using energy-loss spectroscopy. Reduction of the extraction anode voltage (A1) to 1.2kV results in an energy resolution in the primary electron beam, taken as the full width half maximum (FWHM) of the zero loss peak, of 0.28eV with a corresponding beam current of 12pA whereas operation of A1 at 1.5kV results in a FWHM at the zero-loss peak of ∼0.4eV for a beam current of 1.1nA.

This work presents an investigation of the thickness, the chemical composition and the band-gap properties of AlGaN/GaN quantum wells grown by Metal-Organic Chemical Vapour Deposition (MOCVD) on sapphire (0001) substrates. Various methods of analysis by transmission electron microscopy (TEM) were used for the characterization of these layers, such as scanning transmission electron microscopy STEM, energy-dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). Annular dark-field STEM provides more accurate layer thicknesses and Al concentrations than EDXS profiling.

A combination of molecular beam epitaxy (MBE) and atomic layer deposition (ALD) was adopted to fabricate GaN-based core/shell NW structures. ALD was used to deposit a HfO₂ shell of onto the MBE grown GaN NWs. Electron transparent samples were prepared by focussed ion beam methods and characterized using state-of-the-art analytical transmission and scanning transmission electron microscopy. The polycrystalline coating was found to be uniform along the whole length of the NWs. Photoluminescence and Raman spectroscopy analysis confirms that the HfO₂ ALD coating does not add any structural defect when deposited on the NWs.