Periodic ripples on thermally-annealed Graphene on Cu (110) – reconstruction or Moiré pattern?

We have used Ultrahigh Vacuum (UHV) Scanning tunneling microscopy (STM) to investigate the effect of thermal annealing of graphene grown by chemical vapor deposition (CVD) on a Cu(110) foil. We show that the annealing appears to induce a reconstruction of the Cu surface along the [210] direction, with a period of 1.43 nm. Such reconstructions have been ascribed to the tensile strain induced in the Cu surface by its differential thermal expansion relative to the graphene over-layer, but we show that it is in fact a Moiré pattern due to interference between the graphene and the underlying atomic lattice as evidenced by the appearance of an odd-even transition only observed due to mis-orientation of the top layer of a layered crystal. This highlights that the analysis of STM measurements of graphene on metal surfaces should take such interference effects into account and that the graphene-Cu interface is more complex than previously thought

Nanometre-scale investigations by atomic force microscopy into the effect of different treatments on the surface structure of hair.

OBJECTIVE: To investigate the effect of different washing regimes on the surface of human hair at the nanometre scale - comparable to the size of typical deposits left behind by commercial products. METHODS: Atomic force microscopy (AFM) and related techniques. RESULTS: It can be directly seen that washing hair using commercial hair care products removes deposits that naturally form on the shaft, revealing the underlying structure of the hair, whereas in many cases leaving new deposits behind. The spatial distribution of these deposits is explored and quantified. The spatial distribution of the surface charge of pristine hair is mapped, and the electrical screening effect of deposits is directly observed. We also show that the roughness of the treated hair depends directly on the type of product used, with a marked difference between shampoo and conditioner. Some products leave isolated deposits behind, whereas others leave layers of material behind which wet the hair surface. CONCLUSION: Atomic force microscopy and the related techniques we have employed in a forensic approach is able to distinguish between different hair care products on the basis of the deposits they leave behind. This opens up the capability of further analysis tools to complement already existing techniques.This is the accepted manuscript version. The final version is available from Wiley at http://dx.doi.org/10.1111/ics.12161

Towards reproducible, scalable lateral molecular electronic devices

An approach to reproducibly fabricate molecular electronic devices is presented. Lateral nanometer-scale gaps with high yield are formed in Au/Pd nanowires by a combination of electromigration and Joule-heating-induced thermomechanical stress. The resulting nanogap devices are used to measure the electrical properties of small numbers of two different molecular species with different end-groups, namely 1,4-butane dithiol and 1,5-diamino-2-methylpentane. Fluctuations in the current reveal that in the case of the dithiol molecule devices, individual molecules conduct intermittently, with the fluctuations becoming more pronounced at larger biases.This is the author's accepted manuscript. Copyright (2014) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters and may be found at http://scitation.aip.org/content/aip/journal/apl/105/8/10.1063/1.4894091

Nanometer-Scale Investigations into Oil-Rich Chalk Formations

Core samples from two different depths of a Carbonate oil field have been investigated using optical and electron microscopy, elemental mapping and atomic force microscopy. The sample from the greater depth displays a striking magnetic response, greater compaction and cementation of coccoliths, and an oily film on all surfaces, whereas the sample from higher up shows no magnetic response, no oily film and less well-developed coccoliths. Our results reveal the link between oil formation and the presence of iron compounds.This work was carried out under the NanoOil project, funded by BP.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acs.energyfuels.5b0093

Vibrational coherence in electron spin resonance in nanoscale oscillators

We study a scheme for electrical detection, using electron spin resonance, of coherent vibrations in a molecular single electron level trapped near a conduction channel. Both equilibrium spin-currents and non-equilibrium spin- and charge currents are investigated. Inelastic side-band anti-resonances corresponding to the vibrational modes appear in the electron spin resonance spectrum.Comment: 4 pages, 3 figures: Published versio

On the Manipulation of Ferroelectric and Ferroelastic Domains at the Nanoscale

The distribution and evolution of ferroelectric and ferroelastic nanodomains in a polycrystalline (001)-oriented thin film of the simple multi-ferroic PbZr0.3Ti0.7O3(PZT) is presented. With an external electric field applied between the probe tip and the PZT sample, ferroelastic domains were switched by rotating both in- and out-of-plane, with a partial conversion from a-oriented regions to c-oriented regions. After multiple such cycles, grains were observed to buckle as a direct consequence of the lateral size change arising from the conversion towards complete c-orientation. The factors determining the measured deflection of the cantilever in Piezoresponse force microscopy were explored, highlighting the conditions under which quantitative or qualitative information may be obtained.This is the accepted manuscript. The final version is available from Springer at http://link.springer.com/article/10.1007%2Fs11664-015-3674-z

Characterisation of carbonaceous deposition in oil exposed surfaces at the nanoscale

© 2016 IEEE. Carbonaceous deposits in oil exposed surfaces are responsible for compromising performance and reducing profitability across the hydrocarbons value chain. In particular, in upstream operation, fouling between the well and the production facility has been found to reduce flow, availability and reliability resulting in lost production. Thus, a better understanding of the processes leading to the deposition of these complex and heavy organic compounds is required, since it is unclear whether they primarily aggregate in the liquid phase or at the liquid-solid interface. In an effort to understand the mechanisms behind deposition, this study uses different modalities of atomic force microscopy (AFM) to characterise relevant metallic, oil exposed surfaces with deposits already on them. More specifically, in this post-mortem analysis, surfaces exposed to oil with and without the presence of an inhibitor are imaged in an effort to pinpoint the effect of the inhibitor on deposition

Evaluating femtosecond laser ablation of graphene on SiO<inf>2</inf>/Si substrate

We demonstrate a uniform single layer micropattern of graphene on 300 nm thick SiO2 on a Si substrate using a 1030 nm, 280 fs laser. The cutting process was conducted in air, the pattern defined through the motion of a high-precision translation stage. Approximately 1.6 μm wide graphene microchannels were cut with uniform widths and well defined edges. The ablation threshold of graphene was determined to be 66–120 mJ/cm2, at which the selective removal of graphene was achieved without damage to the SiO2/Si substrate. Scanning electron microscopy images revealed high quality cuts (standard deviation 40 nm) with little damage or re-deposition. Raman maps showed no discernible laser induced damage in the graphene within the ablation zone. Atomic force microscopy revealed an edge step height ranging from less than 2 to 10 nm, suggesting little removal of SiO2 and no damage to the silicon (the central path showed sub ablation threshold swelling). The effect of the ultrafast laser on the surface potential at the cut edge has been measured and it showed a distinguishable boundary.This work was supported by The Engineering and Physical Sciences Research Council (EPSRC) and National University of Defence Technology (NUDT). The authors also thank Cambridge Graphene Centre (CGC).This is the final version of the article. It first appeared from the American Institute of Physics via http://dx.doi.org/10.2351/1.494451

Noise spectroscopy and interlayer phase-coherence in bilayer quantum Hall systems

Bilayer quantum Hall systems develop strong interlayer phase-coherence when the distance between layers is comparable to the typical distance between electrons within a layer. The phase-coherent state has until now been investigated primarily via transport measurements. We argue here that interlayer current and charge-imbalance noise studies in these systems will be able to address some of the key experimental questions. We show that the characteristic frequency of current-noise is that of the zero wavevector collective mode, which is sensitive to the degree of order in the system. Local electric potential noise measured in a plane above the bilayer system on the other hand is sensitive to finite-wavevector collective modes and hence to the soft-magnetoroton picture of the order-disorder phase transition.Comment: 5 pages, 2 figure

Temperature dependence of the ohmic conductivity and activation energy of Pb1+y(Zr0.3Ti0.7)O3 thin films

The ohmic conductivity of the sol-gel derived Pb1+y(Zr0.3Ti0.7)O3 thin films (with the excess lead y=0.0 to 0.4) are investigated using low frequency small signal alternate current (AC) and direct current (DC) methods. Its temperature dependence shows two activation energies of 0.26 and 0.12 eV depending on temperature range and excess Pb levels. The former is associated with Pb3+ acceptor centers, while the latter could be due to a different defect level yet to be identified.Comment: 13 pages, 3 figures, PostScript. Submitted to Applied Physics Letter