Unforeseen high temperature and humidity stability of FeCl3_3 intercalated few layer graphene

We present the first systematic study of the stability of the structure and electrical properties of FeCl$_3$ intercalated few-layer graphene to high levels of humidity and high temperature. Complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and Raman spectroscopy conclusively demonstrate the unforeseen stability of this transparent conductor to a relative humidity up to $100 \%$ at room temperature for 25 days, to a temperature up to $150\,^\circ$C in atmosphere and up to a temperature as high as $620\,^\circ$C in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. The stability of FeCl$_3$ intercalated few-layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications.Comment: Scientific Reports, volume 5, article no. 760

Novel highly conductive and transparent graphene based conductors

Future wearable electronics, displays and photovoltaic devices rely on highly conductive, transparent and yet mechanically flexible materials. Nowadays indium tin oxide (ITO) is the most wide spread transparent conductor in optoelectronic applications, however the mechanical rigidity of this material limits its use for future flexible devices. Here we report novel transparent conductors based on few layer graphene (FLG) intercalated with ferric chloride (FeCl3) with an outstandingly high electrical conductivity and optical transparency. We show that upon intercalation a record low sheet resistance of 8.8 Ohm/square is attained together with an optical transmittance higher than 84% in the visible range. These parameters outperform the best values of ITO and of other carbon-based materials, making these novel transparent conductors the best candidates for future flexible optoelectronics

Is graphene a good transparent electrode for photovoltaics and display applications?

PublishedReviewThe current standard material used for transparent electrodes in displays, touch screens and solar cells is indium tin oxide (ITO) which has low sheet resistance (10 Ω/□), high optical transmission in the visible wavelength (85%) and does not suffer of optical haze. However, ITO is mechanically rigid and incompatible with future demands for flexible applications. Graphene materials share many of the properties desirable for flexible transparent conductors, including high optical transparency, high mechanical flexibility and strength. Whilst pristine graphene is not a good transparent conductor, functionalised graphene is at least 1000 times a better conductor than its pristine counterpart and it outperforms ITO. Here the authors review recent work on a novel graphene-based conductor with sheet resistance as low as 8.8 Ω/□ and 84% optical transmission. This material is obtained by ferric chloride (FeCl 3) intercalation into few-layer-graphene (FLG), giving rise to a new system which is the best known flexible and transparent electricity conductor. FeCl 3-FLG shows no significant changes in the electrical and structural properties for a long exposure to air, to high levels of humidity and at temperatures of up to 150°C in atmosphere. These properties position FeCl 3-FLG as a viable and attractive replacement to ITO.Engineering and Physical Sciences Research Council (EPSRC)Royal Society International Exchanges Schem

All-graphene photodetectors

notes: PMCID: PMC3694352Copyright © 2013 American Chemical Society.Published versionWe investigate the optoelectronic properties of novel graphene/FeCl3-intercalated few-layer graphene (FeCl3-FLG, dubbed graphexeter) heterostructures using photovoltage spectroscopy. We observe a prominent photovoltage signal generated at the graphene/FeCl3-FLG and graphene/Au interfaces, whereas the photovoltage at the FeCl3-FLG/Au interface is negligible. The sign of the photovoltage changes upon sweeping the chemical potential of the pristine graphene through the charge neutrality point, and we show that this is due to the photothermoelectric effect. Our results are a first step toward all-graphene-based photodetectors and photovoltaics.Engineering and Physical Sciences Research Council (EPSRC

Electron transport of WS2 transistors in a hexagonal boron nitride dielectric environment.

Open Access JournalCopyright: Freddie Withers, Thomas Hardisty Bointon, David Christopher Hudson, Monica Felicia Craciun & Saverio RussoWe present the first study of the intrinsic electrical properties of WS2 transistors fabricated with two different dielectric environments WS2 on SiO2 and WS2 on h-BN/SiO2, respectively. A comparative analysis of the electrical characteristics of multiple transistors fabricated from natural and synthetic WS2 with various thicknesses from single- up to four-layers and over a wide temperature range from 300 K down to 4.2 K shows that disorder intrinsic to WS2 is currently the limiting factor of the electrical properties of this material. These results shed light on the role played by extrinsic factors such as charge traps in the oxide dielectric thought to be the cause for the commonly observed small values of charge carrier mobility in transition metal dichalcogenides.EPSRCRoyal Society Travel Exchange Gran

Unforeseen high temperature and humidity stability of FeCl3 intercalated few layer graphene

This is the final version of the article. Available from the publisher via the DOI in this record.We present the first systematic study of the stability of the structure and electrical properties of FeCl3 intercalated few-layer graphene to high levels of humidity and high temperature. Complementary experimental techniques such as electrical transport, high resolution transmission electron microscopy and Raman spectroscopy conclusively demonstrate the unforseen stability of this transparent conductor to a relative humidity up to 100% at room temperature for 25 days, to a temperature up to 150°C in atmosphere and to a temperature as high as 620°C in vacuum, that is more than twice higher than the temperature at which the intercalation is conducted. The stability of FeCl3 intercalated few-layer graphene together with its unique values of low square resistance and high optical transparency, makes this material an attractive transparent conductor in future flexible electronic applications

The effects of vibration on fringe projection systems

Mechanical vibration noise is a significant source of error in precision measuring instruments. Errors due to vibration can be detected in measurement signals, and so methods to control mechanical vibration must be considered throughout the design process. Fringe projection (FP) is a fast, non-contact and non-destructive measurement technology, that allows for the rapid form measurement of engineering components. There is an increasing demand in industry for low-intervention, factory-friendly FP systems. Vibration is reported to be a significant source of mechanical error in FP measurements, and so in order to design an effective metrology solution, it is vital to first understand the FP systems’ sensitivity to vibrational noise. In this research, a methodology for assessing the effects of vibration on the measurement accuracy and repeatability of a low-cost FP system is presented. The research includes a theoretical investigation of the effects of vibration on FP measurements using a computational simulation technique, as well as an experimental study, which is compared with the simulated results. The methodology presented here allows for the rapid benchmarking of a given FP system operating in any configuration, and can be used to define the required vibrational performance parameters of the system

Large-area functionalized CVD graphene for work function matched transparent electrodes

PublishedArticleThe efficiency of flexible photovoltaic and organic light emitting devices is heavily dependent on the availability of flexible and transparent conductors with at least a similar workfunction to that of Indium Tin Oxide. Here we present the first study of the work function of large area (up to 9 cm2) FeCl3 intercalated graphene grown by chemical vapour deposition on Nickel, and demonstrate values as large as 5.1 eV. Upon intercalation, a charge density per graphene layer of 5 ⋅ 1013 ± 5 ⋅ 1012 cm−2 is attained, making this material an attractive platform for the study of plasmonic excitations in the infrared wavelength spectrum of interest to the telecommunication industry. Finally, we demonstrate the potential of this material for flexible electronics in a transparent circuit on a polyethylene naphthalate substrate.EPSRCRoyal Society international Exchanges Schem

Light and smell stimulus protocol reduced negative frontal EEG asymmetry and improved mood

Light and smell have both been shown to induce beneficial changes to human psychophysiology. Bright light therapy has been shown to have a positive impact on anxiety and depression and smell has also been shown to have positive effects on mood, stress, anxiety and depression. We developed a method for the delivery of integrated light and smell stimulation to try to optimise positive psychophysiological benefit. We tested its effectiveness on a physiological measure, EEG frontal alpha asymmetry (FA) and a psychological paradigm, the POMS test, both of which have been used as a measure of emotional state and mood. Light, pleasant smell, combined light+smell and a no stimulus control were delivered for 90s while the frontal alpha asymmetry (FA) was monitored. Smell and light+smell caused significant reductions in negative FA during stimulation. Exposure to a longer 15 min nonadaptive light+smell stimulus protocol reduced negative FA and decreased negative affect (POMS). The effects were greater in the negative FA group. Both the physiological (EEG) and psychometric (POMS) data indicate that integrated light and smell stimulation can reduce negative affect and reduce a marker for anxiety/ depression. This light+smell sensory stimulation protocol could offer a safe treatment for depression/anxiety