A new Raman metric for the characterisation of graphene oxide and its derivatives

Raman spectroscopy is among the primary techniques for the characterisation of graphene materials, as it provides insights into the quality of measured graphenes including their structure and conductivity as well as the presence of dopants. However, our ability to draw conclusions based on such spectra is limited by a lack of understanding regarding the origins of the peaks. Consequently, traditional characterisation techniques, which estimate the quality of the graphene material using the intensity ratio between the D and the G peaks, are unreliable for both GO and rGO. Herein we reanalyse the Raman spectra of graphenes and show that traditional methods rely upon an apparent G peak which is in fact a superposition of the G and D’ peaks. We use this understanding to develop a new Raman characterisation method for graphenes that considers the D’ peak by using its overtone the 2D’. We demonstrate the superiority and consistency of this method for calculating the oxygen content of graphenes, and use the relationship between the D’ peak and graphene quality to define three regimes. This has important implications for purification techniques because, once GO is reduced beyond a critical threshold, further reduction offers limited gain in conductivity

Complementary circuits based on solution processed low-voltage organic field-effect transistors

The field of organic electronics is advancing quickly towards ultra low-cost, low-end applications and is expected to provide the necessary technology required for flexible/printed electronics. Here we address the need for solution processed low-voltage complementary logic in order to reduce power consumption of organic circuits and hence enable their use in portable, i.e. battery-powered applications. We demonstrate both p- and n-channel solution processed high performance organic field-effect transistors that operate at voltages below |1.5| V. The reduction in operating voltage is achieved by implementing ultra-thin gate dielectrics based on solution processed self-assembled monolayers. This work demonstrates the feasibility of fabricating low-voltage complementary organic circuits by means of solution processing. © 2009 Elsevier B.V. All rights reserved

Fluorine containing C(60) derivatives for high-performance electron transporting field-effect transistors and integrated circuits

We report on electron transporting organic transistors and integrated ring oscillators based on four different solution processible fluorine containing C60 derivatives. Electron mobilities up to 0.15 cm2 V s are obtained from as-prepared bottom-gate, bottom-contact transistors utilizing gold source-drain electrodes. Despite the high mobility, no long-range structural order could be identified with the semiconductor films exhibiting amorphouslike characteristics. The good electron transport is attributed to the structural symmetry of the fullerene derivatives and the enhanced π -π interactions between C60 units even in the case of amorphouslike films. These advantageous characteristics make fluorine containing C60 derivatives attractive for application in high-performance, large-area organic electronics. © 2008 American Institute of Physics