Electric field effect in graphite crystallites

Abstract

Graphite is a highly anisotropic crystal with a quasi-two-dimensional electronic structure exhibiting high intrinsic charge carrier mobility. Here, we investigate the effect of an electric field on the resistance of individual graphite crystallites with a thickness on the order of 40 nm. Ambipolar field-effect behavior was achieved with the aid of a polymer electrolyte gate. By optimizing the device geometry, devices with an on/off current ratio of up to 4 and carrier mobilities of around 100 cm2/Vs could be attained directly on the crystallites.

Field effect transistors and RC filters from pencil-trace on paper

“…This would be expected given that the substrate (paper) is rough and that non-uniformity of pencil traces may cause variation in the mobility values. The mobility values are less compared to the literature values obtained with graphite crystallites on SiO 2 surface, 20 but are much higher compared to reduced graphene oxide based FETs. 34 However, the simple device reported here is not to be compared in terms of reproducible behavior and performance with a well-controlled single layer graphene device for example.…”

“…The electric field effect is less in the case of HOPG trace, which may be due to higher screening effects. 20 The pencil trace being turbostratic in nature with the intercalated clay particles, behaves like a 2D graphite system which is revealed through the observation of significant electric field effect induced by the gate. The flexibility of the ion gel dielectric is demonstrated in Fig.…”

“…4b) reflected the ambipolar nature where the positive and negative regions of gate voltage represent electron and hole transport, respectively. 20 The asymmetry in the transfer curve indicates that the hole and electron mobilities are not equal. This may be attributed to the unintentional doping of pencil marks by water molecules through capillaries of the paper which may suppress the electron mobility.…”

“…22 The Dirac point minimum is shifted from 0 V, which may be due to local disorder arising from the intermixed clay particles and also the defects between the adjacent layers. 20 The broad Dirac point minimum in the transfer curve can be attributed to the deriving of electric field effect from multilayers of graphene in the pencil trace. 33 The gate leakage current (see Fig.…”

“…13 On the other hand, inorganic based dielectrics, which require high growth temperatures 19 but suffer from lower gate coupling efficiency, may not be suitable for fabricating FETs on paper substrates. 20 To be compatible with paper, the dielectric has to be deposited near ambient conditions yet possessing a high gate capacitance. Ionic liquids such as 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMITFSI], readily form electrochemical double layers (EDLs) and possess high thermal stability, non-volatility and high ion conductivity at room temperature (B0.02 S cm À1 ), and therefore are used as dielectric medium for low voltage operation of FETs.…”