High-Performance Flexible Graphene Field Effect Transistors with Ion Gel Gate Dielectrics

Abstract

A high-performance low-voltage graphene field-effect transistor (FET) array was fabricated on a flexible polymer substrate using solution-processable, high-capacitance ion gel gate dielectrics. The high capacitance of the ion gel, which originated from the formation of an electric double layer under the application of a gate voltage, yielded a high on-current and low voltage operation below 3 V. The graphene FETs fabricated on the plastic substrates showed a hole and electron mobility of 203 ( 57 and 91 ( 50 cm 2 /(V · s), respectively, at a drain bias of -1 V. Moreover, ion gel gated graphene FETs on the plastic substrates exhibited remarkably good mechanical flexibility. This method represents a significant step in the application of graphene to flexible and stretchable electronics.KEYWORDS Graphene, ion gel, flexible electronics, field effect transistor, low-voltage operation G raphene has attracted attention for a range of electronic applications, such as displays, solar cells, and sensors owing to its exceptional electronic and optoelectronic properties. [1][2][3][4] Recent developments in the large area synthesis of high-quality graphene films has created new pathways for the application of graphene to highfrequency devices. [5][6][7] There are two general approaches for fabricating graphene devices over large areas: one that employs graphene grown directly on SiC wafers 8 and another that transfers graphene films synthesized on metal layers to other useful substrates. 9,10 The latter approach is attractive because of the special attributes of graphene films, such as flexible/stretchable device fabrication and the possibility of fabrication over large areas. This approach has produced device arrays on rigid insulating wafers and is scalable to a wafer size. 9 Although several studies have reported graphene field-effect transistors (FETs) on a plastic substrate, 11 there are still significant challenges in fabricating large scale, flexible graphene FETs.Exploring graphene for flexible electronics requires solution-processable, high-capacitance gate dielectrics that can form at low temperature with a good interface with the graphene films transferred to plastic sheets. Although several high-k inorganic dielectrics, such as HfO 2 , Al 2 O 3 , and ZrO 2 , have been applied to the fabrication of graphene FETs, they cannot be available for flexible devices based on plastic substrates due to their high growth temperature. 8,12,13 This paper reports a promising method for fabricating a low-voltage operating graphene FET array on plastic substrates using an ion gel as the gate dielectric. The ion gel consists of a room temperature ionic liquid and gelating triblock copolymer, which exhibits an extremely high capacitance of 5.17 µF/cm 2 . [14][15][16] The high capacitance of the ion gel gate dielectrics in the graphene FETs provides both high on-current and low voltage operation. Furthermore, ion gel gated graphene FETs fabricated on plastic substrates show very good mechanical flexibility.Before the fabric...

Characterization of Al2O3 gate dielectric for graphene electronics on flexible substrates

“…Graphene-based field effect transistors (GFETs) are one of the primary components used in electronic circuits, which have developed rapidly in recent years [3]. In particular, GFETs have great potential for flexible and stretchable devices due to their excellent mechanical flexibility [4], opening up a variety of promising applications in flexible electronics [5]. To ensure the high performance of GFETs on flexible substrates, an uniform and manufacturable dielectric film is needed for efficient charge injection into the graphene channel [6] and direct reduction of impurity scattering at the dielectric/graphene interface [7].…”

Electrical performance of monolayer MoS2 field-effect transistors prepared by chemical vapor deposition

“…5 Furthermore, MoS 2 also shows promise for use in logic circuits and optoelectronic devices, and it is a promising material for use on flexible and transparent substrates. 7,8 The vast majority of recent reports on MoS 2 , like the early literature on graphene, are based on samples prepared by mechanical exfoliation. 2 While there have been several reports on monolayer MoS 2 devices, many of these studies utilize few-layer (2-5) MoS 2 , since its exfoliation typically results in flakes with significantly greater thickness and smaller size than what can be readily obtained for graphene.…”

Conductance modulation in topological insulator Bi2Se3 thin films with ionic liquid gating

“…Among the TIs discovered so far, Bi 2 Se 3 is considered as one of the most promising TI materials with its well defined single Dirac cone and a larger bulk bandgap of 0.3 eV compared to that of 0.14 eV in Bi 2 Te 3 . 7 Moreover, considering that prototypes of a field effect transistor (FET) device have been fabricated with graphene by taking advantage of the massless behaviors of carriers, 8,9 TIs can be another suitable material for FET applications.…”

“…19 In analogy to the optical properties of graphene, a thin TI film has been predicted to be transparent and conductive for optoelectronic applications such as displays, organic lightemitting diodes (OLEDs), and touch screens. 8,20 The transparency of thin Bi 2 Se 3 films was investigated using ultraviolet-visible-infrared (UV-VIS-IR) spectroscopy. Figure 1(a) shows that the net transmittance of the Bi 2 Se 3 films decreases as the film becomes thicker.…”