Charge transport mechanisms in inkjet-printed thin-film transistors based on two-dimensional materials

Abstract

Printed electronics has emerged as a pathway for large scale, flexible, and wearable devices enabled by graphene and two-dimensional (2D) materials. Solution processing of graphite and layered materials demonstrated mass production of inks allowing techniques such as inkjet printing to be used for device fabrication. However, the complexity of the ink formulations and the polycrystalline nature of the thin films, together with the metal, semimetal, and semiconducting behaviour of different 2D materials, have impeded the investigation of charge transport in inkjet printed 2D material devices. Here we unveil the charge transport mechanisms of surfactant-and solvent-free inkjet-printed thin-film devices of representative few-layer graphene (semi-metal), molybdenum disulfide (MoS2, semiconductor) and titanium carbide MXene (Ti3C2, metal) by investigating the temperature (T ), gate and magnetic field dependencies of their electrical conductivity. We find that charge transport in printed few-layer MXene and MoS2 devices is dominated by the intrinsic transport mechanism of the constituent flakes: MXene devices exhibit a weakly-localized 2D metallic behavior at any T , whereas MoS2 devices behave as insulators with a crossover from 3D-Mott variable-range hopping at low T to nearest-neighbor hopping around at ∼ 200 K. The charge transport in printed few-layer graphene devices is dominated by the transport mechanism between different flakes, which exhibit 3D-Mott variable range hopping conduction at any T . These findings reveal and finally establish the fundamental mechanisms responsible for charge transport in inkjet-printed devices with 2D materials, paving the way for a reliable design of high performance printed electronics.

Anomalous Metallic Phase in Molybdenum Disulphide Induced via Gate-Driven Organic Ion Intercalation

“…Figure 5 a shows the T -dependence of , divided by its value at K (shown in Figure 1 c), down to T ∼3 K and for a series of MoS crystals with increasing release times. The pristine MoS crystal shows the exponentially-increasing with decreasing T typical of insulators where conduction occurs via hopping processes in the localized states in the band tails, as expected [ 48 , 69 ].…”

“…Figure 5a shows the T -dependence of ρ, divided by its value at T = 300 K (shown in Figure 1c), down to T ∼ 3 K and for a series of MoS 2 crystals with increasing release times. The pristine MoS 2 crystal shows the exponentially-increasing ρ with decreasing T typical of insulators where conduction occurs via hopping processes in the localized states in the band tails, as expected [48,69]. The T -dependence of ρ in the intercalated samples is much less steep, and its values at low T are several orders of magnitude lower than that of pristine MoS 2 , consistent with a metallization induced by the electron doping.…”

“…Upon increasing electron doping, 2 H -MoS undergoes first an insulator-to-metal transition [ 46 , 47 , 48 ] and, at higher doping levels, a metal-to-superconductor transition; the superconducting phase, attained both via electrostatic carrier accumulation at the surface [ 11 , 21 , 49 , 50 ] or electrochemical ion intercalation in the bulk [ 36 , 51 , 52 ], displays a maximum transition temperature K. The highest doping levels also destabilize the 2 H -MoS crystal structure, promoting the development of charge density wave (CDW) phases [ 37 , 52 , 53 , 54 , 55 , 56 ] and/or structural transitions to other polytypes [ 53 , 54 , 55 , 57 , 58 , 59 , 60 ].…”

Coexisting superconductivity and charge-density wave in hydrogen-doped titanium diselenide via ionic liquid gating-induced protonation

“…In some cases, TMDs display a topolog-ical order, hence, once made superconducting, they may host Majorana fermions [13,14]. TMDs are also easy to handle and can be used to fabricate electronic devices [15][16][17], even printed ones [18,19]. Hence, by tailoring their physical properties, one can realize good and affordable prototypes for various quantum-technology applications, superconducting electronics, or quantum computing [20].…”

Reversible tuning of superconductivity in ion-gated niobium nitride ultrathin films by self-encapsulation with a high-$κ$ dielectric layer

“…While these additional processes can be harnessed to provide additional degrees of freedom in modulating the properties of a material, it is often desirable to ensure that the modulation occurs only in the electrostatic regime. Indeed, reversible electrostatic switching is crucial for the realization of novel device concepts, such as chiral-light emitting transistors [61], superconducting FETs [62,63], nano-constriction Josephson junctions [64,65] and metallic SC quantum interference devices [66], as well as for reliable operation of stretchable and flexible devices [67][68][69] and thermoelectric energy harvesters [70].…”