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.

The future scaling of semiconductor devices can be continued only by the development of novel nanofabrication techniques and atomically thin transistor channels. Here we demonstrate ultra-scaled MoS2 field-effect transistors (FETs) realized by a shadow evaporation method which does not require nanofabrication. The method enables large-scale fabrication of MoS2 FETs with fully gated  ∼10 nm long channels. The realized ultra-scaled MoS2 FETs exhibit very small hysteresis of current–voltage characteristics, high drain currents up to  ∼560 A m−1, very good drain current saturation for such ultra-short devices, subthreshold swing of ∼120 mV dec−1, and drain current on/off ratio of ∼106 in air ambient. The fabricated ultra-scaled MoS2 FETs are also used to realize logic gates in n-type depletion-load technology. The inverters exhibit a voltage gain of  ∼50 at a power supply voltage of only 1.5 V and are capable of in/out signal matching.

Large area molybdenum disulfide (MoS2) monolayers are typically obtained by using perylene‐3,4,9,10‐tetracarboxylic acid tetrapotassium salt (PTAS) as organic seeding promoter in chemical vapor deposition (CVD). However, the influence of the seeding promoter and the involvement of the functional groups attached to the seed molecules on the physical properties of the MoS2 monolayer are rarely taken into account. Here, it is shown that MoS2 monolayers exhibit remarkable differences in terms of the electronic polarizability by using two representative cases of seeding promoter, namely, the commercial PTAS and a home‐made perylene‐based molecule, N,N‐bis‐(5‐guanidil‐1‐pentanoic acid)‐perylene‐3,4,9,10‐tetracarboxylic acid diimide (PTARG). By thermogravimetric analysis, it is verified that the thermal degradation of the promoters occurs differently at the CVD working condition: with a single detachment of the functional groups for PTAS and with multiple thermal events for PTARG. As a consequence, the promoter‐dependent electronic polarizability, derived by free charges trapped in the monolayer, impacts on the photoluminescence emission, as well as on the electrical performances of the monolayer channel in back‐gated field‐effect transistors. These findings suggest that the modification of the electronic polarizability, by varying the molecular promoter in a pre‐growth stage, is a path to engineer the MoS2 opto‐electronic properties.

The ambipolarity of graphene is exploited to realize a new class of electronic oscillators by integrating a graphene field-effect transistor with Si CMOS logic.

Photocurrent (PC) measurements can reveal the relaxation dynamics of photoexcited hot carriers beyond the linear response of conventional transport experiments, a regime important for carrier multiplication. Here, we study the relaxation of carriers in graphene in the quantum Hall regime by accurately measuring the PC signal and modeling the data using optical Bloch equations. Our results lead to a unified understanding of the relaxation processes in graphene over different magnetic field strength regimes, which is governed by the interplay of Coulomb interactions and interactions with acoustic and optical phonons. Our data provide clear indications of a sizable carrier multiplication. Moreover, the oscillation pattern and the saturation behavior of PC are manifestations of not only the chiral transport properties of carriers in the quantum Hall regime but also the chirality change at the Dirac point, a characteristic feature of a relativistic quantum Hall effect.