Electronic Transport in 2D‐Based Printed FETs from a Multiscale Perspective

Abstract

As 2D materials (2DMs) gain the research limelight as a technological option for obtaining on‐demand printed low‐cost integrated circuits with reduced environmental impact, theoretical methods able to provide the necessary fabrication guidelines acquire fundamental importance. Here, a multiscale modeling technique is exploited to study electronic transport in devices consisting of a printed 2DM network of flakes. The approach implements a Monte Carlo scheme to generate the flake distribution. By means of ab initio density functional theory calculations together with non equilibrium Green's functions formalism, detailed physical insights on flake‐to‐flake transport mechanisms are provided. This later feeds a 3D drift‐diffusion and Poisson solution to compute self‐consistently transport and electrostatics in the device. The method is applied to MoS2 and graphene‐based dielectrically gated FETs, highlighting the impact of the structure density and variability on the mobility and sheet resistance. The prediction capability of the proposed approach is validated against electrical measurements of in‐house printed graphene conductive lines as a function of film thickness, demonstrating its strong potential as a guide for future experimental activity in the field.

Multiscale Simulations of 2-D Material Ink-Based Printed Network Devices

“…The current flows between source and drain metal contacts through the MoS 2 network-based channel region. The device structure is simulated using the multiscale simulation approach reported in [23], which consists of three main ingredients: 1) generation of a random distribution of flakes; 2) definition of the out-of-plane mobility; and 3) solution of transport through a drift-diffusion approximation. The first ingredient consists in generating a random distribution of flakes, with the possibility of arbitrarily setting the orientation, dimension, and overlap between flakes, using a Monte Carlo method [see Fig.…”

“…For this, we model the out-of-plane-to-in-plane conductance ratio by means of density functional theory (DFT) calculations, as presented in Figs. 2 and 3, and the Wannierization of the structure [26], which is used to perform transmission calculations within the nonequilibrium Green's function (NEGF) formalism implemented in the NanoTCAD ViDES software [23], [27]. This procedure is used to define the out-of-plane mobility, which is finally exploited, as the last ingredient, to solve the 3-D drift-diffusion equation selfconsistently with the Poisson equation to calculate the current through the device (more details on the general framework of the method used can be found in [23]).…”

“…The impact of ink properties has been considered by a synthetic factor, which we refer as the filling factor (FF) parameter, defined as the ratio of the volume occupied by the flakes to the total volume of the channel [23]. This parameter, which aims at mimicking the compactness of the network structure, depends on the ink concentration, viscosity, and the number of print passes as well as on the post-annealing process.…”

“…While in recent years, a lot of efforts have been performed in order to demonstrate the potential of this technology from an experimental point of view, a theoretical investigation of the main physical mechanisms at play in 2DM-printed devices has been so far scarcely addressed. A multiscale method has been recently presented in [23] by some of the authors in order to simulate transport in printed network based on the same type of 2-D material flakes, which has been validated against experimental results.…”

A focus review on 3D printing of wearable energy storage devices

“…The fillers used in inks can provide the desired functionalities for the end products. For energy storage devices, a variety of nanomaterials have been adopted as fillers, such as 2D nanosheets, 56 1D nanowires 57 and 0D nanoparticles 58 . For most inks used for printing energy storage devices, the concentration of the filler can play an important role in the rheology of the ink, the printed pattern structure and the functionalities of the final product.…”