Abstract
Inks based on two-dimensional (2D) materials could be used to tune the properties of printed electronics while maintaining compatibility with scalable manufacturing processes. However, a very wide range of performances have been reported in printed thin-film transistors in which the 2D channel material exhibits considerable variation in microstructure. The lack of quantitative physics-based relationships between film microstructure and transistor performance limits the codesign of exfoliation, sorting, and printing processes to inefficient empirical approaches. To rationally guide the development of 2D inks and related processing, we report a gate-dependent resistor network model that establishes distinct microstructure-performance relationships created by near-edge and intersheet resistances in printed van der Waals thin-film transistors. The model is calibrated by analyzing electrical output characteristics of model transistors consisting of overlapping 2D nanosheets with varied thicknesses that are mechanically exfoliated and transferred. Kelvin probe force microscopy analysis on the model transistors leads to the discovery that the nanosheet edges, not the intersheet resistance, limit transport due to their impact on charge carrier depletion and scattering. Our model suggests that when transport in a 2D material network is limited by the near-edge resistance, the optimum nanosheet thickness is dictated by a trade-off between charged impurity screening and gate screening, and the film mobilities are more sensitive to variations in printed nanosheet density. Removal of edge states can enable the realization of higher mobilities with thinner nanosheets due to reduced junction resistances and reduced gate screening. Our analysis of the influence of nanosheet edges on the effective film mobility not only examines the prospects of extant exfoliation methods to achieve the optimum microstructure but also provides important perspectives on processes that are essential to maximizing printed film performance.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 575-586 |
| Number of pages | 12 |
| Journal | ACS nano |
| Volume | 17 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 10 2023 |
Funding
This work was supported in part by the U.S. Department of Commerce, National Institute of Standards and Technology under financial assistance award numbers 70NANB14H012 (Z.Z.) and by the Materials Research Science and Engineering Center (MRSEC) of Northwestern University (NSF DMR-1720139) (J.-S.K., M.J.M.). It made use of the NUFAB and SPID facilities of the NUANCE Center at Northwestern University, which have received support from the Soft and Hybrid Nanotechnology Experimental (ShyNE) Resource (NSF ECCS-2025633); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. Z.Z. gratefully acknowledges support via a Hierarchical Materials Cluster Program Fellowship by the Graduate School at Northwestern University. M.J.M. gratefully acknowledges support via a 3M Fellowship as well as from the Ryan Fellowship and the Northwestern University International Institute for Nanotechnology. The authors acknowledge Sonal V. Rangnekar and Professor Mark C. Hersam for useful discussion on ink processing and printing.
Keywords
- 2D materials
- Kelvin probe force microscopy
- finite element simulation
- printed electronics
- resistor network model
- thin-film transistors
- transition metal dichalcogenides
ASJC Scopus subject areas
- General Materials Science
- General Engineering
- General Physics and Astronomy
