Layered two-dimensional (2D) materials interact primarily via van der Waals bonding, which has created new opportunities for heterostructures that are not constrained by epitaxial growth [1]. Since any passivated, dangling bond-free surface interacts with another via non-covalent forces, layered 2D materials can also be integrated with a diverse range of other materials, including those of different dimensionality, to form mixed-dimensional van der Waals heterostructures [2]. Furthermore, chemical functionalization provides additional opportunities for tailoring the properties of 2D materials [3] and the degree of coupling across heterointerfaces [4]. In order to efficiently explore the vast phase space for mixed-dimensional heterostructures, our laboratory employs solution-based additive assembly. In particular, constituent nanomaterials (e.g., carbon nanotubes, graphene, transition metal dichalcogenides, black phosphorus, hexagonal boron nitride, indium selenide, and transition metal halides) are isolated in solution, and then deposited into thin films with scalable additive manufacturing methods [5,6]. By achieving high levels of nanomaterial monodispersity and printing fidelity, a variety of electronic and energy applications can be enhanced including photodetectors, optical emitters, supercapacitors, and batteries [7-10]. Furthermore, by integrating multiple nanomaterials into heterostructures, unprecedented device function can be realized including anti-ambipolar transistors, gate-tunable Gaussian heterojunction transistors, and neuromorphic memtransistors [11-14].

[1] D. Lam, et al., ACS Nano, 16, 7144 (2022).
[2] D. Jariwala, et al., Nature Materials, 16, 170 (2017).
[3] S. H. Amsterdam, et al., Journal of Physical Chemistry Letters, 12, 4543 (2021).
[4] S. Padgaonkar, et al., Accounts of Chemical Research, 53, 763 (2020).
[5] C. M. Thomas, et al., ACS Energy Letters, 7, 1558 (2022).
[6] D. Lam, et al., ACS Nano, 16, 11315 (2022).
[7] M. E. Beck and M. C. Hersam, ACS Nano, 14, 6498 (2020).
[8] K.-Y. Park, et al., Advanced Energy Materials, 10, 2001216 (2020).
[9] W. J. Hyun, et al., Advanced Materials, 33, 2007864 (2021).
[10] K.-Y. Park, et al., Advanced Materials, 34, 2106402 (2022).
[11] M. E. Beck, et al., Nature Communications, 11, 1565 (2020).
[12] V. K. Sangwan and M. C. Hersam, Nature Nanotechnology, 15, 517 (2020).
[13] J. Yuan, et al., Nano Letters, 21, 6432 (2021).
[14] X. Yan, et al., Advanced Materials, 34, 2108025 (2022).

Mark Hersam

Northwestern University

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