Layered two-dimensional (2D) nanomaterials interact primarily via van der Waals bonding, which has created new opportunities for nanoelectronic heterostructures that are not constrained by epitaxial growth [1]. However, it is important to acknowledge that van der Waals interactions are not limited to interplanar interactions in 2D materials. In principle, any passivated, dangling bond-free surface interacts with another via non-covalent forces. Consequently, the emerging layered 2D nanomaterials can be integrated with a diverse range of other materials [2-4], including those of different dimensionality, to form van der Waals heterostructures. This talk will explore mixed dimensional combinations of 2D + n-D (n = 0, 1 and 3) materials, thus significantly expanding the van der Waals heterostructure concept. 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, and boron nitride) are isolated in solution [5-9], and then deposited into thin films with scalable additive manufacturing methods (e.g., inkjet [10], gravure [11], and screen printing [12]). By achieving high levels of nanomaterial monodispersity and printing fidelity, large-area device arrays can realize complex electronic signal conditioning such as frequency and phase shift keying [4]. Furthermore, by integrating multiple nanomaterial inks into heterostructures, unprecedented device function has been demonstrated including anti-ambipolar p-n heterojunctions [2-4] and gate-tunable memristors [13]. In addition to technological implications for nanoelectronics and optoelectronics, this work allows the exploration of several fundamental issues including band alignment, doping, trap states, and charge/energy transfer across previously unexplored mixed dimensional heterointerfaces.

[1] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, and M. C. Hersam, “Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides,” ACS Nano, 8, 1102 (2014).

[2] D. Jariwala, S. L. Howell, K.-S. Chen, J. Kang, V. K. Sangwan, S. A. Filippone, R. Turrisi, T. J. Marks, L. J. Lauhon, and M. C. Hersam, “Hybrid, gate-tunable, van der Waals p-n heterojunctions from pentacene and MoS₂,” Nano Lett., DOI: 10.1021/acs.nanolett.5b04141 (2015).

[3] D. Jariwala, V. K. Sangwan, C.-C. Wu, P. L. Prabhumirashi, M. L. Geier, T. J. Marks, L. J. Lauhon, and M. C. Hersam, “Gate-tunable carbon nanotube-MoS₂ heterojunction p-n diode,” Proc. Nat. Acad. Sci. USA, 110, 18076 (2013).

[4] D. Jariwala, V. K. Sangwan, J.-W. T. Seo, W. Xu, J. Smith, C. H. Kim, L. J. Lauhon, T. J. Marks, and M. C. Hersam, “Large-area, low-voltage, antiambipolar heterojunctions from solution-processed semiconductors,” Nano Lett., 15, 416 (2015).

[5] N. D. Mansukhani, L. M. Guiney, P. J. Kim, Y. Zhao, D. Alducin, A. Ponce, E. Larios, M. J. Yacaman, and M. C. Hersam, “High-concentration aqueous dispersions of nanoscale two-dimensional materials using nonionic, biocompatible block copolymers,” Small, DOI: 10.1002/smll.201503082 (2015).

[6] J. Zhu, X. Liu, M. L. Geier, J. J. McMorrow, D. Jariwala, M. E. Beck, W. Huang, T. J. Marks, and M. C. Hersam, “Layer-by-layer assembled two-dimensional montmorillonite dielectrics for solution-processed electronics,” Adv. Mater., DOI: 10.1002/adma.201504501 (2015).

[7] J. Zhu, J. Kang, J. Kang, D. Jariwala, J. D. Wood, J.-W. T. Seo, K.-S. Chen, T. J. Marks, and M. C. Hersam, “Solution-processed dielectrics based on thickness-sorted two-dimensional hexagonal boron nitride nanosheets,” Nano Lett., 15, 7029 (2015).

[8] J. Kang, J. D. Wood, S. A. Wells, J.-H. Lee, X. Liu, K.-S. Chen, and M. C. Hersam, “Solvent exfoliation of electronic-grade, two-dimensional black phosphorus,” ACS Nano, 9, 3596 (2015).

[9] J. Kang, J.-W. T. Seo, D. Alducin, A. Ponce, M. J. Yacaman, and M. C. Hersam, “Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation,” Nature Communications, 5, 5478 (2014).

[10] E. B. Secor, P. L. Prabhumirashi, K. Puntambekar, M. L. Geier, and M. C. Hersam, “Inkjet printing of high conductivity, flexible graphene patterns,” J. Phys. Chem. Lett., 4, 1347 (2013).

[11] E. B. Secor, S. Lim, H. Zhang, C. D. Frisbie, L. F. Francis, and M. C. Hersam, “Gravure printing of graphene for large-area flexible electronics,” Adv. Mater., 26, 4533 (2014).

[12] W. J. Hyun, E. B. Secor, M. C. Hersam, C. D. Frisbie, and L. F. Francis, “High-resolution patterning of graphene by screen printing with a silicon stencil for highly flexible printed electronics,” Adv. Mater., 27, 109 (2015).

[13] V. K. Sangwan, D. Jariwala, I. S. Kim, K.-S. Chen, T. J. Marks, L. J. Lauhon, and M. C. Hersam, “Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS₂,” Nature Nanotechnology, 10, 403 (2015).