M.C. Hersam
Northwestern University,
United States
Keywords: graphene, 2D materials
Summary:
Two-dimensional nanomaterials have emerged as promising candidates for next-generation electronics and optoelectronics [1], but advances in scalable nanomanufacturing are required to exploit this potential in real-world technology. This talk will explore methods for improving the uniformity of solution-processed two-dimensional nanomaterials with an eye toward realizing dispersions and inks that can be deposited into large-area thin-films [2]. In particular, density gradient ultracentrifugation allows the solution-based isolation of boron nitride [3], montmorillonite [4], and transition metal dichalcogenides (e.g., MoS2, WS2, ReS2, MoSe2, WSe2) [5,6] with homogeneous thickness down to the atomically thin limit. Similarly, two-dimensional black phosphorus is isolated in organic solvents [7] or deoxygenated aqueous surfactant solutions [8] with the resulting phosphorene nanosheets showing field-effect transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes. By adding cellulosic polymer stabilizers to these dispersions, the rheological properties can be tuned by orders of magnitude, thereby enabling two-dimensional nanomaterial inks that are compatible with a range of additive manufacturing methods including inkjet [9], gravure [10], screen [11], and 3D printing [12]. The resulting printed two-dimensional nanomaterial structures show promise in several applications including photodiodes [13], anti-ambipolar transistors [14], gate-tunable memristors [15], and heterojunction photovoltaics [16]. References: [1] D. Jariwala, et al., ACS Nano, 8, 1102 (2014). [2] E. B. Secor, et al., Journal of Physical Chemistry Letters, 6, 620 (2015). [3] J. Zhu, et al., Nano Letters, 15, 7029 (2015). [4] J. Zhu, et al., Advanced Materials, 28, 63 (2016). [5] J. Kang, et al., Nature Communications, 5, 5478 (2014). [6] J. Kang, et al., Nano Letters, DOI: 10.1021/acs.nanolett.6b03584 (2016). [7] J. Kang, et al., ACS Nano, 9, 3596 (2015). [8] J. Kang, et al., Proc. Nat. Acad. Sci. USA, 113, 11688 (2016). [9] E. B. Secor, et al., Journal of Physical Chemistry Letters, 4, 1347 (2013). [10] E. B. Secor, et al., Advanced Materials, 26, 4533 (2014). [11] W. J. Hyun, et al., Advanced Materials, 27, 109 (2015). [12] A. E. Jakus, et al., ACS Nano, 9, 4636 (2015). [13] D. Jariwala, et al., Proc. Nat. Acad. Sci. USA, 110, 18076 (2013). [14] D. Jariwala, et al., Nano Letters, 15, 416 (2015). [15] V. K. Sangwan, et al., Nature Nanotechnology, 10, 403 (2015). [16] D. Jariwala, et al., Nano Letters, 16, 497 (2016).