Materials Science Research Lecture

Two-dimensional (2D) materials have emerged as promising candidates for next-generation electronic and optoelectronic applications. Much of the early work in this field has focused on measuring and optimizing intrinsic properties on small samples under idealized conditions. However, real-world applications inevitably require large-area samples that are integrated with dielectrics, contacts, and other semiconductors in ambient conditions. This talk will thus explore methods for improving the uniformity of solution-processed 2D materials with an eye toward realizing scalable processing of large-area thin-films. For example, density gradient ultracentrifugation allows the solution-based isolation of 2D transition metal dichalcogenides and boron nitride with homogeneous thickness down to the single-layer limit. Similarly, 2D black phosphorus is isolated in solution with the resulting flakes showing transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes. In addition to solution processing, this talk will also report on the integration of 2D materials with dielectrics and other semiconductors. In particular, atomic layer deposition of dielectrics and covalent organic adlayers on 2D black phosphorus suppress ambient degradation while preserving or enhancing electronic properties. Finally, gate-tunable p-n heterojunction diodes with Type I and Type II band alignments are demonstrated by integrating n-type single-layer MoS2 with p-type semiconducting single-walled carbon nanotubes and pentacene, respectively.