Transparent metal oxides have unmatched properties for driving future thin film electronics, displaying high transparency, high electron mobility, and the ability to achieve efficient transport in both their amorphous and nanocrystalline state. The ability to solution-process and print metal oxide semiconductors has the potential to deliver new large area applications in optoelectronic devices for energy, display, and sensing applications. However, these new applications demand precise control of conducting oxides’ optoelectronic properties at the nanoscale, particularly in ultrathin oxide semiconductors (< 20 nm) highly sensitive to interfacial effects.
Here, we present a review of the state of the art of ultrathin transparent conducting oxides (TCOs), towards an understanding of the material origins of their closely coupled and unique optical, mechanical, and electrical properties. We will discuss the engineering of this class of materials as degenerate TCOs for energy devices and as semiconducting channel materials for transparent switching devices. We will also discuss our recent work in developing synthetic strategies for 2-dimensional TCOs formed from the Cabrera-Mott surface oxides on liquid metals and we will consider the impact of quantum confinement on TCOs’ optoelectronic properties. Finally, we will consider how band engineering and modulation doping could provide new opportunities for high-frequency electronics and tunable optics.

William Scheideler graduated summa cum laude from Duke University in 2013 with a B.S. in Electrical Engineering and a B.S. in Biomedical Engineering. He completed his Ph.D. as an NSF Graduate Research Fellow in Electrical Engineering at the University of California, Berkeley. His doctoral thesis explored scalable nanomanufacturing of transparent metal oxide electronics. He then completed his postdoctoral studies in the Department of Materials Science and Engineering at Stanford University, where he studied scalable fabrication and thermomechanical reliability of perovskite solar cells. Will joined the faculty of Dartmouth College’s Thayer School of Engineering in 2019 as an Assistant Professor. His current research interests include 2D materials, 3D electronics integration, and advanced devices for sensing and energy harvesting.