Metal Oxide Heterointerfaces in Hybrid Electronic Platforms.

Abstract

This special issue is dedicated to the characterization of metal oxide interfaces and surfaces in electronic platforms. The theme emerged following a new Materials Research Society (MRS) Symposium presented first at the Fall 2014 Boston meeting and updated at the Spring 2016 Phoenix meeting. Both symposia attracted researchers from across the materials science & engineering, chemistry, physics, and electronics communities and highlighted the importance of the theme in these diverse fields. This special issue serves to highlight some of the applications of metal oxide surfaces and interfaces, and also showcases the importance of an holistic and multidisciplinary characterization approaches to elucidate functionality. Metal oxides are attractive materials for many energy-conversion technologies, in that the energetic position and distributions of the bulk transport bands are readily defined and easily manipulated through synthesis. However, at the surface, the frontier molecular orbitals can participate in interfacial reaction phenomena, resulting in changes to: i) surface conductivity and carrier density; ii) near-surface chemical composition and electronic gaps; iii) surface reaction chemistries with subsequent layers; and/or iv) free-carrier dynamic behavior across the interface. Irrespective of the specific application or research topic, a detailed understanding of interfaces is critical, both from a basic science perspective and for the continued development of the many technologies described herein. During the preparation of this special issue, it became apparent that the very concept of an interface has different meanings for those in different scientific communities. The most striking observation is the huge variation in the length scale that is considered to be interfacial. For some, the precise atomic or molecular nature of species at the boundary between two materials is critical. For others, the nature of the near-surface species and the change when the bulk is approached is significant. As a consequence there is a diverse range of analytical techniques utilized to better understand the chemical, optical, and electrical properties of such interfaces. Controlling and modifying the nature of “as prepared” surfaces continues to be a hot topic. Likewise, many are now considering interfacial phenomena that arise during the operation of devices and how such surfaces may evolve during the lifetime of an interface. The desire to probe both accessible and buried interfaces has emerged as a resonating theme in this special issue. In operando characterization is a topic that we believe will garner increased interest and focus across a wide range of materials systems and technology platforms. Here, we bring together 11 manuscripts from internationally leading researchers. The articles cover applications ranging from current to next-generation photovoltaics, thin-film transistors, and transparent conducting electrodes, and provide detailed descriptions of materials synthesis, and materials processing, as well as static and in operando characterization. Common to all articles is the description of metal oxides interfaced with organic species, metals, and electrolytes, as well as fundamental properties of oxide materials that are highly promising due to their superior performance and earth abundance. Martyn A. McLachlan obtained his B.Sc. (Hons) in chemistry from the University of Paisley (2001) and subsequently his Ph.D. from the University of Glasgow (2005); he then joined the Department of Materials, Imperial College London, as a postdoctoral researcher. He was awarded a Royal Academy of Engineering Research Fellowship (2007–2012) followed by his appointment as Lecturer and more recently (2015) as Senior Lecturer. His current research interests are focused on the growth of metal oxide thin films and their integration into optoelectronic device platforms, with particular emphasis on structural and interfacial characterization. Erin L. Ratcliff received her Ph.D. in Physical Chemistry from Iowa State University in 2007. After post-doctoral research and serving as a research scientist and research professor in the Chemistry Department at the University of Arizona, she joined the faculty in the Department of Materials Science and Engineering in 2014. Her current research interests include: spectroscopic and electrochemical characterization of metal oxide interfaces for photoelectrochemical cells, organic electronics, and bioelectronic materials and devices.