Charge transfer exciton dynamics at diamond-hBN interface

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Nontechnical description Interfaces between dissimilar materials such as diamond and boron nitride offer exciting possibilities for realizing exceptional electronic, optical, magnetic, and chemical properties. In this project, the research team explores these possibilities by studying the interaction of charges at the interface between diamond and hexagonal boron nitride. This boundary can be finely tuned by altering the chemical composition at the surface of the diamond, the number of boron nitride layers, and the angle at which these materials meet, providing broad design flexibility. The team uses this tunability to investigate how bound pairs of excited electrons and their corresponding positively charged empty states, which are known as excitons, form, relax, and move across the interface. The researchers employ advanced optical techniques and theoretical calculations to understand the unknown behavior of these excitons, focusing on how their dynamics change with temperature and modifications to the structure. This research could pave the way for new applications in energy conversion, optoelectronics, and microelectronics. Additionally, the project provides valuable training for graduate and undergraduate students in cutting-edge experimental and computational methods. To address education at the grassroot level, the team in collaboration with Museum of Natural History at University of Michigan will engage middle school students in scientific research via curriculum development and summer programs. Technical description Van der Waals semiconductor heterointerfaces present an opportunity to develop new classes of material systems with superior electronic, optical, magnetic and chemical properties. In this project, the research team theoretically and experimentally investigates the charge transfer excitons at the diamond-hexagonal boron nitride heterointerface. This interface provides immense design flexibility of the heterointerface due to the band alignment tunability via surface passivation of diamond, number of boron nitride layers, and orientation twist angle between the two materials. The research team utilizes this tunability to explore the formation/relaxation dynamics and transport properties of charge transfer excitons. They employ advanced optical spectroscopy, along with guidance from first-principles calculations, to unravel the unknown physics associated with charge-transfer excitons, and specifically their thermalization dynamics and transport dynamics as a function of temperature to reveal the potential pathways to control it. The tightly weaved experiment-theory effort is imperative for the development of a potential excitonic material system to serve applications in energy conversion, optoelectronic, and micro-electronics. The energy transfer and transport associated with charge-transfer excitons combining diamond and boron nitride remains an unexplored territory of research and thus, presents a unique opportunity to develop a new class of material systems for opto-excitonics. By combining two quantum ready scalable systems, the research team aims to establish diamond/boron nitride interfaces as a platform for room temperature excitonic devices. The project also provides training for graduate and undergraduate students in state-of-the-art experimental and computational techniques. The topic of two-dimensional semiconductors is particularly well suited to introduce a wide range of nanotechnology-related themes. Thus, the research-team will engage in curriculum development and summer programs for middle school students in collaboration with the Museum of Natural History at University of Michigan. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.