Ongoing and Future research activities in the rapidly developing field of molecular beam epitaxy at PDI

 

Molecular beam epitaxy as thin film growth technique allows for unparalleled control, precision, and cleanliness of materials. It has driven in parts the first quantum revolution by providing a prerequisite to realize light emitters, lasers, high speed electronic switches, electric field tunable plasmonic structures and other technological advances benefitting our society: the ability to engineer electronically and optically active materials with dramatically reduced defect concentration so that the intrinsic physics at reduced dimensions could be harnessed. While this has been done with remarkable success in various traditional semiconductor materials using molecular beam epitaxy, ranging from mono-elemental Group IV, to Group III-V all the way to Group II-VI compound semiconductors, it has been found challenging to expand this synthesis concept to other material classes. 

Currently we are witnessing the technological realization of the second quantum revolution, where not only the transition probability into other quantum states or the square modulus of the electron wave function is the targeted functionality. Rather, we want to push beyond that aiming to utilize quantum mechanical properties, such as the phase or entanglement of quantum states, to unleash the full potential quantum mechanics is offering. In this regard the synthesis of new functional materials, such as layered chalcogenides, Heusler alloys, twisted graphene, functional complex oxides exhibiting strong electron correlation, large spin-orbit coupling, non-trivial topologies, are coming into focus. In these emerging materials a minimal intrinsic and extrinsic defect concentration is demanded as well, where now additional phenomena, such as decoherence of quantum states, have to be taken into consideration. For complex oxides materials containing two or more cations this have been proved inherently difficult, provoking the question: 

 

Can we even achieve semiconductor-grade quality complex oxide thin films?

 

In this talk I will introduce the fundamental challenges utilizing conventional molecular beam epitaxy for the growth of complex oxides. I will then present an alternative – a hybrid MBE synthesis approach – as a potential way out to overcome these challenges. Promising results obtained by hybrid oxide MBE will be discussed along with the most recent advances in materials quality achieved in complex oxides thin films with perovskite structure. An outlook will be given about the possibility to scale up this growth approach to larger substrates and higher growth rates, rendering its potential relevance in an industrial setting.