Scanning Probe Microscopy development and applications for time resolved structure-function studies

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Atomic force microscopy (AFM) is an ideal experimental platform for nanoscience and nanotechnology. It allows the imaging, manipulation and characterization of individual nanometer sized objects. In the past five years the focus of my research was on developing methods to measure the electronic properties of nanoscale systems. A particular aim was to develop time resolved measurement capabilities. We have succeeded in advancing AFM techniques to allow the determination of properties via spatially and time resolved AFM spectroscopy methods using electrostatic tip-sample interactions. We achieved the fastest ever reported time resolution by resolving a 100fs non-linear optical signal by AFM. A further major achievement was the measurement of the electron transfer process on a single molecule by AFM, allowing us to determine electron-phonon coupling, molecular vibration and reorganization energies. In the next 5 years the goal of my research program is to build on some of the recently achieved experimental breakthroughs and gain a fundamental understanding of the structure-function relation of nanoscale systems. Materials to be investigated have a long term potential for renewable energy generation, information storage or quantum information processing. A particular focus will be to investigate the role of defects and disorder on the dynamics of the process of interest. This research program provides a rich, interdisciplinary and world-class environment for the training of highly qualified personnel, develops new instrumentation and methods, addresses fundamental questions and has major application potential. Specifically, we plan to use our cryogenic AFM to characterize the charging and coupling energies of individual dopant atoms in silicon, relevant in quantum information. These efforts will be in collaboration with Prof. N. Curson at University College London. Similarly, we will investigate electron transfer in proteins to understand the detailed structure-function relation in biological charge funnel systems to elucidate general principles as input to biomimetic efforts to engineer efficient hydrogen and electricity generating materials. For this, we will collaborate with world-class theorists Profs. H. Guo and K. Bevan. We will develop spatially resolved non-linear optical measurements using AFM as a detector to investigate light-matter interactions, specifically in organic and 2 dimensional systems. We want to understand how size, order and defects in these systems determines conductivity and opto-electronic properties. By pumping the sample with 100 fs optical pulses we will generate excitons and ultimately free charges. The properties of these will be characterized by AFM with nanometer spatial and ultrafast time resolution using pump-probe and non-linear optics methods. Achieving this will open a wide new field of inquiry: studying the properties of individual structures in contrast to ensemble averaging.