In-situ TEM holder for ultrafast, multimodal imaging

Many energy conversion and transfer processes critically depend on the material nanostructure details and its response to external excitation fields. Surface and volume defect formation and migration in conjunc- tion with carrier transport processes have a profound impact on the opto-electro-thermo-mechanical prop- erties of materials. Understanding these phenomena requires a unique combination of advanced atomic- scale imaging with controlled nanoscale excitation and quantitative probing of fundamental processes. The proposed innovation is focused on a method for simultaneous nanoscale multimodal imaging of en- ergy conversion/transfer processes by integrating tip-based pulsed laser radiation sources within a trans- mission electron microscope (TEM). Nanoscale confinement of radiation fields of enhanced intensity un- derneath a tip-based probe enables unambiguous and direct in-situ interrogation of the nanostructural ef- fects on the material properties. In this project, an apparatus combining nanoscale laser excitation and optical signal collection of photoluminescence (PL), time-resolved photoluminescence (TRPL), ultrafast optical probing and Raman spectra will be designed, tested and integrated into a TEM holder. In Phase I, tapered fiber and near field probe tips have been employed for excitation of the optical response of the specimen with nanoscale spatial resolution. Custom miniature optics for efficient signal collection and a benchtop prototype apparatus has been designed and constructed, which enabled far-field and near-field PL spectroscopy while meeting the requirements for implementation into the TEM instrumentation.Based on this work, Phase II project is proposed to construct and test an integrated TEM holder for in-situ multimodal optical spectroscopy and validate its performance via detailed ex-situ TEM experiments and analytical diagnostics. Furthermore, the prototype will be tested in the real scientific studies, for example, in-situ characterization of defects in the synthesis of nanostructures. The outcome of this project will enable a widespread adoption of unique facility for the in situ direct cor- relation of optical spectroscopy with atomic level imaging. This entirely new capability will undoubtedly have a profound impact to the fields of Materials Science and Manufacturing. The users of the proposed approach can embark on a host of fundamental studies on the true nanoscale interaction of photons with materials that are impossible to conduct by the presently available instrumentation. For instance, the in- situ laser probe will give a user a front row seat to examining fundamental features of energy conversion and transfer processes