CAREER: Optical Super-Resolution Nanothermometry via Stimulated Emission Depletion Imaging

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We live in an era of nanotechnology, where omnipresent devices like the laptops and smart phones that power our communications, the hard drives that store our data, and the light-emitting diodes that illuminate our buildings contain a multitude of nanoscale components. Increasingly, these electronic, data storage, and energy conversion devices must also operate under challenging conditions, including extreme temperatures, high pressures, large electromagnetic fields, and harsh chemical environments. Simultaneously, thermal properties play an outsize role in determining the overall performance of these technologies. For example, poor heat dissipation can limit the reliability of electronics and hard drives, while high-performance thermal insulation materials instead must greatly reduce heat transfer. Non-invasive temperature mapping with nanoscale spatial resolution is thus critical for optimizing the performance and reliability of a wide array of modern technologies. However, most existing thermometry techniques either require physically contacting samples with a temperature probe, which can perturb the sample and preclude measurements in challenging environments, or else lack the spatial resolution needed to resolve nanoscale temperature heterogeneities. The central goal of this proposal is to address these challenges by developing a novel super-resolution nanothermometry technique, enabling far-field optical temperature mapping with sub-diffraction limited spatial resolution. The proposed technique relies on luminescent nanomaterials called upconverting nanoparticles that can operate under wide-ranging conditions and independent of sample form factor or material type. Using a custom-built imaging and spectroscopy system, the principal investigator and her research team will adapt a Nobel Prize-winning super-resolution imaging technique called stimulated emission depletion for thermometry. The team will demonstrate temperature-dependent stimulated emission depletion spectroscopy, use spatially resolved stimulated emission depletion measurements to map surface temperature profiles of microfabricated heater structures with spatial resolution down to ~60 nm, and apply stimulated emission depletion nanothermometry to uncover failure mechanisms in operating optoelectronic devices, a major challenge that cannot be fully addressed by existing techniques. In concert, the integrated education plan will democratize thermal microscopy via the creation of an open source hardware repository and help ensure full participation of the next generation of underrepresented groups in science and engineering fields through an elementary school outreach partnership.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.