Hot Carrier Generation in Metallic Nanostructures: Mechanisms and Novel Devices
Halas, Naomi J
Doctor of Philosophy
Hot carrier generation in metallic nanostructures offers a potential route to circumventing thermodynamic efficiencies of traditional light-harvesting devices and structures. However, previous experimental realizations of hot electron devices have shown low photo-conversion efficiencies. Several theoretical works have sought to understand the fundamental processes behind hot carrier generation and explore routes toward increasing the carrier generation efficiency. In this thesis, we discriminate between hot carrier generation from interband transitions and surface plasmons by comparing photocurrent generation in Schottky and ohmic devices. By comparing the functional form of the two types of photocurrent generation, we show that hot carrier generation in metallic nanostructures obeys the field intensity inside the metallic nanostructure, paving the way towards more efficient plasmon-induced hot carrier devices. Next, I focus on plasmonic photodetectors for the mid-IR spectral region, a technologically and scientifically important spectral region where molecular vibrational resonances exist. Despite the significance of the mid-IR, the low energy of mid-IR photons poses significant challenges for efficient photodetection and light emission. We circumvent the limitations of traditional mid-IR photodetectors by exploiting hot carrier generation in metals and demonstrate a novel uncooled CMOS-compatible photodetector for the middle wave infrared (mid-IR) spectral region.
Plasmonics; nanophotonics; device physics; hot carrier physics