Nano Seminar: “Conductive Nitrides for Plasmonics in the Visible Region: Properties and Applications”

Plasmonic nanostructure based on silver and gold that produces LSPR to withstand ultrahigh temperatures without damage remains a great challenge for future ultra-compact integrated circuits, and high-power enabled photonic devices. In principle, the shapes of plasmonic nanostructures containing noble metals would change after the heat treatment that altered the plasmonic resonance. Thus, discovering refractory plasmonic materials that can exhibit plasmonic resonance in the visible range is essential. A challenge in refractory plasmonic materials is the bulk plasmon frequency is usually in the near-infrared range, making it difficult to generate plasmonic colors in the visible. We first reported a new refractory plasmonic material HfN, one of the conductive nitrides, that has a relatively high bulk plasmon frequency (λ = 400 nm) with a high melting point (T ∼ 3583 K) and a relatively large magnitude of the real part of the permittivity, which enables intense local electromagnetic field confinement to form LSPR in the visible region. We use this unique property to develop full-color plasmonic pixels with sub-diffraction resolution through tailoring HfN plasmonic crystals and demonstrate that HfN refractory plasmonic crystals can withstand high-temperature annealing (900 °C) without damage. The novel HfN refractory plasmonic materials unlock new opportunities for ultra-compact integrated functional plasmonic devices. Especially the unique property of HfN, implying a bright future for emerging plasmonic materials at visible wavelengths [1]. In addition, I will present an overview of my research works over the past five years on the plasmon-enhanced light-matter interactions in the visible regions and their applications [1-6], including the plasmonic nanolasers [2-3], tunable plasmonic modulators [4], plasmonic phototransistors [5], plasmon-enhanced solar energy harvesting [6], and the refractory plasmonic colors for back-light free displays [1]. My group discovered several unique working mechanisms that utilize plasmonic nanocavities to improve optoelectronic device performance. More recently, we demonstrated the scalable 2D FET device fabrication and characterization [7].  By engineering the local electromagnetic field confinement, the light-matter interaction strength can be enhanced, which results in efficient energy conversion in the designed nanosystem. Lastly, I will discuss detailed mechanisms and possible applications. These results have broad implications for the use of alternative plasmonic nanocavities in high-performance optoelectronic devices.