Tunable localized surface plasmon resonance of subwavelength Cu/SiO2/Al plasmonic antenna

摘要

The ability to alter the response of an optical antenna is highly desirable, since it allows for a much greater flexibility in the design and operation of optical circuits. A very recent approach has leveraged on the resistance switchability and the rich plasmonic properties of the metal/insulator/metal system to achieve programmable plasmonic antennas, whereby the spectral response is modified electrically through controlling the formation/dissolution of a metal filament in the insulator layer. However, studies reported up-to-date on tunable plasmonic antennas are based mostly on either Au or Ag. Additionally, most of them are operating in the infrared range. Here, we elucidate numerically, using finite-difference time-domain method, the potential of a CMOS compatible Cu/SiO₂/Al tunable plasmonic antenna operating in the visible range. Our choice of this material system is motivated by its excellent resistance switching properties, which are being exploited for resistive random access memory applications via back-end interconnect integration. Simulation results show that tuning of the localized surface plasmon resonance (LSPR) wavelength can be achieved with a nanoscale Cu filament embedded in the SiO₂ layer, with the tuning bandwidth being dependent on several factors like size and position of the Cu filament, as well as the number of such filaments. The blue-shifted LSPR response may be ascribed to a change in the SiO₂ permittivity due to the presence of the Cu filament in the former, under the framework of the effective medium theory. In conjunction with the demonstrated ability to electrically control the formation/dissolution of a Cu filament through anodic oxidation of the Cu electrode, this work suggests the possibility of a dynamically reconfigurable Cu plasmonic antenna with an immediate full compatibility with the mainstream integrated circuit technology for on-chip tunable photodetection applications.