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Plasmonic nanostructures with electrical connections have potential applications as new electro-optic devices due to their strong light–matter interactions. Plasmonic dimers with nanogaps between adjacent nanostructures are especially good at enhancing local electromagnetic (EM) fields at resonance for improved performance. In this study, we use optical extinction measurements and high-resolution electron microscopy imaging to investigate the thermal stability of electrically interconnected plasmonic dimers and their optical and morphological properties. Experimental measurements and finite difference time domain (FDTD) simulations are combined to characterize temperature effects on the plasmonic properties of large arrays of Au nanostructures on glass substrates. Experiments show continuous blue shifts of extinction peaks for heating up to 210°C. Microscopy measurements reveal these peak shifts are due to morphological changes that shrink nanorods and increase nanogap distances. Simulations of the nanostructures before and after heating find good agreement with experiments. Results show that plasmonic properties are maintained after thermal processing, but peak shifts need to be considered for device design.
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Interconnected Plasmonic Nanogap Antennas for Sub-Bandgap Photodetection via Hot Carrier Injection
Modern integrated circuits have active components on the order of nanometers. However, optical devices are often limited by diffraction effects with dimensions measured in wavelengths. Nanoscale photodetectors capable of converting light into electrical signals are necessary for the miniaturization of optoelectronic applications. Strong coupling of light and free electrons in plasmonic nanostructures overcomes these limitations by confining light into sub-wavelength volumes with intense local electric fields. Localized electric fields are intensified at nanorod ends and in nanogap regions between nanostructures. Hot carriers generated within these high-field regions from nonradiative decay of surface plasmons can be injected into the conduction band of adjacent semiconductors, enabling sub-bandgap photodetection. The optical properties of these plasmonic photodetectors can be tuned by modifying antenna materials and geometric parameters like size, thickness, and shape. Electrical interconnects provide connectivity to convert light into electrical signals. In this work, interconnected nanogap antennas fabricated with 35 nm gaps are encapsulated with ALD-deposited [Formula: see text], enabling photodetection via Schottky barrier junctions. Photodetectors with high responsivity (12[Formula: see text][Formula: see text]A/mW) are presented for wavelengths below the bandgap of [Formula: see text] (3.2[Formula: see text]eV). These plasmonic nanogap antennas are sub-wavelength, tunable photodetectors with sub-bandgap responsivity for a broad spectral range.
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- PAR ID:
- 10608905
- Publisher / Repository:
- World Scientific Publishing Company
- Date Published:
- Journal Name:
- International Journal of High Speed Electronics and Systems
- Volume:
- 33
- Issue:
- 02n03
- ISSN:
- 0129-1564
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1142/S0129156424400524
