Enhanced near-Infrared Photoresponse from Nanoscale Ag-Au Alloyed Films
Posted on 2020-06-16 - 20:04
Alloying
of metals provides a vast parameter space for tuning of material,
chemical, and mechanical properties, impacting disciplines ranging
from photonics and catalysis to aerospace. From an optical point-of-view,
pure thin metal films yield enhanced light absorption due to their
cavity effects. However, an ideal metal–semiconductor photodetector
requires not only high absorption, but also long hot carrier attenuation
lengths in order to efficiently collect excited carriers. Here we
demonstrate that Ag-Au alloys provide an ideal model system for controlling
the optical and electrical responses in nanoscale thin metal films
for hot carrier photodetectors with improved performance. While pure
Ag and Au have long hot carrier attenuation lengths >20 nm, their
optical absorption is insufficient for high efficiency devices. Instead,
we find that alloying Ag and Au enhances the absorption by ∼50%
while maintaining attenuation lengths >15 nm, currently limited
by grain boundary scattering, although the electron attenuation length
of pure Au outperforms pure Ag as well as all of the alloys investigated
here. Further, our density functional theory analysis shows that the
addition of small amounts of Au to the Ag lattice significantly enhances
the hot hole generation rate. Combined, these findings suggest a route
to high efficiency hot carrier devices based on metallic alloying
with potential applications ranging from photodetectors and sensors
to improved catalytic materials.
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Krayer, Lisa J.; Palm, Kevin J.; Gong, Chen; Torres, Alberto; Villegas, Cesar E. P.; Rocha, Alexandre R.; et al. (2020). Enhanced near-Infrared Photoresponse from Nanoscale Ag-Au Alloyed Films. ACS Publications. Collection. https://doi.org/10.1021/acsphotonics.0c00140