ZnO/CuCrO2 Core–Shell Nanowire Heterostructures for Self-Powered UV Photodetectors with Fast Response

An original self-powered UV photodetector integrating ZnO/CuCrO2
core–shell nanowire heterostructures is fabricated using low-cost and scalable
chemical deposition techniques operating at moderate temperatures. A
35 nm thick delafossite phase CuCrO2 shell is formed with high uniformity by
aerosol-assisted chemical vapor deposition over an array of vertically aligned
ZnO nanowires grown by chemical bath deposition. The CuCrO2 shell consists
of columnar grains at the top of ZnO nanowires as well as nanograins with
some preferential orientations on their vertical sidewalls. The ZnO/CuCrO2
core–shell nanowire heterostructures exhibit significant diode behavior, with
a rectification ratio approaching 1.2 × 104 at ±1 V, as well as a high optical
absorptance above 85% in the UV part of the electromagnetic spectrum.
A high UV responsivity at zero bias under low-power illumination of up to
3.43 mA W−1 under a 365 nm UV lamp, and up to 5.87 mA W−1 at 395 nm
from spectrally resolved measurements, alongside a high selectivity with a
UV-to-visible (395–550 nm) rejection ratio of 106 is measured. The short rise
and decay times of 32 and 35 μs, respectively, both measured at zero bias,
further establish these devices as promising candidates for cost-efficient,
all-oxide self-powered UV photodetectors.