  Multifunctional thin films in energy-related devices often must be
electrically insulating where a single nanoscale defect can result in complete
device-scale failure. Locating and characterizing such defects presents a
fundamental problem where high-resolution imaging methods are needed to find
defects, but imaging with high spatial resolution limits the field of view and
thus the measurement throughput. Here, we present a novel high-throughput
method for detecting sub-micron defects in insulating thin films by leveraging
the electrochemiluminescence (ECL) of luminol. Through a systematic study of
reagent concentrations, buffers, voltage, and excitation time, we identify
optimized conditions at which it is possible to detect features with areas ~500
times smaller than the area interrogated by a single pixel of the camera,
showing high-throughput detection of sub-micron defects. In particular, we
estimate the minimum detectable features to be lines as narrow as 2.5 nm in
width and pinholes as small as 35 nm in radius. We further explore this method
by using it to characterize a nominally insulating phenol film and find
conductive defects that are cross-correlated with high-resolution atomic force
microscopy to provide feedback to synthesis. Given the inherent
parallelizability and scalability of this assay, it is expected to have a major
impact on the automated discovery of multifunctional films.
