  Fully-depleted thick silicon Skipper-charge-coupled devices (Skipper-CCDs)
are an important technology to probe neutrino and light-dark-matter
interactions due to their sub-electron read-out noise. However, the successful
search for rare neutrino or dark-matter events requires the signal and all
backgrounds to be fully characterized. In particular, a measurement of the
electron-hole pair creation energy below 150 eV and the Fano factor are
necessary for characterizing the dark matter and neutrino signals. Moreover,
photons from background radiation may Compton scatter in the silicon bulk,
producing events that can mimic a dark matter or neutrino signal. We present a
measurement of the Compton spectrum using a Skipper-CCD and a $^{241}$Am
source. With these data, we estimate the electron-hole pair-creation energy to
be $\left(3.71 \pm 0.08\right)$ eV at 130 K in the energy range between 99.3 eV
and 150 eV. By measuring the widths of the steps at 99.3 eV and 150 eV in the
Compton spectrum, we introduce a novel technique to measure the Fano factor,
setting an upper limit of 0.31 at 90% C.L. These results prove the potential of
Skipper-CCDs to characterize the Compton spectrum and to measure precisely the
Fano factor and electron-hole pair creation energy below 150 eV.

Instrumentation and Detectors;Instrumentation and Methods for Astrophysics;High Energy Physics - Experiment