  We demonstrate and characterize first superconducting nanowire single-photon
detectors (SNSPDs) made from atomic layer-deposited (ALD) NbN layers. To assess
the suitability of these films as a detector material, transport properties of
bare films and bridges of different dimensions and thicknesses are
investigated. Similar ratios of the measured critical current to the depairing
current are obtained for micro-bridges made from ALD and sputtered NbN films.
Furthermore, we characterized the single-photon response for 5 and 10 nm-thick
nanowire detectors. A 100 nm-wide straight nanowire with a length of 5 $\mu$m
exhibits saturated count-rate dependencies on bias current and a cut-off
wavelength in the near-infrared range. The ALD technique could open up the
possibility to fabricate NbN-based detectors on the wafer scale and to
conformally cover also non-planar surfaces for novel device concepts.
