  Accessing unexplored conditions in crystal growth often reveals remarkable
surprises and new regimes of physical behavior. In this work, performing
molecular beam epitaxy of the technologically important superconductor NbN at
temperatures greater than 1000$^\circ$C, higher than in the past, is found to
reveal persistent RHEED oscillations throughout the growth, atomically smooth
surfaces, normal metal resistivities as low as 37$\mu\Omega$-cm and
superconducting critical temperatures in excess of 15 K. Most remarkably, a
reversal of the sign of the Hall coefficient is observed as the NbN films are
cooled, and the high material quality allows the first imaging of Abrikosov
vortex lattices in this superconductor.
