  The rare-earth nickelates possess a diverse set of collective phenomena
including metal-to-insulator transitions, magnetic phase transitions, and, upon
chemical reduction, superconductivity. Here, we demonstrate epitaxial
stabilization of layered nickelates in the Ruddlesden-Popper form,
Nd$_{n+1}$Ni$_n$O$_{3n+1}$, using molecular beam epitaxy. By optimizing the
stoichiometry of the parent perovskite NdNiO$_3$, we can reproducibly
synthesize the $n = 1 - 5$ member compounds. X-ray absorption spectroscopy at
the O $K$ and Ni $L$ edges indicate systematic changes in both the
nickel-oxygen hybridization level and nominal nickel filling from 3$d^8$ to
3$d^7$ as we move across the series from $n = 1$ to $n = \infty$. The $n = 3 -
5$ compounds exhibit weakly hysteretic metal-to-insulator transitions with
transition temperatures that depress with increasing order toward NdNiO$_3$ ($n
= \infty)$.
