We have performed photoemission (PE) spectroscopy of $\beta \text{−}\mathrm{ZrNCl}$ and ${\mathrm{Na}}_x\mathrm{ZrNCl}$ to study intercalation-induced change in the electronic structure. The valence band PE spectrum of $\beta \text{−}\mathrm{ZrNCl}$ shows a small intensity region within $\sim 2.5\mathrm{eV}$ of $E_F$ with a very small hump at $E_F$ that can be ascribed to hydrogen impurity states. These provide spectroscopic evidence that $\beta \text{−}\mathrm{ZrNCl}$ is an $n$-type semiconductor. Upon Na intercalation, new states possibly involving hybridized $\mathrm{Zr}4d$ and $\mathrm{N}2p$ systematically evolve at $E_F$, with a negligible shift in the valence band structures. Similar results in $\beta \text{−}\mathrm{HfNCl}$ and ${\mathrm{Na}}_x\mathrm{HfNCl}$ indicate that these results represent common electronic features of the layered nitride chloride superconductors.

• Received 15 June 2004

DOI:https://doi.org/10.1103/PhysRevB.70.193103