Electron-Paramagnetic-Resonance Studies on Arsenic Acceptors in Natural (2H) and Synthetic (3R) MoS2Crystals

We have observed the EPR spectra of As acceptors in both natural Mo${\mathrm{S}}_2$ crystals ($2H$ polytype) and in synthetic Mo${\mathrm{S}}_2$ crystals ($3R$ polytype). The $g$ values of the resonance signals show that the As acceptors are associated with a band that has $d_{z^2}$ orbital character. Energy considerations indicate that the As acceptors are most likely substitutional on sulfur sites. The observation of $d_{z^2}$ orbital character for the As acceptors on sulfur sites is only consistent with a Mo${\mathrm{S}}_2$ band structures that has the $d_{z^2}$ band as the highest filled band. In one of our samples the concentration of As acceptors was low enough so that some of the holes introduced by the As acceptors were localized at the As impurity. For these centers we were able to observe an ${\mathrm{As}}^{75}$ hyperfine structure in the EPR spectrum. We determine from this hyperfine structure a value of $〈\frac{1}{r^3}〉=2.99\mathrm{}$ a.u. for the hole orbit around the As and a value for the nuclear electric quadrupole moment of ${\mathrm{As}}^{75}$, $q=0.28\mathrm{}$ b.