Electron Paramagnetic Resonance of Alkali Metal Atoms and Dimerson Ultrathin MgO br

Electron paramagnetic resonance (EPR) canprovide unique insight into the chemical structure and magneticproperties of dopants in oxide and semiconducting materials thatare of interest for applications in electronics, catalysis, andquantum sensing. Here, we demonstrate that EPR in combinationwith scanning tunneling microscopy (STM) allows for probing thebonding and charge state of alkali metal atoms on an ultrathinmagnesium oxide layer on a Ag substrate. We observe a magneticmoment of 1 mu Bfor Li2, LiNa, and Na2dimers corresponding tospin radicals with a charge state of +1e. Single alkali atoms have thesame charge state and no magnetic moment. The ionization of theadsorbates is attributed to charge transfer through the oxide to themetal substrate. Our work highlights the potential of EPR-STM toprovide insight into dopant atoms that are relevant for the control of the electrical properties of surfaces and nanodevices