Spin Dependent Chemisorption Interactions at Metal-Organic Semiconductor Interfaces

Spin dependent electronic structure at interfaces can control spin injection efficiency in spintronic devices. Organic spintronics focused on spin polarized interface state formation due to hybridization between molecular orbitals and metallic band states [1]. This talk will describe observation of spin-polarized hybrid states at metal organic interfaces for organic semiconductor adsorbates with different adsorption interactions. Specific attention is payed to the metal quinolate molecules (Mq3’s) that have been a long-time focus of the organic spintronics community. Spin polarized scanning tunneling microscopy and spectroscopy studies of Mq3’s (where M is either Al or Cr) show hybridization with a magnetic surface state on the Cr(001) surface that varies significantly for the different molecules resulting in either metallic or resistive interface states [2]. Subtle differences in adsorption interactions lead to large differences in the spin-dependent electronic structure at the interface. First principles calculations have provided specific microscopic rationale to the observed diversity of interface states in terms of binding geometry and distances. In addition, the variations can be viewed within the model framework of the Anderson-Newns-Grimley model of chemisorption [3]. This convergence of observation, first-principles computations, and model-based understanding shows that molecular treatment of magnetic electrodes can be a reasonably rational approach to optimizing spin injection in the full range of spintronic applications.
[1] Cinchetti et al., Nat. Mater. 16, 507 (2017).
[2] Wang et al., Phys. Rev. B 95, 241410R (2017).
[3] Newns Phys. Rev. 178, 1123 (1969).