Abstract
Metallocenes are a promising candidate for future spintronic devices due to their versatile and tunable magnetic properties. However, single metallocenes, e.g., ferrocene, sublimate below room temperature, and therefore the implementation for future applications is challenging. Here, a method to prepare biferrocene thin films using organic molecular beam deposition (OMBD) is presented, and the effect of substrate and deposition rate on the film structure and morphology as well as its chemical and magnetic properties is investigated. On Kapton and Si substrates, biferrocene interacts only weakly with the substrate, and distinct grains scattered over the surface are observed. By incorporating a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) seeding layer and depositing biferrocene at high deposition rates of 1.0 Å s–1, it is possible to achieve a well-ordered densely packed film. With spintronic applications in mind, the magnetic properties of the thin films are characterized using superconducting quantum interference device (SQUID) magnetometry. Whereas initial SQUID measurements show weak ferromagnetic behavior up to room temperature due to oxidized molecule fragments, measurements of biferrocene on PTCDA capped with LiF show the diamagnetic behavior expected of biferrocene. Through the successful deposition of biferrocene thin films and the ability to control the spin state, these results demonstrate a first step toward metallocene-based spintronics.
Highlights
With the first synthesis of ferrocene in the early 1950s by Kealy and Pauson,[1] and independently by Miller, Tebboth and Tremaine[2] a new class of molecules was born
We have demonstrated the successful deposition at room temperature of biferrocene thin films on different substrates via thermal sublimation
The iron oxide was observed via the ferromagnetic behaviour in the superconducting quantum interference device (SQUID) measurements of biferrocene on Kapton
Summary
With the first synthesis of ferrocene in the early 1950s by Kealy and Pauson,[1] and independently by Miller, Tebboth and Tremaine[2] a new class of molecules was born. Special interest in metallocenes arose within the field of spintronics after theoretical studies showed that ferrocene wires possess the ability to generate a nearly 100% spin-polarized current.[13] theoretical studies conducted on bicobaltocene and binickelocene showed spinfiltering properties,[14] and current rectification is predicted for nickelocenylferrocene.[15] Simulations carried out on ferrocene deposited on pristine graphene nanoribbons showed a possible spin valve structure that could generate a perfect magnetoresistive effect.[16] using STM it was demonstrated that nickelocene maintains its spin on metallic surfaces.[17] metallocenes are promising candidates for the realisation of future organic spintronic devices and quantum computing. With the ability to control the spin state of bimetallocene molecules via oxidation and selecting the magnetic properties via a suitable choice of the metal centre, the successful deposition of biferrocene molecules shows great potential towards metallocene-based spintronic devices
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