Abstract
Spintronics is one of the most exciting applications of graphene-based devices. In this work Density Functional Theory is used to study a nanojunction consisting of two semi-infinite graphene electrodes contacted with an iron-porphyrin (FeP) molecule, which plays the role of spin filter for the incoming unpolarized electrons. The graphene-FeP contact closely resembles the recently synthesized porphyrin-decorated graphene [He et al., Nat. Chem. 2017, 9, 33–38]. The analysis of the spectral properties of the system shows a variation of the orbital occupancy with respect to the isolated FeP molecule and an hybridization with the delocalized states of the substrate, while the overall magnetic moment remains unchanged. Doping the electrodes with boron or nitrogen atoms induces a relevant rearrangement in the electronic structure of the junction. Upon B doping the current becomes significantly spin polarized, while N doping induces a marked Negative Differential Resistivity effect. We have also investigated the possible exploitation of the FeP junction as a gas sensor device. We demonstrate that the interaction of CO and O2 molecules with the Fe atom, while being strong enough to be stable at room temperature (2.0 eV and 1.1 eV, respectively), induces only minor effects on the electronic properties of the junction. Interestingly, a quenching of the spin polarization of the current is observed in the B-doped system.
Highlights
In 1974, Aviram and Ratner proposed for the first time the use of an organic molecule contacting two electrodes as a current rectifier [1]
We study the structural, electronic and spin-dependent transport properties of a molecular junction composed of a single iron-porphyrin molecule contacted with two graphene electrodes
Either upon adsorption of O2 and CO the minority spin component of the current is largely enhanced, and it becomes very similar to the majority spin component. This means that spin polarization of the current, which in the pristine junction ranges from 25% to 50%, is almost completely quenched upon molecules adsorption, disclosing the possibility to build up spintronic nanosensors based on a graphene-FeP junction
Summary
In 1974, Aviram and Ratner proposed for the first time the use of an organic molecule contacting two electrodes as a current rectifier [1]. In 2017 the covalent linking of a single porphine to graphene edges was experimentally observed for the first time through scanning probe techniques with submolecular resolution [28], stimulating the efforts of both theoreticians and experimental researchers towards organic spintronic nanodevices [5,29] In this context, we study the structural, electronic and spin-dependent transport properties of a molecular junction composed of a single iron-porphyrin molecule contacted with two graphene electrodes. To get over these issues a huge research is under way to obtain sensors which are stable, selective, highly sensitive and with a quick response mechanism In this regard, an increasing number of theoretical and experimental studies have demonstrated that nanoengineered devices and materials are the key to reach the desired target [35,36]. To offer a throughout analysis of the potential performance of this device we considered the cases of undoped, B-doped and N-doped graphene electrodes
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