Quantum Materials - 07

Abstract

Incorporating molecular quantum dots into a Si-based double-tunnel junction provides an effective way to integrate molecular functions into future CMOS technology for large-scale-integrated molecular devices.[1,2] In this work we have embedded magnetic molecules such as paramagnetic radical NN-TP and iron phthalocyanine (FePc) into a metal-oxide-semiconductor (MOS) structure (Figure 1a) to evaluate the quantum transport through their discrete molecular orbitals. The MOS structure acts as double-tunnel junction and constitutes a two-terminal molecular device. We observed sharp peaks in dI/dV curves at 7 K which indicates multilevel resonant tunneling through the discreate molecular orbitals of NN-TP radical. The resonant tunneling was observed even at 100 K. Moreover, resonant tunneling through singly occupied molecular orbital (SOMO) manifests the survival of the unpaired electron in the NN-TP radicals in the Si-based solid-state device (Figure 1b).
Resonant tunneling was also observed in FePc-based molecular devices at 7 K (Figure 1c). The interesting feature of FePc-based molecular devices is observation of resonant tunneling through the d-orbitals (d_z2 ) and d_xz/yz) of Fe atoms. The peak positions in dI/dV curves agree with previously reported experimental data of FePc using scanning tunneling spectroscopy (STS).[3] The quantum transport through Fe d-orbitals is crucial because the magnetic properties of FePc arise primarily from the unpaired electrons in the d-orbitals of the Fe atom.
Therefore, resonant tunneling through SOMO in purely organic radical NN-TP and d-orbitals of Fe in FePc molecules indicates that our approach has a great potential to integrate magnetic functionality into Si-based solid-state devices with CMOS compatibility for future molecular spintronics.