Dinuclear Aluminum Complex as an Active Material for RRAM Switching Device

Abstract

In this paper, we report the synthesis and structural characterization of dinuclear aluminum complex 1, containing redox-active bis-catecholaldimine ligand 6,6'-{[Ethane-1,2-diylbis(azanylidene)]bis(methanylidene)}-bis(3,5-di-tert-butyl-1,2-dihydroxybenzene) (LH4). Complex 1 was readily obtained by refluxing (LH4) and Al(NO3)3.9H2O in 3:2 molar ratio in the presence of triethylamine in a methanolic solution. Single-crystal X-ray diffraction analysis of complex 1 shows that catecholaldimine ligands bind through octahedral coordination to each of the two Al (III) centers. Out of three, two ligands are coordinating in a salen N2O2 fashion providing four coordinating sites while third ligand is acting as bridged ligand binding through its two catecholate oxygen atoms to each of the two Al (III) centers. Complex 1 was also further characterized by various techniques such as HRMS, FTIR, TGA and CHN analysis. The electrochemical characterization of complex 1 was done by cyclic voltammetry in DCM solution which shows several quasi-reversible and irreversible oxidation-reduction peaks. The lipophilic aluminum complex 1 was further employed as an active material to fabricate a resistive switching memory device, ITO/Complex 1/Ag, and characterized using the write-read-erase-read cycle. The device has interestingly shown a stable current–voltage characteristics, excellent endurance stability and analog switching between two different resistance states for 5000 s, making it a viable option for long-term data storage applications. The frontier molecular orbitals energy of complex 1 was calculated using density functional theory where it was observed that the hole injection is favourable during conduction mechanism of the memory device.