Mixed-Phase TiO₂ Nanotube–Nanorod Hybrid Arrays for Memory-Based Resistive Switching Devices

Metal oxide nanostructure hybrid materials have garnered focused attention for next-generation memory-based devices. TiO2 nanostructure hybrids dwell in that league of materials. In reference to that, the present work reports the growth of mixed-phase TiO2 nanostructures (MxPh-TNs) and their hybrids by grafting metal nanoparticles (MNPs). MxPh-TNs are a concoction of rutile nanorods and anatase nanotubes, imaged using field-emission scanning electron microscope and further confirmed by micro-Raman spectroscopy. During the growth of MxPh-TNs, a rutile and anatase mixed-phase interface is formed, as confirmed by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Furthermore, by grafting MNPs of platinum (Pt) and palladium–platinum (Pd–Pt) over MxPh-TNs, a top interface is investigated in order to have modifications in their structure and electronic interaction. Thus, dual interfaces corresponding to a mixed phase (rutile and anatase) and MNPs/TNs result in the modification of formed nanostructures and their hybrids (MX-TNHs), as confirmed by X-ray photoelectron spectroscopy and Kelvin probe force microscopy (KPFM) studies. Modification at the interface results in improved crystallinity and symmetric barriers for charge transport in hybrid structures. MxPh-TNs and MX-TNHs are further explored for device applications in the form of memristive resistive switching devices. It is observed that the device performances of Pt/MX-TNHs and Pd–Pt/MX-TNHs are better than that of MxPh-TNs in terms of the memory window (ION/IOFF ratio). The improved device performance in the hybrid structures are due to the enhanced charge separation and defects at the interface of MNPs (Pt and Pd–Pt) and MxPh-TNs.