Department of Physics
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Item Highly repeatable multilevel resistive switching characteristics of an Au/TiO 2 /Ti memory device(IOP, 2013) Gupta, Raj Kumar; Hazra, ArnabDevelopment of a highly repeatable multilevel resistive switching Au/TiO2/Ti memory device is reported in this paper. Undoped rutile TiO2 thin film, having a thickness of 480 nm, was grown on high-purity Ti (99.5%) by in situ thermal oxidation technique at 600 °C. Au metal contact was used as a top electrode. The developed Au/TiO2/Ti memory device was electrically characterized for resistive random access memory applications and found to have extremely repeatable, reproducible and stable bipolar resistive switching characteristics. With very low 'SET' and 'RESET' voltage requirement, the device offered highly symmetric multilevel high- to low-resistance state transitions. The two pairs of 'SET' and 'RESET' voltages were ±0.26 V and ±0.64 V. As there is no requirement of electroforming voltages, low electric field operation of the device is ensured, which eventually leads to the avoidance of high field hazards. The effect of operating temperature on the performance of Au/TiO2/Ti memory devices was also investigated in the temperature range of 27–80 °C, and the device offered negligible shift in the characteristics, ensuring high-temperature stability. The multilevel switching phenomenon was explained by appropriate defect models.Item Ultrathin Films of TiO2 Nanoparticles at Interfaces(ACS, 2015-01) Gupta, Raj Kumar; Manjuladevi, V.; Hazra, ArnabThe properties of a material change remarkably as a result of the scaling dimensions. The Langmuir–Blodgett (LB) film deposition technique is known to offer precise control over the film thickness and the interparticle separation. To form a well-ordered LB film, it is essential to form a stable Langmuir film at the air–water interface. Here, we report our studies on ultrathin films of TiO2 nanoparticles at air–water and air–solid interfaces. The Langmuir film of TiO2 nanoparticles at the air–water interface was found to be very stable, and it exhibits loose-packing and close-packing phases. The LB films were transferred onto solid substrates for characterization and application. The surface morphology of the LB film was obtained by a field emission scanning electron microscope. The optical and electronic properties of the LB films of TiO2 nanoparticles were studied using UV–vis spectroscopy and current–voltage measurements, respectively. The LB film of TiO2 nanoparticles was employed for ethanol gas sensing, and the sensing performance was compared to that of bulk material. Because of the enormous gain in the surface to volume ratio and the increase in crystalline defect density in the ultrathin LB film of TiO2 nanoparticles, the LB film is found to be a potential functional layer for ethanol sensing as compared to the bulk material.