• L M Kukreja

      Articles written in Bulletin of Materials Science

    • Studies on nonvolatile resistance memory switching in ZnO thin films

      L M Kukreja A K Das P Misra

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      Six decades of research on ZnO has recently sprouted a new branch in the domain of resistive random access memories. Highly resistive and c-axis oriented ZnO thin films were grown by us using d.c. discharge assisted pulsed laser deposition on Pt/Ti/SiO2/Si substrates at room temperature. The resistive switching characteristics of these films were studied in the top-bottom configuration using current–voltage measurements at room temperature. Reliable and repeated switching of the resistance of ZnO thin films was obtained between two well defined states of high and low resistance with a narrow dispersion and small switching voltages. Resistance ratios of the high resistance state to low resistance state were found to be in the range of 2–5 orders of magnitude up to 20 test cycles. The conduction mechanism was found to be dominated by the Ohmic behaviour in low resistance states, while Poole–Frenkel emission was found to dominate in high resistance state. The achieved characteristics of the resistive switching in ZnO thin films seem to be promising for nonvolatile memory applications.

    • Self-assembled flower-like nanostructures of InN and GaN grown by plasma-assisted molecular beam epitaxy

      Mahesh Kumar T N Bhat M K Rajpalke B Roul P Misra L M Kukreja Neeraj Sinha A T Kalghatgi S B Krupanidhi

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      Nanosized hexagonal InN flower-like structures were fabricated by droplet epitaxy on GaN/Si(111) and GaN flower-like nanostructure fabricated directly on Si(111) substrate using radio frequency plasma-assisted molecular beam epitaxy. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the crystallinity and morphology of the nanostructures. Moreover, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to investigate the chemical compositions and optical properties of nano-flowers, respectively. Activation energy of free exciton transitions in GaN nano-flowers was derived to be ∼ 28.5 meV from the temperature dependent PL studies. The formation process of nanoflowers is investigated and a qualitative mechanism is proposed.

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