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We report negative magnetoresistance in pulsed laser deposited single phase ZnO and Mg0.268Zn0.732O films and attribute it to the presence of oxygen interstitials (Oi) and zinc interstitials (Zni) as observed in the X-ray photoelectron spectra of the films. An interesting feature of reduction of negative magnetoresistance at low temperatures and large fields in Mg0.268Zn0.732O film is observed and is explained by taking into account the localized scattering.

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We report the change in the type of band alignments due to an increase in the dopant (Mg) concentration in pulsed laser deposited ZnO/MgZnO bilayer film. The band offset measurements were carried out from the core level shifts as well as valence band maxima in the single as well as the bilayer films. The change in the type of band alignment is attributed to the surface enrichment of Mg at the heterojunction.

The bottom-up integration of a 1D-2D hybrid semiconductor nanostructure into a vertical field-effect transistor (VFET) for use in flexible inorganic electronics is reported. Zinc oxide (ZnO) nanotubes on graphene film is used as an example. The VFET is fabricated by growing position- and dimension-controlled single crystal ZnO nanotubes vertically on a large graphene film. The graphene film, which acts as the substrate, provides a bottom electrical contact to the nanotubes. Due to the high quality of the single crystal ZnO nanotubes and the unique 1D device structure, the fabricated VFET exhibits excellent electrical characteristics. For example, it has a small subthreshold swing of 110 mV dec , a high I /I ratio of 10 , and a transconductance of 170 nS µm . The electrical characteristics of the nanotube VFETs are validated using 3D transport simulations. Furthermore, the nanotube VFETs fabricated on graphene films can be easily transferred onto flexible plastic substrates. The resulting components are reliable, exhibit high performance, and do not degrade significantly during testing.

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We report the effect of screw dislocations and oxygen vacancy defects on the optical nonlinear refraction response of ZnO films grown on a sapphire substrate at various oxygen flow rates using the chemical vapor deposition technique. The nonlinear refraction response was investigated in the off-resonant regime using a CW He-Ne laser source to examine the role of the intermediate bandgap states. It has been observed that the structural defects strongly influence the optical nonlinearity in the off-resonant regime. Nonlinearity has been found to improve as the oxygen flow rate is lowered from 2 sccm to 0.3 sccm. From photoluminescence studies, we observe that the enhanced defect density of the electronic defect levels due to the increased concentration of structural defects (with the decrease in the oxygen flow rate) is responsible for this improved optical nonlinearity along with the thermal effect. This suggests that defect engineering is an effective way to tailor the nonlinearity of ZnO films and their utility for optoelectronic device applications.

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