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This work reports on the formation of high-density (~1013–1014 cm−2) two-dimensional electron gas (2DEG) in ZnO-based heterostructures, grown by a dual ion beam sputtering system. We probe 2DEG in bilayer MgZnO/ZnO and capped ZnO/MgZnO/ZnO heterostructures utilizing MgZnO barrier layers with varying thickness and Mg content. The effect of the ZnO cap layer thickness on the ZnO/MgZnO/ZnO heterostructure is also studied. Hall measurements demonstrate that the addition of a 5 nm ZnO cap layer results in an enhancement of the 2DEG density by about 1.5 times compared to 1.11 1014 cm−2 for the uncapped bilayer heterostructure with the same 30 nm barrier thickness and 30 at.% Mg composition in the barrier layer. From the low-temperature Hall measurement, the sheet carrier concentration and mobility are both found to be independent of the temperature. The capacitance–voltage measurement suggests a carrier density of ~1020 cm−3, confined in 2DEG at the MgZnO/ZnO heterointerface. The results presented are significant for the optimization of 2DEG for the eventual realization of cost-effective and large-area MgZnO/ZnO-based high-electron-mobility transistors.

Well-crystalline ZnO nanoflowers were prepared by a facile solution process and their applications as an antimicrobial agent against Escherichia coli and enzyme-free glucose sensor have been studied. The morphological, structural, compositional, and optical properties of ZnO nanoflowers were characterized by various techniques, which confirmed the well-crystalline wurtzite hexagonal phase. The minimum inhibitory concentration of ZnO nanoflowers for inhibiting the growth of Escherichia coli was found to be 25 microg/ml. ZnO nanoflowers were also tested as an efficient electron mediator for the fabrication of highly sensitive non-enzymatic glucose sensor, which exhibited a high sensitivity of -411 microA M(-1) cm(-2) and detection limit of -1.25 mM with a quick response time of -10.0 s. The presented studies showed that ZnO nanomaterials can be efficiently used as an antimicrobial agent and a highly sensitive non-enzymatic glucose sensor.