Niranjan S. Ramgir

Field emission studies of novel ZnO nanostructures in high and low field regions

A study of the field emission characteristics of novel structures of ZnO, namely marigolds, multipods and microbelts, has been carried out in both the close proximity configuration and the conventional field emission microscope. The use of a conventional field emission microscope overcomes the drawback of arc formation at high field values. The nonlinearity in the Fowler-Nordheim (F-N) plot, a characteristic feature of semiconductors has been observed and explained on the basis of electron emission from both the conduction and the valence bands. The current stability exhibited by these structures is also promising for future device applications.

Ultralow threshold field emission from a single multipod structure of ZnO

The field emission of individual ZnO multipods and a single arm of a multipod structure grown by a vapor deposition were carried out. A current of 1 nA with an ultralow onset voltage of 40 V was observed repeatedly for the single multipod as well as for the arm. The nonlinearity observed in the Fowler–Nordheim plots have been interpreted on the basis of the theory of electron emission from semiconductors and a scheme explaining the field emission behavior in both the high- and low-field regions owing to the very high geometrical factor has been picturized.

Selective growth of silica nanowires using an Au catalyst for optical recognition of interleukin-10

The vapor-liquid-solid (VLS) growth procedure has been extended for the selective growth of silica nanowires on SiO(2) layer by using Au as a catalyst. The nanowires were grown in an open tube furnace at 1100u2009°C for 60xa0min using Ar as a carrier gas. The average diameter of these bottom-up nucleated wires was found to be 200xa0nm. Transmission electron microscopy analysis indicates the amorphous nature of these nanoscale wires and suggests an Si-silica heterostructure. The localized silica nanowires have been used as an immunoassay template in the detection of interleukin-10 which is a lung cancer biomarker. Such a nanostructured platform offered a tenfold enhancement in the optical response, aiding the recognition of IL-10 in comparison to a bare silica substrate. The role of nanowires in the immunoassay was verified through the quenching behavior in the photoluminescence (PL) spectra. Two orders of reduction in PL intensity have been observed after completion of the immunoassay with significant quenching after executing every step of the protocol. The potential of this site-specific growth of silica nanowires on SiO(2) as a multi-modal biosensing platform has been discussed.

Energy analysis of field emitted electrons from a ZnO tetrapod

The experimental total energy distribution (TED) of the field emitted electrons from a single pod of a ZnO tetrapod has been obtained, exhibiting a two-peak feature. The energy difference between the two peaks in the TED is found to be nearly equal to the band gap of the bulk ZnO. The results show that field emitted electrons originate from both the conduction and valence bands. The peak position dependence on the applied voltage has also been observed. In the present case, the size of the ZnO tetrapod is not small enough to reflect the quantum confinement effects.

Enhanced Field Emission Characteristics of Novel ZnO Multipod Nanostructures

Summary form only given. Zinc oxide (ZnO), a wide band gap semiconductor has been widely exploited for its application in field emission based devices. It offers various advantages like strong excitonic binding energy (60 meV), negative electron affinity, and high mechanical strength making it a good candidate for field emitter arrays of flat panel display devices. However, most of the reports in literature deal with the field emission studies carried out in close proximity geometry, subject to a narrow range of applied voltage. Such type of experimental arrangement forbids the measurement at relatively higher field, as it may lead to an arc formation. The study of the field emission characteristics over a wide applied field range is critical to understand the physics at low dimensions. Moreover, the reason for the higher field enhancement and the appropriate relation of the geometry with the field emission characteristics is important and desirable. Accordingly, we have studied the field emission properties of various ZnO structures in both the configuration to elucidate the relation between morphology and geometry of emitter on the field emission behavior