Ashok B. Bhise

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.

A single In-doped SnO2 submicrometre sized wire as a field emitter

Indium doped tin oxide submicrometre sized wires have been synthesized by thermal evaporation and characterized by field emission (FE) microscopy. The non-linear Fowler?Nordheim plot corresponds to the typical semiconducting behaviour of the emitter. The field enhancement factor has been estimated to be 29?900?cm?1 indicating that electron emission is due to the nanometric features of the emitter. A current density of the order of 6.36 ? 103?A?cm?2 with an applied electric field of 1 ? 104?V??m?1 has been obtained. The long term FE current stability tested at the preset current level of 1??A exhibits no severe fluctuations.

Stability of field emission current from porous n-GaAs(110)

Field electron emission from porous GaAs has been investigated. The emitter was prepared by anodic etching of n-GaAs (110) in 0.1 M HCl solution. The as-etched porous GaAs shows nonlinear Fowler–Nordheim (FN) characteristics, with a low onset voltage. The emitter, after operating for 6 h at the residual gas pressure of 1×10−8 mbar, shows a linear FN characteristics with a relatively high onset voltage and poor field emission current stability as compared to the as-etched emitter. The change in the behavior was attributed to the residual gas ion bombardment during field electron emission. X-ray photoelectron spectroscopic investigations were carried out on as-etched sample and the one which was studied for field emission. The studies indicate that the as-etched surface contains As2O3 and the surface after field electron emission for about 6 h becomes gallium rich. The presence of As2O3 seems to be a desirable feature for the stable field emission current.

Fabrication of In-doped SnO2 nanowire arrays and its field emission investigations

The field emission of In-doped SnO2 wire array has been performed in parallel plate diode configuration. A maximum current density of 60 µA/cm2 is drawn from the emitter at an applied field of 4 V/µm. The nonlinearity in the Fowler–Nordheim plot, characteristics of semiconductor emitter has been observed and explained on the basis of electron emission from both the conduction and the valence bands. The current stability recorded at a preset value of 1 µA is observed to be good. The high emission current density, good current stability and mechanically robust nature of the wires offer unprecedented advantages as promising cold cathodes for many potential applications based on field emission.

RuO 2 doped SnO 2 thin film on tungsten tip and its field emission

Nanocrystalline RuO2 doped SnO2 thin film has been synthesized by thermal evaporation on tungsten tip. The surface morphology of the as deposited thin film on tungsten tip has been characterized by SEM. The SEM studies reveal the complete required to draw an emission current of 1nA was observed to be 2 kV. An emission current density of the order of 8.9 A/cm2 has been obtained at an applied voltage of 7.5 kV. The Fowler-Nordheim plot show linear nature typically that of metal. The field enhancement factor estimated from the slope of F-N plot is 11260 cm-1, indicating that the electron emission from nanometric features of the emitter. The current stability recorded at preset value of 1 A/cm2 is observed to be promising with fluctuations less than 5 % of the stabilized current value. Our results on field emission from RuO2:SnO2 thin film on tungsten tip indicates that, it is a potential candidate for field emission based flat panel display devices, cold cathode electron sources, and in large area electronics devices.

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