@article { ISI:000271238900027, title = {Field emission properties of Al-doped ZnO nanostructures}, journal = {Journal of Nano Research}, volume = {5}, year = {2009}, month = {JAN}, pages = {231-237}, publisher = {TRANS TECH PUBLICATIONS LTD}, address = {LAUBISRUTISTR 24, STAFA-ZUERICH, CH-8712, SWITZERLAND}, abstract = {

Field emission from Al-doped ZnO nanostrcutures has been investigated in planar diode configuration under ultra high vacuum conditions. The Al-doped ZnO nanostructures were synthesized by co-precipitation method with varying aluminium concentrations. The as- synthesized product was characterized by x-ray diffraction, scanning electron microscope and energy dispersive x-ray analysis. The threshold field required to draw a current density of similar to 1 mu A/cm(2) was observed to be similar to 2.0 V/mu m and similar to 2.3 V/mu m for Al-doped ZnO nanostructures synthesized with aluminium concentrations of 1\% and 3\%, respectively. The Fowler- Nordheim (F-N) plots for both the specimens exhibit non-linear behaviour, which is observed to be specimen dependent. The nonlinearity observed in the F-N plots has been interpreted on the basis of the theory of electron emission from semiconductor emitters. The field enhancement factors, estimated from the slope of the F-N plots, are found to be similar to 9.3 x 10(3) and 3.9 x 10(3) for 1\% and 3\% Al-doped ZnO emitters, respectively. The high values of the field enhancement factor Suggest that the emission is from the nanostructures. The emission current stability measured at the preset value of similar to 2 mu A over a period of more than three hours is found to be fairly stable. The results indicate use of Al-doped ZnO nanostructures as promising emitters for field emission based devices.

}, keywords = {field emission, Fowler-Nordheim plots, Nanostructures, ZnO}, issn = {1662-5250}, author = {Navale, Shalaka C. and Sheini, Farid Jamali and Patil, Sandip S. and Mulla, Imtiaz S. and Joag, Dilip S. and More, Mahendra A. and Gosavi, Suresh W.} } @article { ISI:000283453700016, title = {Fowler-nordheim plot behavior and mechanism of field electron emission from ZnO tetrapod structures }, journal = {ACS Nano}, volume = {4}, number = {10}, year = {2010}, month = {OCT}, pages = {5585-5590}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Field emission measurements of current-voltage characteristics are reported for tetrapod structures of ZnO. The nonlinear Fowler-Nordheim (FN) plot is analyzed according to a model of calculation based on saturation of conduction band current and predominance of valence band current at high-field values. The simulated FN plot exhibits similar features to those observed experimentally. The model of calculation suggests that the slope variation of the FN plot, in the high-field and low-field regions, does not depend on the magnitude of saturation. Instead, it is a characteristic of the energy band structure and voltage-to-barrier-field conversion factor of the emitting material.

}, keywords = {field emission, Fowler-Nordheim plot, Nanostructures, nonlinearity, ZnO}, issn = {1936-0851}, doi = {10.1021/nn1008403}, author = {Al-Tabbakh, Ahmed A. and More, Mahendra A. and Joag, Dilip S. and Mulla, Imtiaz S. and Pillai, Vijayamohanan K.} } @article { ISI:000291725100012, title = {Synthesis of Cu-ZnO and C-ZnO nanoneedle arrays on zinc foil by low temperature oxidation route: effect of buffer layers on growth, optical and field emission properties}, journal = {Applied Surface Science}, volume = {257}, number = {20}, year = {2011}, month = {AUG}, pages = {8366-8372}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 degrees C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of similar to 100 mu A/cm(2), is observed to be 2.25 V/mu m and 1.57 V/mu m for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of similar to 100 mu A over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications. (C) 2011 Elsevier B. V. All rights reserved.

}, keywords = {Buffer layer, Carbon, Copper, field emission, Nanoneedle, ZnO}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2011.04.023}, author = {Jamali-Sheini, Farid and Patil, K. R. and Joag, Dilip S. and More, Mahendra A.} }