The emission properties of Al2O3 coated Si field emitters were found to be radically different from any others reported to date, Silicon field emitter arrays were coated with ultrafine aluminum oxide powders by dielectrophoresis, The emission threshold, corresponding to a current of 10 pA, was 0.25 V/mm. The current-voltage (I-V) plots of the Al2O3 coated Si field emitter arrays were steep, with a distinct deviation from Fowler-Nordheim (F-N) behavior, The emission showed a slow but distinct increase or decrease of current with time depending on the magnitude of the current. This behavior could be approximated with an exponential function. We suggest a tentative explanation in terms of "field emission induced secondary electron emission", i.e. the generation of a secondary electron cascade by the interaction of the field emitted electrons with crystallites comprising the porous aluminum oxide coating. (C) 2002 Elsevier Science B.V. All rights reserved.