The influence of different types of covering on electron field emission from silicon tips has been studied. For this a series of silicon tip array structures, namely (i) structures with porous silicon layers on the tops of the tips, (ii) tips covered with carbon films, (iii) silicon tips implanted by hydrogen, and (iv) cesium-enriched silicon tips, has been prepared and investigated. The comparison and characterization of various structures using effective work functions, field enhancement factors, and effective emission areas obtained from Fowler - Nordheim plots have been performed. Models and mechanisms of enhancement of the electron field emission have been proposed.

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The influence of the diamond-like carbon ͑DLC͒ films deposited in different conditions on electron field emission of silicon tips has been investigated. Arrays of square based pyramidal cathodes were fabricated in n-type Si͑100͒ using wet etching in an acid mixture. Undoped and nitrogen doped DLC films were grown by plasma enhanced chemical vapor deposition method from CH 4 :H 2 and CH 4 :H 2 :N 2 gas mixtures, correspondingly. During nitrogen doped DLC films deposition the nitrogen content in gas mixture was varied from 0% to 45%. The DLC films thickness was changed in range from 10 to 100 nm. Refractive indexes of DLC films were lower for thinner layers. The effect of preparation conditions of the DLC films on their electron emission properties ͑work function, threshold voltage, etc.͒ has been studied. For comparison of the emission properties of the structures with DLC films deposited in different conditions the threshold ͑onset͒ voltages, field enhancement factors, effective emission areas, calculated from Fowler-Nordheim plots, have been used. It was confirmed that for DLC coatings the electron field emission was substantially increased in comparison with the emission from silicon tips without the coatings, although the nonmonotonous dependence of effective work function on the refractive index of DLC films has been observed. In this context, optimization experiments with respect to the minimal value of the effective work function, which in some cases was less than 1 eV, have been performed. It was found that for the structures with nitrogen doped DLC films the emission appears at lower voltages and the calculated effective work function is 0.1 eV less than for case of the best undoped DLC films. The obtained results can be used for the development of the high efficient field emission cathodes. The model for explanation of the experimental results is presented and the role of carbon-carbon, carbon-hydrogen, and carbon-nitrogen bonds is discussed.

Effect of annealing charge injection and electron beam irradation of the Si-SiO2 interface barrier heights and on the work function difference in MOS structures AIP Conf.Silicon field emitter arrays have been fabricated and investigated. Four different field emission enhancement layers were studied: ͑1͒ porous silicon layers, ͑2͒ carbon films, ͑3͒ hydrogen implanted layers, ͑4͒ Cs-enriched layers. Scanning electron microscopy was used to study the morphology of the tips. Comparison of the above arrays was accomplished by obtaining effective work functions, field enhancement factors, and effective emission areas from Fowler-Nordheim plots.

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