M. Takai

Superposition of fringelike-electron-emission pattern from radical-oxygen-gas exposed Pt field emitter fabricated by electron-beam-induced deposition

Electron-beam deposited Pt emitters were exposed to radical-oxygen gas to remove the surface amorphous carbon layers of the emitters, resulting in observation of fringelike-electron-emission patterns. The superposition of electron-wave interferences due to electrons emitted from a Pt emitter was further observed. These emission patterns were found to be well reproduced by the Fraunhofer diffraction model. These results suggested that the electron-wave interference might take place by electrons emitted from emission sites of Pt nanocrystals.

Relationship between field-emission characteristics and defects measured by Raman scattering in carbon-nanotube cathodes treated by plasma and laser

The relationship between field-emission characteristics and defects measured by Raman scattering for printed carbon-nanotube cathodes treated by plasma and laser was investigated. The Raman intensity ratio of the D to G bands (ID/IG) was 0.71 in the case of an untreated sample. With laser irradiation, the ID/IG ratio increased to 0.76, which resulted in the increase of the emission-current density. Moreover, with the plasma and additional laser treatment, the ID/IG ratio further increased to 1.15, which resulted in the much higher increase of the emission current density. This result indicates that the induced defects, acting as emission sites, together with the improved field-enhancement factor by the surface treatment, play important roles for increasing the field-emission current density.

Electron wave interference induced by electrons emitted from Pt field emitter fabricated by focused-ion-beam-induced deposition

Fringelike electron emission patterns emitted from Pt field emitters fabricated by focused-ion-beam-induced deposition (FIBID) were investigated by field-emission microscopy and in situ field-ion microscopy (FIM). The FIM image with electron emission sites showed adjacent two emission sites within a diameter of a Pt nanocrystal. These results indicate that the origin of fringelike electron emission patterns of Pt field emitters fabricated by FIBID are the electron wave interference induced by electrons emitted from adjacent two electron emission sites within a Pt nanocrystal.

Transmission-Electron-Microscopy Observation of Pt Pillar Fabricated by Electron-Beam-Induced Deposition

Pt pillars with a waist size of 20 nm and a length of 300 nm were fabricated by electron-beam-induced deposition and characterized by transmission electron microscopy before and after annealing or radical oxygen gas exposure. The average grain size of Pt nanocrystals was found to increase from 1.9?0.3 to 4.3?1.0 nm after annealing at 450 ?C. The Pt nanocrystals seem to coalesce with annealing. This result indicates that the change in the electron transport of Pt nanowires after annealing is due to the physical coalescence and the increase in the grain size of the Pt nanocrystals. The Pt nanocrystals were found to appear at the tip surface owing to the removal of the amorphous carbon matrix by radical oxygen gas exposure.

In situ transmission electron microscopy observation of electron-beam-deposited Pt field emitter during field emission and field evaporation

An internal structure of Pt field emitters fabricated by electron-beam-induced deposition (EBID) was investigated by in situ transmission electron microscopy during field emission and field evaporation. The internal structure of Pt field emitters was unchanged during field emission with an emission current of less than 480 nA. On the contrary, the top of Pt field emitters was sharpened after field evaporation. The Pt nanocrystals also moved to the Pt tip top after field evaporation. These results indicate the possibility of the sharpening of Pt field emitters by field evaporation, which would improve the field emission properties of Pt field emitters fabricated by EBID.

Electron Transport Properties of Pt Nanoarch Fabricated by Electron-Beam-Induced Deposition

Pt nanoarches were fabricated by electron-beam-induced deposition. The resistances of the nanoarches with oxygen-radical process, annealing in a furnace, and joule heating by current flow through the nanoarch were measured at room temperature and low temperatures to discuss the coherent electron field emission from the material. It is found that the resistance of the nanoarch increases by the oxygen-radical process and decreases by the current passing through the nanoarch due to the temperature rise. The decreased resistance should contribute to the coherent electron emission.

Electron-wave interference induced by electrons emitted from Pt field emitter fabricated by focused-ion-beam-induced deposition

The development of a coherent-field emitter for electron-wave interferences and its possible application have been investigated in our research. So far, electron-wave interferences induced by electrons emitted from a Pt field emitter fabricated by electron-beam-induced deposition (EBID) were reported.1,2 However, the field emission properties and electron-emission patterns of Pt field emitters fabricated by focused-ion beam (FIB)-induced deposition (FIBID) have not been characterized. The resistivity of a Pt nanowire fabricated by EBID was quite high and decreases by three to four orders of magnitude after annealing at 400° C.3,4 On the other hand, the resistivity of Pt nanowire deposited by FIB was very low even without annealing. The Pt field emitter fabricated by FIBID might be, therefore, more suited to the coherent-field emitter. In this study, the characteristics of Pt field emitters fabricated by FIBID and their electron-emission patterns of electron-wave interference were investigated.

In situ transmission-electron-microscope observation of electron-beam-deposited Pt field emitter under field emission and field evaporation

A coherent-field emitter for electron-wave interference has been investigated in our study. So far, electron-wave interferences were observed from the Pt field emitter fabricated by electron-beam-induced deposition (EBID).1 It has been suggested that the electron-wave interference takes place by electrons emitted from individual adjacent emission sites within a Pt nanocrystal.2 It was, however, unclear whether the electron beams were emitted from a Pt nanocrystals, because Pt layers fabricated by EBID were the composites of Pt nanocrystals and amorphous carbon matrix. Furthermore, the resistivity of EB-deposited Pt nanowire was found to be quite high (1 Ωcm) and decreases by three orders of magnitude after annealing at 400° C.3,4 The grain size of Pt nanocrystals was also found to increase by annealing.5 In our experiment, the emission current of more than 10 μA can be obtained from an EB-deposited Pt field emitter, although the as-deposited Pt field emitter has quite high resistance. The structure of Pt field emitters might be varied due to the Joule heating during field emission. In addition, the possibility for the control of emission sites by field evaporation will be investigated in order to fabricate the coherent-field emitter for electron-wave interference in our future experiment. Therefore, the clarification of the structural changes in Pt field emitters under field emission and field evaporation are important in order to develop the coherent-field emitter utilizing EB-deposited Pt. In this study, the structural changes in the EB-deposited Pt field emitter under field emission and field evaporation were investigated by in situ transmission-electron-microscope (TEM) observation.

Effect of radical oxygen gas exposure on Pt field emitter fabricated by electron-beam induced deposition

The fabrication process of Pt field emitters with tip radii less than 10 nm and gate diameters ranging from 100 to 800 nm using focused ion beam (FIB) induced physical sputtering and EBID was developed. However, the Pt field emitter fabricated by EBID has an inherent issue of leakage current between the gate and cathode electrode due to the unwanted deposition at a gate insulator sidewall. Therefore the generation mechanism of leakage current and the decrease of leakage current of field emitters by a post treatment with radical oxygen gas exposure were studied.

Improvement of emission efficiency of nanocrystalline silicon planar cathodes

In this paper, in order to improve the emission efficiency and understand the emission mechanism MOS cathodes are fabricated based on nanocrystalline Si (nc-Si) prepared by a pulsed laser ablation (PLA) technique and investigated their emission properties. The cathode is composed of nc-Si covered with a thin oxide film sandwiched between an n-type silicon substrate as an electron source and a thin top electrode. The emission area of the cathode was designed 500 mum in diameter. The emission characteristics of the nc-Si MOS cathode were measured in a vacuum of 10-5 pa.