Akihiko Hosono

Maskless fabrication of field-emitter array by focused ion and electron beam

Niobium-gated field-emitter arrays with Pt tips were fabricated using focused ion and electron beams. A promising approach, based on a two-step etch process in a Nb/SiO2/Si structure, has been implemented for the suppression of beam-induced damage and contamination in the processed area during the production of the gate openings. Only the top Nb layer was removed for gate openings by physical sputtering using the focused ion beam. The underlying SiO2 was subsequently removed by wet etching. Deposition of Pt pillars into these gate openings using electron-beam-induced chemical reaction resulted in field emission at an applied gate bias of 50 V even without any thermal annealing process.

High emission current double-gated field emitter arrays

Recently, various types of the field emitter arrays (FEAs) with focusing gate were investigated to realize the focusing electron beam. However, it is difficult to realize the high emission current density at the focusing operation. So we investigated to realize the high emission current density at the focusing operation.

Modification of field emitter array tip shape by focused ion‐beam irradiation

Tip shapes of Si field emitter arrays, fabricated by a conventional dry etching process, have been modified by focused ion‐beam (FIB) irradiation to obtain a sharp cone shape. Flat‐topped Si tips could be sharpened by localized sputtering using FIBs for a short time. Tip shape inspections and repairs were also performed using a FIB system combined with an electron‐beam column to remove metal residues and melted emitters.

Field emitter array fabricated using focused ion and electron beam induced reaction

A dual beam system consisting of focused ion and electron beams was used for manufacturing of Nb-gated silicon field emitter arrays. Gate opening was produced either by reactive focused ion beam etching of both the niobium and the silicon dioxide layer or by physical sputtering of the niobium layer by focused ion beam and subsequent wet etching of the underlying silicon dioxide layer. Platinum tips were deposited into the gate opening using an electron beam induced chemical reaction. Prototype devices, which exhibit field emission, were produced successfully. Several process parameters such as ion dose, beam diameter, and etch duration were systematically varied to identify the optimum condition for the fabrication of field emitter arrays.

Fabrication of field emitter array using focused ion and electron beam induced reaction

A 30 keV dual beam system with focused ion and electron beams has been used to develop a fast fabrication process of field emitter arrays (FEAs). The gate opening was fabricated by reactive focused ion beam etching. Pt cathode tips were deposited through gate opening using electron beam induced chemical reaction. Pt tips fabricated in the over-etched Si FEA showed field emission. A prototype of a nanometer-sized FEA was fabricated using a dual beam technique with FIB etching and electron beam induced deposition.

Laser cleaning of field emitter arrays for enhanced electron emission

The effect of laser irradiation on the electron emission efficiency of field emitter arrays has been investigated as a function of wavelength using different harmonics of a diode-pumped Nd:YLF laser. While irradiation in the infrared or visible range did not induce any observable change in the emission behavior, ultraviolet laser irradiation, even at a lower fluence compared to infrared or visible, resulted in a significant increase of the emission efficiency, revealing that the photodecomposition of organic contaminants is the main mechanism for cleaning. During laser irradiation, the emission current increases gradually, approaching a saturation level as the surface is cleaned.

Fabrication process of field emitter arrays using focused ion and electron beam induced reaction

Metal-gated Pt field emitter arrays (FEAs) have been manufactured using a dual beam system consisting of focused ion and electron beams. The gate opening in Nb or Au gate layers was produced by physical sputtering using a focused ion beam and subsequent wet etching of the underlying silicon dioxide layer. Deposition of a platinum tip into the gate opening using electron-beam-induced chemical reaction resulted in field emission without any thermal annealing process. After wet etching an enlargement of the gate opening in Nb-gated FEAs was observed due to the beam-induced enhanced etching. In contrast, the smaller gate opening in Au-gated FEAs was easily fabricated because of the suppression of the enhanced etching. Consequently, the gate opening was controlled by selection of the gate metal material. The turn-on voltage for field emission decreased by decreasing the diameter of the gate opening.

Electron-Beam-Induced Deposition of Pt for Field Emitter Arrays

Pt emitters were deposited using electron-beam-induced reaction on overetched Si emitters fabricated by a conventional dry etching process. An emission current of 10 µA was obtained from a 100-tip field emitter array (FEA) at an extraction voltage of 100 V. A prototype of a nanometer-sized field emitter was fabricated using focused ion beam (FIB) etching and electron-beam-induced deposition (EBID).

Electron emission from gated silicide field emitter arrays

Silicidation of the top surface of Si tips with a Nb gate structure has been carried out to improve the emission behavior of Si field emitter arrays (FEAs). A Pt layer with a thickness of 5–10 nm was deposited through the gate opening and annealed at 850 °C. The electron emission was enhanced by a factor of 10 and the average emission per tip was 3.5 μA for a 10×10 FEA. Fowler–Nordheim plots indicated the decrease in work function after silicidation.

Emission characteristics of printed carbon nanotube cathodes after laser treatment

Recently, field emission displays using printed carbon nanotubes (CNTs) as an emitter have been researched eagerly. By laser irradiation, some CNTs in the printed CNT layer stand out, and they work as the emission sites. We found that the higher CNTs that are easier to be the emission sites tend to exist at the boundary of the laser irradiation pattern. We used the irradiation patterns that consist of the arrays of microirradiation pattern to increase the total length of boundary. Both emission characteristics and emission uniformity were improved by the increase of the boundary length. We examined several lasers, and the irradiation by the second harmonic generation yttrium aluminum garnet laser of which wavelength was greatest in our experiment provided the best emission characteristics (turn-on electric field <2V∕μm) and emission uniformity (turn-on electric field deviation <5%).