Tip Field Emitter Arrays Research Articles

Field emission characterization of nanoFEAs on single crystal CeB6 surface fabricated by focused ion beam milling

The field emission tip arrays with sub-100 nm apices (nanoFEAs) on single crystal cerium hexaboride (CeB6) surface were fabricated by the focused ion beam (FIB) milling microtechnology. The surface morphologies and field emissions of the nanoFEAs are systematically characterized. FIB milling, similar to the physical stripping process, can fabricate the nanoFEAs single crystal CeB6 with uniform morphologies. The nanoFEAs with sharp tips of size about 50 nm demonstrate the lowest turn-on electric fields (2.0 V/[Formula: see text]m), as well as a high current ([Formula: see text]1 mA) at the field of 6.7 V/[Formula: see text]m and a high stable emission current. Such excellent performances make CeB6 nanoFEAs promising candidates for application in field emission electronics.

Femtosecond laser processing and field emission properties of the FEAs on single crystal GdB6 (100) surface

The single crystal GdB6 were prepared by optical zone melting method. Moreover, using the femtosecond laser micromachining technology processed the field-emission tip arrays (FEAs) on the (100) surface of single crystal GdB6. The single crystal quality, field emission of the FEAs, as well as the electronic structure of single crystal GdB6 are systematically characterized. The quality of single crystal is good. The curvature radius of the produced FEAs with uniform morphology and undamaged crystal surface structure are about 0.5 μm. The FEAs showed good field emission performance, which the turn-on electric field of the FEAs is 2.6 V/μm with a field emission current of 0.46 A/cm2 at 7.3 V/μm and the emission current has high stability. The calculation electronic structure of GdB6 show that the 5d electron of Gd determines the electronic state of excellent emission performance. The high electric field will greatly decrease the surface barrier and work function of GdB6, according with the field emission theory.

The femtosecond laser micro-processing of the field-emission tip arrays in single crystal CeB6

The field-emission tip arrays (FEAs) in single crystal cerium-hexaboride (CeB6) were micro-processed by femtosecond laser. The results show that the femtosecond laser has no damage to the surface structure and phase of the CeB6 FEAs, and the FEA with the curvature radius of the optimal tips of about 0.6 μm and the height of about 5 μm have uniform morphology and the best field-emission performance. The single crystal CeB6 FEAs had good emission stability under the following conditions: the starting electric field of 2.8 V/μm and an emission current density of 0.98 A/cm2 at an electric field of 7.7 V/μm. The calculations of material removal threshold and finite element simulation of the temperature field substantiate that laser peak energy density F0=0.95 J/cm2 is in good agreement with the theoretical calculation result (0.51 J/cm2≤F0 ≤ 2.12 J/cm2). Finally, the best process parameter range of this experiment is obtained. These results further indicating that the femtosecond laser micro-processing is an effective method to develop the vacuum field-emission application of single crystal CeB6.

Field emission investigations of single crystal LaB6 FEA fabricated by femtosecond laser direct writing

The femtosecond laser direct writing method has been used to fabricate the single crystal lanthanum hexaboride (LaB6) field-emission tip arrays (FEAs). The morphologies, structure phase, and field emission of the single crystal LaB6 FEAs are systematically studied. The nanostructures on the surface of tips with the LaB6 phase were formed, resulting in favor of improving field emission, particularly for samples with the nanohill shaped bulges having the size of about 100 nm. The produced single crystal LaB6 FEAs have a uniform structure and a controllable curvature radius of about 0.5–3.0 μm. The FEAs with a curvature radius of about 0.5 μm as field emitters have the best field emission performance, which the field emission turns on and the threshold electric fields are as low as 2.2 and 3.8 V/μm with an emission current of 1.0 A/cm2 at 8.0 V/μm, and the emission current exhibits high stability. These indicate that the processed LaB6 FEAs have a good prospect applied in vacuum microelectronic devices and the simple femtosecond laser direct writing method could lead to an approach for the development of electron sources.

A Method to Fabricate Field Emission Tip Arrays by Electrocodeposition of Single-Wall Carbon Nanotubes and Nickel

A new method to fabricate carbon nanotube field emission structure is developed. The emitter structure is a composite of single-wall carbon nanotubes (SWNTs) and Ni, and this is done by codepositing SWNTs and Ni metal via electrolysis. The carbon nanotubes distributed in the Ni matrix show a strong contact with the substrate. To enable good dispersion of the SWNTs in the conventional Ni Watt bath solution which is required for uniform codeposition, several techniques are successfully employed, i.e., oxidation and heat-treatment of the carbon nanotubes, surfactant coating, ultrasonic agitation, etc. A post chemical etching process is also necessary to enhance the emission properties. The emission is uniform, and the current density reached 1.2 mA/cm 2 at 4 V/μm.

HYDROGEN-FREE DIAMOND-LIKE CARBON DEPOSITED BY A LAYER-BY-LAYER TECHNIQUE USING PECVD

We developed a hydrogen-free diamond like carbon (DLC) film by a novel deposition technique of a layer-by-layer technique using plasma enhanced chemical vapor deposition (PECVD) in which a repeated deposition of a thin DLC layer and subsequently CF 4 plasma treatment on its surface have been carried out. The electrical, optical and structural properties of the DLC films deposited depend on the CF 4 plasma exposure time. The hydrogen content is less than 1 at % when the CF4 plasma exposure time is 140s. Its emission current is much higher and stability is much improved compared with conventional DLC.N-type, hydrogen-free DLC could be obtained by N ion doping N2 gas-phase doping in the CF 4 plasma. The optimum [ N 2][ CH 4] flow rate was found to be 9% for the efficient electron emission, at which the onset-field was 7.2 V /μ. The nitrogen gas-phase doped hydrogen-free DLC coating on Mo tip field emitter arrays (FEAs) increased the electron emission current from 160μ A to 1.52 mA and improved the stability in electron emission current.

The Influence of Gate Insulator Etching on the Characteristics of Mo Tip Field Emitter Arrays

AbstractElectron emission characteristics of field emitter arrays (FEAs) as etched shape of gate‐insulating opening were investigated by the measurement of anode and/or gate leakage current and voltage. In this study, we introduced a hybrid etching process, which etches the gate insulator wet and dry process sequentially. We also compared electron emission characteristics of FEAs as a function of etching process to form the gate‐insulating opening. The current density of field emitter arrays (FEAs) with new type of gate‐insulating opening is lower than that of FEAs with vertically etched shape of gate‐insulating opening. The electric field of FEAs made by hybrid process is higher than that of FEAs by using wet etching process to form the gate‐insulating opening. Thus, introduced hybrid‐etching process can optimize the gate‐insulating opening of FEAs.

Electron emission characteristics of boron nitride films synthesized by plasma-assisted chemical vapor deposition

Boron nitride (BN) films are synthesized using BCl3 and N2 as source gases by plasma-assisted chemical vapor deposition. The BN film consists of hexagonal grains of 3 nm in size. The energy gap is estimated to be as wide as 6.0 eV from ultraviolet-visible optical transmission measurement. The electrical resistivity is estimated to be 2×1011 and 1.3×102 Ω cm for undoped and sulfur-doped BN films, respectively. The electron emission current is detected at electric fields higher than 9 V/μm. The tunneling barrier height is estimated to be 0.1 eV from the Fowler–Nordheim plot. BN-coated Si tip field emitter arrays are fabricated. The electron emission occurs at electric field as low as 6 V/μm. It is demonstrated that the electron emission characteristic of Si tip array is much improved by BN coating.

Fabrication of microelectron gun arrays using laser micromachining

We have successfully fabricated miniaturized field emission tip arrays with microcolumns using microfabrication technology and laser micromachining. The nanosize Si-tip arrays with 20nm radii were fabricated using conventional microfabrication techniques such as an isotropic reactive ion etching(RIE), a sharpening oxidation procedure, etc. The microcolumns were fabricated using laser micromachining techniques. Preparatory laser micromachining has been performed on the various materials such as Si wafer, Mo, Ta and 304 stainless steel. Various holes with radii ranging from 2 to 100 micron on these materials were successfully fabricated using TEM 00 Yag:Nd 3+ laser. The patterns of electron beams through the laser-fabricated microcolumns were observed using a micro channel plate and a charge coupled device (CCD) camera.

Characteristics on the Gate Insulator of Metal Tip Field Emitter Arrays after Wet Etching Process

The effect of wet-etching process on the gate insulator for fabrication of field emitter arrays (FEAs) was examined. Three types of wet-etching process have been performed to fabricate metal tip FEAs, they are Mo (gate metal), oxide (gate insulator) and Al (release layer) etching, respectively. We examined the effect of gate insulator after wet etching through breakdown field strength and rms surface roughness. And the effect by residual ions or atoms was also examined. The breakdown field strength of gate insulator by the measurement of current-voltage for immersing in oxide etchant was rapidly lowered at the expense of large etching time. However in case of Al etchant, the breakdown field strength was lowered slowly. In all cases, it has been validated through Auger electron spectroscopy (AES) analysis that the residual atom was phosphor after wet-etching process when compared cleaned with non-cleaned samples. Also, we obtained excellent result when aluminum etchant was substituted for 3% tetra-methyl ammonium hydroxide (TMAH). In case of TMAH, decrease of the breakdown field strength was the slowest, surface roughness was smoother, and it did not attack gate and tip material.

Ultra sharp crystalline silicon tip array used as field emitter

This article describes the fabrication of single crystal silicon field emission tip arrays. Each array consists of 2500 tips. We used 4 in. (100) oriented n type silicon wafers 0.008 – 0.020 Ωcm, Sb doped. The tips were formed using a RIE process. We achieved crystalline emitter tip radiuses of 1.5 – 2 nm. The extraction grid is a self aligned, sputter deposited Ti0.1W0.9 film. The radiuses of the extraction grid apertures range from 300 to 150 nm and have a tip to tip spacing from 10 to 5 μm. The testing was done in vacuum with a distance of 500 μm between extraction grid and anode. We have seen maximum stable array currents up to 2 μA. An anode current of 10 nA was initially detected at a minimal gate bias of about 14 V.

Self-aligned silicon field emission cathode arrays formed by selective, lateral thermal oxidation of silicon

This article reports on the fabrication of single crystal silicon, field emission tip arrays. The tips are formed by exposing a ‘‘capped’’ silicon pedestal to a lateral high temperature thermal oxidation. Tips formed using this process have uniform height and profile, and have small radii of curvature—typically less than 20 nm. We have fabricated tip arrays with up to 2500 elements and with the tip-to-tip spacing ranging from 1.0 to 5.0 μm. The thermal SiO2 has a nominal thickness of 600 nm and serves as insulation between the extraction grid and the substrate. The extraction grid is a self-aligned, sputter deposited Ti0.1W0.9 film. Extraction grid apertures range from 900 nm to 1.7 μm. The process sequence is flexible allowing the fabrication of tips with different heights. The vertical position of the tip apex with respect to the extraction grid aperture, therefore, is a controllable parameter. The preliminary emission measurements are presented here for arrays containing 400 elements. All testing is done in ultrahigh vacuum (typically less than 5.0×10−10 Torr). The areas of the arrays fabricated range from 40 μm×40 μm to 100 μm×100 μm. The tip heights range from 1.0 to 1.4 μm above the substrate silicon. The maximum current produced from a 400 element array is only 0.45 μA at 140 Vdc. The low array current indicates that only a small number of tips are active at a given voltage.