Jonghyun Moon

Low work function nanometer-order controlled transfer mold field-emitter arrays

Extremely sharp and uniform Transfer Metal Mold FEAs with thin film low work function and environment-hard emitter material such as TiN and Au have been fabricated by controlling the thickness of the coated emitter material to realize high efficient, high reliable, low-cost vacuum nanoelectronic devices, and especially aerospace nanodevices for electric propulsion engines [1, 2]. Their nanometer order tip radii from 2.5 to 52.5 nm can be controlled by changing the thickness of emitter materials. Turn-on electric fields of the Au- FEAs from 31.8 to 68.1 V/μm (Emitter/anode distance: less than 30 μm) have been intentionally controlled by changing tip radii. Turn-on field of TiN-FEAs resulted in the low electric field values of 21.7 V/μm.

Suitability of low-work-function titanium nitride coated transfer mold field-emitter arrays for harsh environment applicationsa)

Low-work-function titanium nitride (TiN) coated transfer mold field-emitter arrays (TiN-FEAs) were fabricated by the transfer metal mold method. This method has potential for realizing stable large-area aerospace nanodevices that are resistant to the harsh plasma atmospheres often experienced by electric propulsion engines in space. Another application is for production of vacuum nanoelectronic devices such as field-emission displays that are suitable for highly oxidizing atmospheres. TiN-FEAs have sharp tips with radii of 6.8 nm, and their work function is just 3.2 eV compared to approximately 5.0 eV for conventional emitter materials such as carbon nanotubes. The turn-on fields of TiN-FEAs are as low as 15.4 V/μm, and their anode-to-emitter distance is 10 μm. Field-emission characteristics of TiN-FEAs were evaluated in situ at a pressure as high as 10−3 Pa and by irradiation with oxygen radicals at 1015 cm−2 s−1, a flux several orders of magnitude higher than orbital satellites typically experience. As ...

Stable, ruggedized, and nanometer-order size transfer mold field emitter array in harsh oxygen radical environment

Extremely sharp, uniform, stable, rugged, low operating voltage, and nanometer size molybdenum field emitter arrays (Mo FEAs) were developed by transfer mold fabrication. These can be used in stable and reliable vacuum nanoelectronic devices such as those used in electric propulsion engines and in environmentally demanding applications. Nanometer size transfer mold Mo FEAs were fabricated with base lengths of 36–370 nm. The 36 nm base length transfer mold Mo FEAs are the smallest FEAs ever reported. The tip radii were as sharp as 2.8–3.5 nm. The turn-on fields of the transfer mold Mo FEAs with a base length of 36–370 nm were found to be as low as 9.0–23.6 V/μm for the short anode-to-apex distance of less than 10 μm. These are lower than those of conventional FEAs such as carbon nanotube FEAs, Spindt-type FEAs, and Gray-type FEAs with approximate turn-on fields of 50–600 V/μm. They can thus be used in reliable vacuum nanoelectronic devices. The emission fluctuation of the 36 nm base length transfer mold ...

Nanometer-order base length, sharp and uniform field emitter arrays fabricated by transfer mold method

Nanometer-order base length, sharp and uniform field emitter arrays with 64 nm base length and 2.5 nm tip radius, which is the smallest and sharpest FEAs ever reported, have been developed by Transfer Mold method to realize the uniform and stable field emission characteristics.

Aerospace environmental stability of nanostructured transfer mold amorphous carbon field emitter arrays

Sharp, low operation voltage, and nanostructured amorphous carbon (a-C) field emitter arrays (FEAs) have been fabricated by Transfer Mold emitter fabrication method to realize the highly stable and reliable environment-hard vacuum nanoelectronic devices such as electric propulsion engines in aerospace, field emission displays (FEDs) and high-power conversion devices. The Transfer Mold a-C FEAs had the emitter base lengths of 41-1570 nm. The 41 nm FEAs is one of the smallest one, ever reported. Average tip radii were as sharp as 2.8-7.8 nm. The turn-on fields at the short distance of 10 μm between anode and emitter, are as low as 10.2-17.5 V/μm. The emission fluctuation rates, without radical treatment, of the 41 nm FEAs with no resistive layer, were as low as ±1.6%, which is one of the lowest value ever reported, compared with 5-several hundred % of the conventional FEAs. Moreover, Transfer Mold a-C FEAs exhibit the extremely stable fluctuations of less than ±4.5-4.8% in the oxygen radical atmospheres having highly reactive properties and fluxes (1015 atoms-cm-2s-1) with 107-108 orders of magnitude higher than typical fluxes (107-108 atoms-cm-2s-1) at aerospace environments. Thus, the nanostructured Transfer Mold a-C FEAs might be expected for the highly efficient and reliable vacuum electronic devices such as electric propulsion engines for aerospace applications to a great extent.

Stable emission characteristics of nanometer-order size Transfer Mold field emitter arrays with in-situ radical treatment

Extremely stable, sharp, uniform, low operation voltage and nanometer-order size field emitter arrays (FEAs) have been developed by Transfer Mold fabrication method to realize reliable vacuum nanoelectric devices such as electric propulsion engines and environment-hard applications. Nanometer-order Transfer Mold Mo FEAs have been fabricated with the base lengths of 36-370 nm, which value of 36 nm is the smallest value ever reported. The emission fluctuations of Transfer Mold Mo FEAs without resistive layers and without in situ radical treatment, were ±1.6%, which is the lowest value ever reported. In this study, the field-emission characteristics of Transfer Mold FEAs have been evaluated by the in-situ oxygen radical treatment having the flux of 1015 atoms·cm-2·s-1, which is 107-108 times higher than typical fluxes experienced at the LEO. The emission fluctuations without resistive layer and with in-situ oxygen radical treatment were as low as ±4.5%, which is compared with 5-100% for conventional FEAs with resistive layers and without highly oxidizing atmospheres. The work functions (4.8-5.3 eV) of Transfer Mold Mo FEAs with radical treatment, which were calculated from slope of FN plot and the geometric factor, almost coincide with the work function (5.2 eV) measured from UPS. Thus, the Transfer Mold Mo FEAs have resistance to highly oxidizing environments, exhibiting very stable emission characteristics. Therefore, the Transfer Mold Mo FEAs can be used to make highly efficient and reliable vacuum electronic devices in harsh environments.

Extremely stable and harsh-environment devices by Transfer Mold field emitter fabrication method

Extremely stable and harsh-environment devices have been fabricated by Transfer Mold emitter fabrication method and by using amorphous carbon (a-C) as an emitter material to realize the vacuum nanoelectronic devices such as electric propulsion engines, power switching devices and field emission displays (FEDs) in harsh environments, for example, in strong radical atmospheres of space, in high and low temperature atmospheres, and in oxidation gas atmospheres during FEDs fabrication process. Transfer Mold a-C FEAs exhibit the most stable field emission characteristics having the emission fluctuation ratio of ±1.62%, which is the lowest values ever reported. Panel and pixel electric thrusters by using Transfer Mold FEAs have been proposed. These electric thrusters make it easy to produce large and small thrusters. The Transfer Mold a-C FEAs exhibit very stable field-emission characteristics and the highest resistance to harsh environments. Therefore, they can be used to make highly efficient and reliable vacuum electronic devices such as electric propulsion engines and FEDs that are manufactured by using various reactive gases and highly oxidizing atmospheres.

Stable vacuum electronic devices for aerospace and environment-hard applications

Stable vacuum electronic devices have been fabricated by the Transfer Mold fabrication method to realize electric propulsion engines in harsh environments such as strong radical atmospheres in space for aerospace and environment-hard applications. The Transfer Mold field emitter arrays (FEAs) are extremely sharpened to 6.8 nm of tip radii and extremely uniform. The turn-on fields of low work function Transfer Mold FEAs at the short distance of 10 μm between anode and emitter are as low as 15.4 V/μm. The emission fluctuation rates without resistive layer, were as low as ±1.7%, which is one of the lowest value ever reported, compared with 5-several hundred % of the conventional FEAs. Moreover, sharp and uniform Transfer Mold FEAs having not only low work function but also environment-hard characteristics, exhibit the extremely stable fluctuations of less than ±5.1% even under the in-situ oxygen radical treatment. Therefore, the extremely stable and environment-hard Transfer Mold FEAs might be expected for the highly efficient and reliable vacuum electronic devices such as electric propulsion engines for aerospace applications to a great extent. Also, the panel type and pixel type electric thrusters have been proposed using Transfer Mold FEAs, having ion emitter arrays and electron emitter arrays whose electrons can neutralize positively charged particles. The panel type and pixel type electric thrusters give the easiness of getting large and small size thruster.

P2–22: Stable emission characteristics for low work function titanium nitride transfer mold field emitter arrays in harsh environment

Low work function titanium nitride (TiN) Transfer Mold field emitter arrays (TiN-FEAs) have been fabricated by combining the Transfer Metal Mold fabrication method and the emitter material coating method to realize stable vacuum nanoelectronic devices and aerospace nanodevices for electric propulsion engines in the harsh environment such as strong plasma and radical atmospheres. The average tip radii and standard deviations of tip radii of TiN-FEA were 6.8 nm and 1.9 nm, respectively. Therefore, TiN-FEA exhibited an extreme sharpness and high uniformity. The turn-on field of TiN-FEAs was as low as 15.4 V/µm at the short distance of less than 10 µm between anode and emitter. Turn-on fields of Ni-FEAs showed the 4.0 times increase from 14.9 V/µm to 59.4 V/µm with the increase of the in-situ oxygen radical treatment time. However, turn-on fields of TiN-FEAs showed the 1.2 times increase from 15.4 V/µm to 18.8 V/µm. The fluctuation rate of Ni-FEA with or without radical treatment was as low as less than ±10% and ±4%. However, those of TiN-FEA with or without radical treatment were as low as less than ±5.1% and ±2.5%, respectively. Therefore, the TiN-FEAs exhibit stable field emission characteristics in harsh environments.

P1–16: Low operation voltage nanometer base length, sharp and uniform transfer mold field emitter arrays

Low operation voltage nanometer-order base length, extremely sharp and uniform field emitter arrays with 190 nm base length, 3.5 nm tip radius and 8 V/µm turn-on field at the short distance of less than 10 µm between anode and emitter, which is one of the lowest turn-on fields FEAs ever reported and is almost similar to the theoretical limit of 4.5 eV for the molybdenum work function value, have been developed by Transfer Mold method to realize the uniform field emission characteristics.