Yuning Sun

Fabrication of carbon nanotube emitters on the graphite rod and their high field emission performance

Carbon nanotube (CNT) emitters with small emission area were fabricated on graphite rods using CNT films. By introducing the edge polishing process, the field emission performance of the CNT emitter was much improved, which showed a very high emission current of 6.34 mA (1.6 A/cm2) under an applied electric field of 5.3 V/μm. It also indicates good long-term emission stability, which reveals no degradation in the emission current for 20 h. The emission patterns demonstrate uniform and well-focused electron beam spots. The enhanced field emission performance is mainly attributed to the suppressed edge emission after the edge polishing process.

Excellent oxidation endurance of boron nitride nanotube field electron emitters

Boron nitride nanotubes (BNNTs) are considered as a promising cold electron emission material owing to their negative electron affinity. BNNT field emitters show excellent oxidation endurance after high temperature thermal annealing of 600 °C in air ambient. There is no damage to the BNNTs after thermal annealing at a temperature of 600 °C and also no degradation of field emission properties. The thermally annealed BNNTs exhibit a high maximum emission current density of 8.39 mA/cm2 and show very robust emission stability. The BNNTs can be a promising emitter material for field emission devices under harsh oxygen environments.

Field emission behavior of carbon nanotube field emitters after high temperature thermal annealing

The carbon nanotube (CNT) field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm2. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.

High-Performance Field-Emission Properties of Boron Nitride Nanotube Field Emitters

Boron nitride nanotubes (BNNTs) have attracted considerable attention as a field emission material because of their high mechanical strength, high negative electron affinity, and high oxidation resistance. Nevertheless, the obtained field-emission properties of BNNTs have indicated poor emission performance, which is a very high turn-on electric field with a low emission current. We fabricated BNNT field emitters and investigated their field-emission properties. The field-emission properties of the BNNT field emitters were considerably enhanced compared to those of other BN nanomaterial-based field emitters. The turn-on and the threshold electric fields of the BNNT field emitter were 3.1 and 5.4 V/μm at the gap distance of 750 μm, respectively. Both the turn-on and the threshold electric fields of the BNNT field emitters were decreased by increasing the gap distance between the emitter tip and the anode electrode. Degradation of the emission current during field emission operation for 20 h showed no significant difference according to the gap distance. Emission current fluctuation of the BNNT field emitters showed that the smaller gap was more unstable than the larger gap. The enhanced emission properties are mainly attributed to the small diameter, high-quality, and straight structure of BNNTs as well as the stable network formation of the BNNT film with good mechanical and electrical contact between the BNNTs and the cathode electrode. The remarkable emission performance of the BNNT field emitters might have promising applications for various field-emission devices.

Precise Patterning of Organic Single Crystals via Capillary-Assisted Alternating-Electric Field

Owing to the extraordinary properties, organic micro/nanocrystals are important building blocks for future low-cost and high-performance organic electronic devices. However, integrated device application of the organic micro/nanocrystals is hampered by the difficulty in high-throughput, high-precision patterning of the micro/nanocrystals. In this study, the authors demonstrate, for the first time, a facile capillary-assisted alternating-electric field method for the large-scale assembling and patterning of both 0D and 1D organic crystals. These crystals can be precisely patterned at the photolithography defined holes/channels at the substrate with the yield up to 95% in 1 mm2 . The mechanism of assembly kinetics is systematically studied by the electric field distribution simulation and experimental investigations. By using the strategy, various organic micro/nanocrystal patterns are obtained by simply altering the geometries of the photoresist patterns on substrates. Moreover, ultraviolet photodetectors based on the patterned Alq3 micro/nanocrystals exhibit visible-blind photoresponse with high sensitivity as well as excellent stability and reproducibility. This work paves the way toward high-integration, high-performance organic electronic, and optoelectronic devices from the organic micro/nanocrystals.

Silicon based micro-scale metal grid for field emission device

For application to electron field emission devices, a metal grid based on a silicon frame is introduced. Silicon frame is used to improve the thermal resistivity and electrical stability by electron beam. Silicon based micro-scale metal grid fabricated using MEMS technology.

Silicon-based metallic micro grid for electron field emission

A micro-scale metal grid based on a silicon frame for application to electron field emission devices is introduced and experimentally demonstrated. A silicon lattice containing aperture holes with an area of 80 × 80 µm2 and a thickness of 10 µm is precisely manufactured by dry etching the silicon on one side of a double-polished silicon wafer and by wet etching the opposite side. Because a silicon lattice is more rigid than a pure metal lattice, a thin layer of Au/Ti deposited on the silicon lattice for voltage application can be more resistant to the geometric stress caused by the applied electric field. The micro-fabrication process, the images of the fabricated grid with 88% geometric transparency and the surface profile measurement after thermal feasibility testing up to 700 °C are presented.

Field emission properties of GNP emitters dependent on gap between anode and cathode

We fabricated graphite nanoplatelet (GNP) field emitters using graphite adhesive and graphite rod. Comparing the field emission properties for different gap, turn-on electric field and threshold electric field were decreased almost in half, and maximum current density was increased about half as many again. The long-term emission stability also shows better results in large gap more than small gap. We consider that it is due to decreased effects of local vacuum and outgassing in spite of high local electric field. These properties indicate that GNP field emitters could be robust field emitters.

High emission performance of carbon nanotube paste field emitters fabricated by graphite filler

We demonstrated high field emission performance of carbon nanotube paste emitters, which were fabricated by using graphite filler, instead of commonly used metal or SiO2, or SiC particle fillers. The emitter with an emission area of 0.7 mm in diameter shows a highest current of 8.4 mA before electrical arcing events, corresponding to a current density of 2.2 A/cm2. The emitter shows a stable current of 1 mA for 20 h. It is suggested that the paste emitter could be a good candidate for x-ray source applications.

High performance field emission of carbon nanotube field emitters fabricated on a graphite rod after thermal annealing

We demonstrated high performance field emission of carbon nanotube (CNT) field emitters fabricated on a graphite rod. After the thermal annealing at 900 °C in vacuum ambient, the emitter showed a high emission current of 11.3 mA, corresponding to an emission current density of 5.8 A/cm2. The CNT emitter indicated a low turn-on field of 1.9 V/μm and stable emission stability at a current of 1 mA. In addition, it also showed a small and uniform emission pattern at the phosphor coated ITO glass. The CNT field emitter can be a good candidate for X-ray source applications.